ELM329
Contents
Electrical Information
Using the ELM329
Pin Descriptions........................................................................... 3
Unused Pins.................................................................................5
Absolute Maximum Ratings......................................................... 5
Electrical Characteristics..............................................................6
Overview...................................................................................... 7
Communicating with the ELM329................................................ 7
AT Commands............................................................................. 9
AT Command Summary...............................................................9
AT Command Descriptions........................................................ 11
Reading the Battery Voltage...................................................... 25
OBD Commands........................................................................26
Talking to the Vehicle.................................................................27
Interpreting Trouble Codes........................................................ 29
Resetting Trouble Codes........................................................... 30
Quick Guide for Reading Trouble Codes................................... 30
Selecting Protocols.................................................................... 31
OBD Message Formats..............................................................32
Setting the Header / ID Bits........................................................34
ISO 157645-4 Message Types.................................................. 36
Multiline Responses...................................................................37
Receive Filtering - the CRA command.......................................39
Using the Mask and Filter.......................................................... 40
Monitoring the Bus..................................................................... 41
Mixed ID (11 and 29 bit) Sending...............................................42
Restoring Order..........................................................................43
Advanced Features
Using Higher RS232 Baud Rates...............................................44
Setting Timeouts - the AT ST and AT AT Commands............... 46
SAE J1939 Messages................................................................47
Using J1939............................................................................... 49
The FMS Standard.....................................................................52
Periodic (Wakeup) Messages.................................................... 53
Altering Flow Control Messages................................................ 54
Using CAN Extended Addresses............................................... 55
CAN (Single Wire) Transceiver Modes...................................... 56
Control Module Operation..........................................................56
Low Power Mode....................................................................... 57
Programmable Parameters........................................................60
Programmable Parameter Summary......................................... 61
Design Discussions
Compatibility with the ELM327...................................................66
Modifications for Low Power Standby Operation....................... 66
Microprocessor Interfaces..........................................................67
Example Applications.................................................................68
Misc
Error Messages and Alerts.........................................................72
Outline Diagrams....................................................................... 74
Ordering Information.................................................................. 74
Copyright and Disclaimer...........................................................74
Index.......................................................................................... 75
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ELM329DSB
Elm Electronics – Circuits for the Hobbyist
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