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An Introduction to Vehicle Networks, Scan Tools, and

MultiplexingPresented by: Paul Baltusis

Powertrain Control System Engineering Diagnostic Systems Department OBD-II Technical Specialist Revised: September 28, 2002


In-Vehicle Networks

• In-vehicle networking, also known as multiplexing, is a method for transferring data between electronic modules via a serial data bus.


Benefits of Networking• Eliminates redundant sensors and dedicated

wires for each function (lower cost, lower weight, better reliability)

• Reduces number of wires and connectors (lower cost, lower weight, better reliability, easier-to-package wiring harness)

• Allows more features and more flexibility (modules share data, more flexible design and vehicle option content)

• Allows adding features via software upgrades


Benefits of Networking


Networking Methods

• Class A – Generic UART (Universal Asynchronous Receiver/Transmitter) or other custom low speed device < 10 Kbps.

• Class B – Medium speed, for example J1850, between 10 Kbps and 125 Kbps (Ford DCL and SCP, GM Class 2)

• Class C – High Speed, for example CAN 2.0, between 125 Kbps and 1,000 Kbps (Controller Area Network)


OBD Communication Protocols

• OBD-II and EOBD regulations define the communication protocols that can be used for diagnostics.

• The intent was to reduce the proliferation of manufacturer-specific protocols used for diagnostics.

• This would lead to more generic, less expensive scan tools.



• ISO 9141-2 (K-Line)• ISO 14230-4 (Keyword Protocol 2000)• J1850 41.6 Kbps Pulse Width Modulated• J1850 10.4 Kbps Variable Pulse Width• J2284/ISO 15765-4 (CAN)



• Only one OBD-compliant link may be brought out to the J1962 Data Link Connector

• OBD-II allows only 500 kbps CAN, EOBD allows 250 and 500 kbps.

• CARB will force all manufacturers to use CAN for the 2008 MY

• J2534 (pass through reprogramming) must use a generic OBD link.


Controller Area Network

•CAN is a network protocol used to interconnect a network of electronic control modules or “nodes”.•Typically, a two wire, twisted pair cable is used.•CAN has a stringent set of rules, implemented in the CAN chip, that supports the serial transfer of information between two or more nodes.


CAN Network

Where does CAN fit in the range of networks?

Networks are usually based on size:WAN – Wide Area Network (Internet)

LAN – Local Area Network (Ethernet)

SAN – Small Area Network (CAN)


CAN• CARB allows the use of CAN for 2003 MY and

beyond vehicles. • EOBD allows the use of CAN for 2001 CY and

beyond vehicles.• Some US manufacturers are planning to start

using CAN starting on some vehicles in the 2003 MY.

• CARB requires the use of CAN on all vehicles for the 2008 MY and beyond.


CAN• CAN messages have a specified structure that

is specified in CAN standards.• CAN networks have rules (bitwise arbitration)

for dealing with colliding messages when two modules start transmitting messages at the same time.

• There are two formats for addressing – 11 bit and 29 bit identifiers. 11-bit has a 2032 message limit, 29-bit allows for millions of distinct messages.


CAN – Basic Message Structure


CAN Message Arbitration


J1850 41.6 PWM• J1850 41.6 PWM is used by Ford. Ford

internally calls this protocol Standard Corporate Protocol (SCP)

• SCP is a true network protocol that incorporates bus arbitration.

• SCP is used for both vehicle network communication and diagnostic communication.


J1850 10.4 VPW

• J1850 10.4 VPW is used by General Motors. GM internally calls this protocol Class 2.

• Class 2 is a true network protocol that incorporates bus arbitration.

• Class 2 is used for both vehicle network communication and diagnostic communication.


ISO 9141

• ISO 9141 is used by many Japanese manufacturers.

• ISO 9141 is not a network protocol, it can only be used for diagnostics.

• There is no bus arbitration. It can be used to connect one diagnostic tool to a vehicle control module.

• ISO 9141 is relatively slow – 10.4 Kbps


KWP 2000• KWP is used by many European

manufacturers. It uses an enhanced set of diagnostic messages but retains the ISO 9141 physical layer.

• KWP is not a network protocol, it can only be used for diagnostics.

• There is no bus arbitration. It can be used to connect one diagnostic tool to one or more vehicle control modules.

• KWP is relatively slow – 10.4 Kbps


Types of Network Messages• There are two types of network messages

– Diagnostic messages– Normal Mode messages

• Normal Mode messages are used to share information between modules on the network during normal vehicle operation, e.g. instrument cluster sends fuel level info (percent fill) to PCM.

