ELM327
Contents
Electrical Information
Using the ELM327
Pin Descriptions........................................................................... 3
Unused Pins.................................................................................5
Ordering Information.................................................................... 5
Absolute Maximum Ratings......................................................... 5
Electrical Characteristics..............................................................6
Overview...................................................................................... 7
Communicating with the ELM327................................................ 7
AT Commands............................................................................. 9
AT Command Summary...............................................................9
AT Command Descriptions........................................................ 11
Reading the Battery Voltage...................................................... 28
OBD Commands........................................................................29
Talking to the Vehicle.................................................................30
Interpreting Trouble Codes........................................................ 32
Resetting Trouble Codes........................................................... 33
Quick Guide for Reading Trouble Codes................................... 33
Bus Initiation...............................................................................34
Wakeup Messages.....................................................................34
Selecting Protocols.................................................................... 35
OBD Message Formats..............................................................36
Setting the Headers................................................................... 38
Monitoring the Bus..................................................................... 41
CAN Receive Filtering - the CRA Command............................. 42
Using the CAN Mask and Filter..................................................43
Multiline Responses...................................................................44
CAN Message Formats..............................................................46
Restoring Order..........................................................................47
Advanced Features
Altering Flow Control Messages................................................ 48
Using CAN Extended Addresses............................................... 49
SAE J1939 Messages................................................................50
Using J1939............................................................................... 52
The FMS Standard.....................................................................55
Programming Serial Numbers....................................................56
Saving a Data Byte.................................................................... 56
Programmable Parameters........................................................57
Programmable Parameter Summary......................................... 58
Using Higher RS232 Baud Rates...............................................63
Setting Timeouts - AT ST and AT AT Commands..................... 65
The Activity Monitor....................................................................66
Power Control............................................................................ 66
Design Examples
Misc.
Microprocessor Interfaces..........................................................70
Example Applications.................................................................71
Modifications for Low Power Standby Operation....................... 77
Error Messages and Alerts.........................................................78
Outline Diagrams....................................................................... 80
Copyright and Disclaimer...........................................................80
Index.......................................................................................... 81
2 of 82
ELM327DSI
Elm Electronics – Circuits for the Hobbyist
www.elmelectronics.com
ELM [ ELM ELECTRONICS ]