• Normal mode messages always use physical addressing.


Types of Network Messages• Diagnostic Mode messages are used to

communicate between a test tool and a module on the network.

• Diagnostic messages can use either physical addressing or functional addressing.

• Manufacturer-specific tools normally use physical addressing

• Generic OBD tools use functional addressing because the configuration of the network and network addresses do not have to be known for every specific vehicle


SAE/ISO Diagnostic Specifications• Vehicle diagnostic communication

specifications have been written by the Society of Automotive Engineers (SAE) and by various International Standards Organization (ISO) workgroups.

• These standards are referenced by the California, Federal and European OBD regulations.

• US regulations reference SAE standards, European regulations reference equivalent ISO standards.


SAE/ISO Diagnostic SpecificationsLegislated diagnostics• SAE J1930/ISO 15031-2 – Electrical/Electronic Systems

Diagnostic Terms, Definitions, Abbreviations and Acronyms• SAE J1962/ISO 15031-3 – Diagnostic Connector• SAE J1978/ISO 15031-4 – OBD-II Scan Tool• SAE J1979/ISO 15031-5 – E/E Diagnostic Test Modes• SAE J2012/ISO 15031-6 – Diagnostic Trouble Codes• SAE J2186/ISO 15031-7 – E/E Data Link SecurityNon legislated diagnostics• SAE J2190/ISO 14229 – Enhanced E/E Diagnostic

Test Modes


SAE/ISO Multiplex SpecificationsLegislated multiplex standards• SAE J1850 (Class B Data Comm. Network

Interface)• ISO 9141-2 (K-Line)• ISO 14230-4 (Keyword Protocol 2000)• SAE J2284/ISO 15765-4 (CAN)• J2534 – Recommended Practice for Pass-Thru

Vehicle Programming


SAE J1930 – Terms and Acronyms• J1930 attempts to limit the proliferation of

terms, abbreviations and acronyms used in motor vehicle service literature.

• Examples– Ford uses ECT (engine coolant temp sensor), GM

uses CTS (coolant temp sensor), J1930 uses ECT– Ford uses ISC (idle speed control), J1930 uses IAC

(idle air control)– Ford uses EEC-V, J1930 uses PCM (powertrain

control module)


SAE J1930 – Terms and Acronyms• J1930 describes a consistent methodology for

naming components and systems.

MODIFIERS BASE WORDWhat is Where Which What does What

Purpose? Is it?Temp? it sense? Is it?

Sensor (most generic)

Temperature Sensor

Coolant Temperature Sensor

Engine Coolant Temperature Sensor

Instrumentation Engine Coolant Temperature Sensor (most specific)

Least <<<<<< SIGNIFICANCE>>>>>> Most


SAE J1962 – Data Link Connector

• J1962 describes the functional requirements for the vehicle and test tool data link connector (DLC):– In-vehicle location/access– Connector design– Terminal assignments– Electrical interface requirements


SAE J1962 – Data Link Connector• The 16-pin DLC assignments are specified in

SAE J1962/ISO 15031-3Pin 1 - Discretionary Pin 9 – Discretionary

Pin 2 – Bus + J1850 Pin 10 – Bus – J1850

Pin 3 – Discretionary Pin 11 – Discretionary

Pin 4 – Chassis Ground Pin 12 – Discretionary

Pin 5 – Signal Ground Pin 13 - Discretionary

Pin 6 – CAN High Pin 14 – CAN Low

Pin 7 – K-Line ISO9141/KWP Pin 15 – L-Line ISO9141/KWP


SAE J1962 – Data Link Connector• The general location of the DLC is specified in

J1962, however, CARB and EPA regulations are more restrictive.

• CARB specifies that DLC must be on driver’s side of vehicle centerline, not on center console, or behind storage accessories.

• A covered DLC must have label (e.g. OBD) approved by CARB.

• Pin 16 must have < 20 Volts (not 24 or 42 V)


SAE J1978 – Generic Scan Tool• J1978 defines the minimum functionality

required by an “OBD-II Scan Tool”– Automatic hands-off determination of the

communication interface– Displays status and results of on-board diagnostic

evaluations– Displays pending and confirmed DTCs– Displays current data, freeze frame data, and

vehicle information– Clears DTCs, test results and freeze frame– Provides a user manual/help facility


SAE J2012 – Diagnostic Trouble Codes• J2012 defines a set of diagnostic trouble

codes (DTCs) where industry uniformity has been achieved.

• DTCs consist of an alpha character followed by four characters– Pxxxx is reserved for powertrain DTCs– Bxxxx is reserved for body DTCs– Cxxxx is reserved for chassis DTCs– Uxxxx is reserved for network DTCs


SAE J2012 – Diagnostic Trouble Codes• The second character designates whether the

DTCs and a generic SAE DTC or a manufacturer-specific DTC.

• P0xxx, P2xxx, P3400, and U0xxx are generic DTCs

• P1xxx, P30xx, P3100, P32xx and P33xx are manufacturer-specific DTCs

• The remaining characters designate the system associated with the fault. The characters are hex and can range from 0 – F.


SAE J2012 – Diagnostic Trouble Codes• The J2012 committee defines new DTCs on a

quarterly basis, based on manufacturer requests.

• The J2012 committee assigns DTCs in a uniform manner using J1930 terminology.

• Sample output:P2632 – Fuel Pump B Control Circuit / Open

P2633 – Fuel Pump B Control Circuit Low

P2634 – Fuel Pump B Control Circuit High

P2636 – Fuel Pump B Low Flow/Performance


SAE J2012 – Diagnostic Trouble Codes• Sample input:P0A00 – Motor Electronics Coolant Temp Sensor Circuit

P0A01 – Motor Electr. Coolant Temp Sensor Circuit Range / Performance

P0A02 – Motor Electr. Coolant Temp Sensor Circuit Low

P0A03 – Motor Electr. Coolant Temp Sensor Circuit High

P0A04 – Motor Electr. Coolant Temp Sensor Circuit Intermittent / Erratic

• Sample network DTCs:U0001 – High Speed CAN Communication Bus

U0101 – Lost Communication with TCM

U0302 – Software Incompatibility with TCM


SAE J2186 – Data Link Security• J2186 defines a method to access secured

vehicle controller functions.• Three parameters control security access

– the “seed” (sent by controller) and “key” (sent by external device)

– the delay time (minimum delay time between attempts)

– the number of false access attempts


SAE J1979 – Diagnostic Test Modes

• SAE J1979/ISO 15031-5 defines standard diagnostic test modes.

• Diagnostic/emission critical control modules must implement these diagnostic test modes. They must be on the OBD data link or must use another module as a gateway.

• CARB defines engine and transmission control modules as emission-critical.


SAE J1979 – Diagnostic Test Modes

• Any other control module that performs a major OBD-II monitor or performs CCM monitoring for more than two components is considered to be diagnostic critical.

• If a diagnostic/emission critical control module is reprogrammable, it must respond with Mode $09 CALID and CVN.

• It must be able to be reprogrammed using a SAE J2534 interface.


SAE J1979 – Diagnostic Test Modes• J1979 specifies a set of standard messages

that can be used by scan tool to obtain OBD-II data from a vehicle. (Modes $01 to $09)

• Functional addressing is used instead of physical addressing for all messages because the test tool does not know which systems on the vehicle have the OBD information that is requested.

• Response times to messages are specified.• Message lengths are specified.


SAE J1979 – Diagnostic Test Modes• Messages must utilize a standard set of

header bytes specified for each communication protocol.

• The remainder of the message (the data bytes) specify the type of message (test mode) and specific data that is being requested.

• Header byte definitions are specified on the next two slides.


SAE J1979 – Header Bytes

H e a d e r b y t e s C A N f r a m e d a t a f i e l d

CAN Identifier (11 or 29 bit) #1 PCI Byte

#2 #3 #4 #5 #6 #7 #8


SAE J1979 – CAN Header Bytes

C A N i d e n t i f i e r ( h e x )

D e s c r i p t i o n ( 1 1 - b i t a d d r e s s i n g )

7 D F C A N i d e n t i f i e r f o r f u n c t i o n a l l y a d d r e s s e d r e q u e s t m e s s a g e s s e n t b y t h e e x t e r n a l t e s t e q u i p m e n t .

7 E 0 P h y s i c a l r e q u e s t C A N i d e n t i f i e r f r o m t h e e x t e r n a l t e s t e q u i p m e n t t o E C U # 1

7 E 8 P h y s i c a l r e s p o n s e C A N i d e n t i f i e r f r o m E C U # 1 t o t h e e x t e r n a l t e s t e q u i p m e n t


7 E 9 P h y s i c a l r e s p o n s e C A N i d e n t i f i e r f r o m E C U # 2 t o t h e e x t e r n a l t e s t e q u i p m e n t


7 E A P h y s i c a l r e s p o n s e C A N i d e n t i f i e r f r o m E C U # 3 t o t h e e x t e r n a l t e s t e q u i p m e n t


7 E B P h y s i c a l r e s p o n s e C A N i d e n t i f i e r f r o m E C U # 4 t o t h e e x t e r n a l t e s t e q u i p m e n t


7 E C P h y s i c a l r e s p o n s e C A N i d e n t i f i e r f r o m E C U # 5 t o t h e e x t e r n a l t e s t e q u i p m e n t


7 E D P h y s i c a l r e s p o n s e C A N i d e n t i f i e r f r o m E C U # 6 t o t h e e x t e r n a l t e s t e q u i p m e n t


7 E E P h y s i c a l r e s p o n s e C A N i d e n t i f i e r f r o m E C U # 7 t o t h e e x t e r n a l t e s t e q u i p m e n t


7 E F P h y s i c a l r e s p o n s e C A N i d e n t i f i e r f r o m E C U # 8 t o t h e e x t e r n a l t e s t e q u i p m e n t


Ford Module Addresses

Module Phys Adr Func Adr Rec Adr Xmit Adr Func Rec Adr Func Xmit Adr(J1850) (J1850) (CAN) (CAN) (CAN) (CAN)

PCM$10 $6A $7E0 $7E8 $7DF $7E8(Powertrain Control Module)

TCM$18 $6A $7E1 $7E9 $7DF $7E9(Transmission Control Module)

ABS $28 $6A $7E2 $7EA $7DF non-OBD(Anti-lock Brake System)

AHCM $0F $6A $7E3 $7EB $7DF non-OBD(Auxiliary Heater Control Module)

TCCM $18 $6A $7E4 $7EC $7DF non-OBD (Transfer Case Control Module)

AFCM $16 $6A $7E5 $7ED $7DF $7ED(Alternative Fuel Control Module)

SPCM $11 $6A $7E6 $7EE $7DF $7EE


Mode $01 – Retrieve Diagnostic Data

• Mode $01 provides diagnostic data, commonly called PIDs (Parameter ID)

• Service technicians can use the data to troubleshoot sensors, check OBD monitor completion, MIL status, etc.

• Test tool specifies the requested data by PID number ($00 through $FF)

• PIDs are defined in J1979 (number, units, conversion/scaling factor, acronym)

• PIDs must show “raw” values – not substituted values if a sensor fails


Mode $01 – Retrieve Diagnostic Data

The message format used to make a PID request is as follows:


PID $01 – I/M Readiness


PID $02 and $03


PIDs $04 - $11


PIDs $12 - $1B


PIDs $1C - $1E


PIDs $1F - $2B


PIDs $2C - $33


PIDs $34 - $3F


PID $41


PIDs $42 - $4E


Mode $02 – Freeze Frame

• Mode $02 stores Mode $01 PID data at the time a pending or confirmed DTC is stored.

• Fuel system and misfire DTCs have a higher priority and overwrite any existing data.

• Service technicians can use the data to understand the conditions at the time the malfunction occurred.

• Only one frame ($00) is required to be stored.



• Freeze frame can be useful, however, there are some caveats.

• Freeze frame is stored when the DTC is stored, not when the problem began.

• For circuit faults, it usually takes 5 seconds to store a DTC.

• Misfire is evaluated every 1,000 revs. A misfire DTC may be stored 60-90 seconds after the misfire initially occurred, at substantially different rpm and load conditions.



The message format used to retrieve freeze frame is as follows:


Mode $03 – Retrieve emission-related DTCs

• Mode $03 reports confirmed, emission-related DTCs.

• Service technicians and I/M test stations use this mode to determine what malfunction turned on the MIL.

• Mode $03 reports “history” codes for 40 warm-ups after the MIL is extinguished.


Mode $03 – Retrieve emission-related DTCs

The message format used to retrieve emission-related DTCs is as follows:


Mode $04 – Clear DTCs and Diagnostic Information

• Mode $04 clears/erases DTCs and resets diagnostic data at the time a pending or confirmed DTC was stored. Diagnostic data includes freeze frame, I/M readiness, monitor status, PIDs for MIL_DIST, WARM_UPS, CLR_DIST, Mode $06 data.

• Service technicians can use this mode to turn off the MIL after a repair and to validate a repair.


Mode $04 – Clear DTCs and Diagnostic Information

The message format used to clear DTCs is as follows:


Mode $05 – Retrieve Oxygen Sensor Data

• Mode $05 provides test results for oxygen sensors.

• This mode is no longer used for CAN applications. All data is still available using Mode $06.


Mode $05 – Retrieve Oxygen Sensor DataThe message format used to retrieve oxygen sensor data is as follows:


Mode $05 – Retrieve Oxygen Sensor Data

D a t a B y t e

D e s c r i p t i o n

2 W h i c h T e s t I D : $ 0 0 - T e s t I D ’ s s u p p o r t e d - o p t i o n a l ( $ 0 1 t o $ 2 0 ) $ 0 1 - R i c h t o l e a n s e n s o r t h r e s h o l d v o l t a g e ( c o n s t a n t ) $ 0 2 - L e a n t o r i c h s e n s o r t h r e s h o l d v o l t a g e ( c o n s t a n t ) $ 0 3 - L o w s e n s o r v o l t a g e f o r s w i t c h t i m e c a l c u l a t i o n ( c o n s t a n t ) $ 0 4 - H i g h s e n s o r v o l t a g e f o r s w i t c h t i m e c a l c u l a t i o n ( c o n s t a n t ) $ 0 5 - R i c h t o l e a n s e n s o r s w i t c h t i m e ( c a l c u l a t e d ) $ 0 6 - L e a n t o r i c h s e n s o r s w i t c h t i m e ( c a l c u l a t e d ) $ 0 7 - M i n i m u m s e n s o r v o l t a g e f o r t e s t c y c l e ( c a l c u l a t e d ) $ 0 8 - M a x i m u m s e n s o r v o l t a g e f o r t e s t c y c l e ( c a l c u l a t e d ) $ 0 9 - T i m e b e t w e e n s e n s o r t r a n s i t i o n s ( c a l c u l a t e d ) $ 0 A - $ 1 F - r e s e r v e d $ 2 0 - T e s t I D s s u p p o r t e d - o p t i o n a l ( $ 2 1 t o $ 4 0 )


Mode $06 – Retrieve OBD test results and malfunction limits

• Mode $06 provides monitoring test values and malfunction limits for various OBD monitors.

• Service technicians can use the data to see which monitors failed and by how much, or to validate repairs.

• Parts manufacturers can use this data to ensure replacement part compatibility.



•Mode $06 test values and limits are un-scaled, decimal numbers in J1850, ISO 9141-2 and ISO 1423-4. Manufacturers need to provide conversion factors for technicians to utilize this data. •ISO 15765-4 messages provide units and scaling as part of the message. Generic scan tools will be able to convert these to engineering units



The message format used to retrieve OBD test results is as follows:


Mode $06 – Retrieve OBD test results and limits

J1979 Secondary Air Mode $06 Data

Test ID Comp ID Description for J1850 Units

$30 $11 HO2S11 voltage for upstream flow test and rich limit volts


$31 $00 HO2S lean time for upstream flow test and time limit seconds

Monitor ID Test ID Description for CAN Units



$71 $82 HO2S lean time for upstream flow test and time limit seconds

Conversion for Test ID $30: multiply by 0.00098 to get volts

Conversion for Test ID $31: multiply by 0.125 to get seconds


Mode $06 – Retrieve OBD test results limits













J1979 DPFE EGR Hose Check Mode $06 Data


$42 $11 Delta pressure for upstream hose test and threshold in. H20

$42 $12 Delta pressure for downstream hose test and threshold in. H20

Conversion for Test ID $42: Take value, subtract 32,768, and then multiply result by 0.0078 to get inches of H20. The result can be positive or negative.

Monitor ID Test ID Description for CAN Conventional DPFE

$31 $80 Delta pressure for upstream hose test and threshold kPa

$31 $81 Delta pressure for downstream hose test and threshold kPa

J1979 EGR Flow Check Mode $06 Data


$49 $30 Delta pressure for flow test and threshold in. H20

$4B $30 EVR dutycycle for flow test and threshold percent

Conversion for Test ID $4B: multiply by 0.0000305 to get percent dutycycle.

Conversion for Test ID $49: Take value, subtract 32,768, then multiply result by 0.0078 to get inches of H20. The result can be positive or negative.

Monitor ID Test ID Description for CAN Conventional DPFE Units

$31 $85 Delta pressure for flow test and threshold kPa



Example of Mode $06:TestID CompID Test Value Min Max

$10 $11 Cat monitor switch ratio 45 0 48

Bank 1

$10 $21 Cat monitor Switch ratio 42 0 48

Bank 2

Conversion: multiply by 0.0156 to get a value from 0 to 1.0Bank 1 = 45 * 0.0156 = 0.702

Bank 2 = 42 * 0.0156 = 0.655

Threshold = 48 * 0.0156 = 0.749

This catalyst is about to fail. A normal 100K catalyst should have a 0 to 0.1


Mode $07 – Retrieve pending DTCs

• Mode $07 reports pending, emission-related DTCs.

• Starting in the 2005 MY, all pending DTCs must be reported, not just continuous pending DTCs.

• Staring in the 2005 MY, a pending DTC must be reported if the last monitoring cycle had a malfunction.

• Service technicians can use pending codes for faster validation or a repair.


Mode $07 – Retrieve pending DTCs

The message format used to retrieve pending, emission-related DTCs is as follows:


Mode $08 – Request on-board device control

• Mode $08 allows a service technician to invoke an on-board test mode.

• Only one test mode (Test ID $01) is currently defined. It allows a service or an I/M technician to seal the evaporative system for a pressure test.

• On Ford systems, this closes the canister vent solenoid for a 10 minute time duration.


Mode $08 – Request on-board device control

The message format used to request on-board device control is as follows:


Mode $09 – Retrieve vehicle information

• Mode $09 allows a service tech or I/M test technician to obtain vehicle VIN, module calibration number (CALID), Calibration Verification Number (CVN).

• VIN is required for 2005 MY, the vehicle can only report one VIN.

• CALID is required for 2005 MY. • A unique CALID is required for each emission-

related calibration on the vehicle. A unique CALID is required even if only a bit if data changes.


Mode $09 – Retrieve vehicle information (continued)

• A CVN must be supplied for each CALID• In 2005 MY, CVN must be calculated every

driving cycle and stored in Keep Alive Memory so that it can be retrieved with the engine off or engine running.

• CVN must not be erased by Mode $04.• CARB must approve CVN algorithm.• Manufacturers must provide CALID and CVN

information to facilitate I/M testing.


Mode $09 – Retrieve vehicle information (continued)

• Starting in the 2005 MY, CARB will require industry-standard counters that display how often OBD monitors run during real-world driving conditions as compared to a CARB-specified driving cycle.

• In-use performance counters will be required for catalyst, O2 sensor, EGR, secondary air, and evaporative system monitors.


Mode $09 – Retrieve vehicle informationThe message format used to retrieve vehicle information is as follows:

Info Type $02 is VIN, $04 is CALID(s), $06 is CVN(s), $08 is in-use performance counters


Inspection/Maintenance Readiness

• Many I/M test facilities will soon (Jan 1, 2002) be using OBD-II diagnostic information in place of tailpipe emissions tests.

• They will check MIL lamp, MIL status bit (PID 01, Data A, bit 7) and OBD monitor readiness (PID 01).

• For 2005 MY, they may check VIN, CALIDs and CVNs


Inspection/Maintenance Readiness (continued)

• CALIDs ensure that the correct (not recalled) software is on the vehicle.

• CVNs ensure that the module software was not tampered with.

• MIL status must not indicate “MIL on” during bulb prove out unless the MIL is being commanded on by a confirmed DTC.

• Monitor readiness bits must be in Keep Alive Memory


Inspection/Maintenance Readiness (continued)

• I/M readiness status may be displayed to the customer using the MIL.

• After 15-20 seconds of MIL prove out, the MIL can blink for 5-10 seconds if the vehicle is not ready for I/M testing.

• For the 2005 MY, CARB will require a scan tool communication validation of every production calibration using a J1699-3 tool.


SAE/ISO Diagnostic Specifications• Non-legislated diagnostic messages are

defined by SAE J2190 and ISO 14229• These are commonly referred to

“manufacturer-specific” test modes.• Manufacturers can use these messages to

perform manufacturer-specific tests and obtain manufacturer-specific data from any control module.

• Almost all manufacturers provide this info to the Equipment and Tool Institute (ETI), the consortium of scan tool manufacturers.


SAE/ISO Diagnostic Specifications• Common uses for these messages are:

– Obtain manufacturer-specific PIDs– Initiate on-board self-test– Obtain packets of PID data (rapid data)– Control module outputs– Reprogram flash memory– Configure modules

• The J2190 messages are very similar to the J1979 messages in structure and content.

• Only physical addresses are used, responses are required.


J2190 – Mode $13• Mode $13 reports all DTCs (emission and

non-emission, confirmed and pending.)• Very similar to Mode $03

Data Bytes (Hex) #1 #2 #3 #4 #5 #6 #7 Request all codes Request all powertrain DTCs (MIL, non-MIL, pending)

13

Report all codes Report all powertrain DTCs (MIL, non-MIL, pending)

53 Code #1 or 00 00

Code #2 or 00 00

Code #3 or 00 00

No codes to report, exit normally without results General Response 7F 13 00 00 00 62


J2190 – Mode $14• Mode $14 clears all DTCs.• Very similar to Mode $04

Data Bytes (Hex) #1 #2 #3 #4 #5 #6 #7 Request clear codes Request clear all codes, (MIL, non-MIL, pending)

14

Confirm codes clear Confirm all codes were cleared (individual clearing of codes not supported)

54

No codes to report, exit normally without results General Response 7F 14 data

byte #2 data byte #3

00 12


J2190 – Mode $22• Mode $22 is used to get PIDs. PID numbers, scaling

and units are defined by manufacturer and are specific to their individual systems.

• Very similar to Mode $01 Data Bytes (Hex) #1 #2 #3 #4 #5 #6 #7 Request data by PID Request PID Access 22 PID

(high byte)

PID (low byte)

Report data by PID Report PID Data 62 PID

(high byte)

PID (low byte)

data 1 (opt)

data 2 (opt)

data 3 (opt)

data 4 (opt)

Invalid PID requested, request not supported General Response 7F 22 data

byte #2 data byte #3

00 12


J2190 – Mode $23• Mode $23 is used to download data by direct

memory address.• Test tool gets raw data.

Data Bytes (Hex) #1 #2 #3 #4 #5 #6 #7 Request data by DMR Request DMR Access EEC-V

23 address (high byte)

address (mid byte)

address (low byte)

Report data by DMR Report DMR Data EEC-V

63 address (high byte)

address (low byte)

data 1 (opt)

data 2 (opt)

data 3 (opt)

data 4 (opt)

Invalid DMR requested, request not supported General Response 7F 23 address

(high byte or high word MSB)

address (mid byte or high word LSB)

00 12


J2190 – Mode $2A•Mode $2A is used to get a string of PIDs in one message; a “rapid packet”.•Used with Mode $2C to define rapid packet.


J2190 – Mode $30• Mode $30 is used to directly control module outputs

like shift solenoids, IAC, AIR pump, EGR, etc. (requires Mode $27 security access)

Data Bytes (Hex) #1 #2 #3 #4 #5 #6 #7 Perform parameter substitution Parameter Substitution 30 Chann.

ID Subst. Value high byte

Subst. Value low byte

Confirm diagnostic routine entered General Response 7F 30 Chann.

ID Subst. Value high byte

Subst. Value low byte

00

Invalid conditions, test running, or test not supported General Response 7F 31 Test # 00 00 31, 22,

33, or 12


J2190 – Mode $31• Mode $31 is used to request an on-board test, based

on test number.• Test Number On-demand Self Test Mode• $81 Key On Engine Off (gas and diesel)• $82 Key on Engine Running (gas and diesel)• $84 Output Test Mode (gas and diesel)• $88 Key On Engine Running Glow Plug Test (diesel)• $91 Key On Engine Off Injector Buzz Test (diesel)• $92 Key On Engine Running Cylinder Contribution Test (diesel)• $95 Key On Engine Running Switch Test (diesel) Data Bytes (Hex)

#1 #2 #3 #4 #5 #6 #7 Perform diagnostic routine by test number Diagnostic Routine Entry

31 Test #

Confirm diagnostic routine entered General Response

7F 31 Test # 00 00 00

Invalid conditions, test running, or test not supported General Response 7F 31 Test # 00 00 22, or

12


J2190 – Mode $36

• Mode $36 is used for reprogramming. (requires Mode $27 security access and Mode $34 Download Entry request)

Data Bytes (Hex) #1 #2 #3 #4 #5 #6 #7 Request to enter download mode Download Block Data 36 data 1 data 2

or 00 data 3 or 00

data 4 or 00

data 5 or 00

data 6 or 00

Not in download mode General Response

7F 36 data 1 data 2 data 3 22


J2190 – Mode $3F

• Mode $3F is used to indicate that the test tool is still online and prevent a diagnostic session time-out.

Data Bytes (Hex) #1 #2 #3 #4 #5 #6 #7 Tester Present Tester Present 3F Acknowledge tester General Response

7F 3F 00 00 00 00


J2190 – Mode $7F• Mode $7F is used by the control module to respond

to a test tool request. Data Bytes (Hex) #1 #2 #3 #4 #5 #6 #7 General acknowledge General Response 7F Data

byte #1 of request

Data byte #2 of request



Ackn or Reject code

Acknowledge or Reject Code: $00 - General affirmative $10 - General reject $11 - Mode not supported $12 - Invalid format, sub-function not supported $21 - Busy, repeat request $22 - Condition not correct, sequence error $23 - Routine not complete $31 - Request out of range $33 - Access denied, device secured $34 - Access granted $50 - Upload not accepted $61 - Normal exit with results $62 - Normal exit without results $63 - Abnormal exit with results $64 - Abnormal exit without results


J1979 Message Traffic Example Clear DTCs (Mode 04)

TX MSG: J1850PWM 61 6A F1 04

RX MSG: J1850PWM 01 6B 10 44

Request PIDs (Mode 01) [PID $00 defines which PIDs are supported ]

TX MSG: J1850PWM 61 6A F1 01 00

RX MSG: J1850PWM 01 6B 10 41 00 BF 9F B9 10

Request PID 04 (LOAD_PCT)

TX MSG: J1850PWM 61 6A F1 01 04

RX MSG: J1850PWM 01 6B 10 41 04 00 [LOAD_PCT = 0%]

Request PID 05 (ECT)

TX MSG: J1850PWM 61 6A F1 01 05

RX MSG: J1850[PWM 01 6B 10 41 05 4A [ECT = 74 deg F]

Request PID 11 (TP)

TX MSG: J1850PWM 61 6A F1 01 11

RX MSG: J1850PWM 01 6B 10 41 11 32 [TP = 19%]

Request PID 1C (OBD Type)

TX MSG: J1850PWM 61 6A F1 01 1C


J1979 Message Traffic ExampleRequest Mode 09 info

TX MSG: J1850PWM 61 6A F1 09 00 [request Mode 09 items supported]

RX MSG: J1850PWM 01 6B 10 49 00 01 FC 00 00 00

TX MSG: J1850PWM 61 6A F1 09 01

RX MSG: J1850PWM 01 6B 10 49 01 05 [number of VIN messages = 5]

TX MSG: J1850PWM 61 6A F1 09 02 [item 02 = VIN]

RX MSG: J1850PWM 01 6B 10 49 02 01 00 00 00 31

RX MSG: J1850PWM 01 6B 10 49 02 02 46 54 59 52

RX MSG: J1850PWM 01 6B 10 49 02 03 34 34 45 37

RX MSG: J1850PWM 01 6B 10 49 02 04 32 54 41 33

RX MSG: J1850PWM 01 6B 10 49 02 05 31 39 37 38 [VIN = 1FTYR44E72TA31978]

Request Pending DTCs (Mode 07)

TX MSG: J1850PWM 61 6A F1 07

RX MSG: J1850PWM 01 6B 10 47 01 13 01 02 00 00 [Pending DTC P0113, P0102 detected]


J1979 Message Traffic Example

Request Freeze Frame Support (Mode 02) [PID $00 defines which PIDs are supported ]

TX MSG: J1850PWM 61 6A F1 02 00 00

RX MSG: J1850PWM 01 6B 10 42 00 00 7F 98 00 00

Request Freeze Frame PID 02

TX MSG: J1850PWM 61 6A F1 02 02 00

RX MSG: J1850PWM 01 6B 10 42 02 00 01 13 [DTC that stored frame = P0113]

Request DTCs (mode 03)

TX MSG: J1850PWM 61 6A F1 03 [No response to OBD request, no DTCs]

Request DTCs (Mode 03)

TX MSG: J1850PWM 61 6A F1 03

RX MSG: J1850PWM 01 6B 10 43 01 13 00 00 00 00 [Stored DTC P0113 detected]


The End• I hope this presentation took some of

the mystery out of diagnostic scan tool communication.

• Thank you for your interest and attention!

Documents

An Introduction to Vehicle Networks, Scan Tools, and ...docshare01.docshare.tips/files/26206/262067554.pdf · An Introduction to Vehicle Networks, Scan Tools, and ... • ISO 14230-4