OBD-II PIDs

P-codes, or OBD-II PIDs On Board Diagnostics "Parameter IDs", are codes used to request data from a vehicle, used as a diagnostic tool. These codes are part of SAE standard J/1979, required to be implemented in all cars sold in North America since 1996.

Typically, an automotive technician will use PIDs with a scan tool connected to the vehicle's OBD-II connector.

• The technician enters the PID
• The scan tool sends it to the vehicle's bus (CAN, VPW, PWM, ISO, KWP. After 2008, CAN only)
• A device on the bus recognizes the PID as one it is responsible for, and reports the value for that PID to the bus
• The scan tool reads the response, and shows it to the technician

Modes

There are ten modes of operation described in the latest OBD-II standard SAE J1979. They are as follows (the 0x prefix indicates a hexadecimal radix):<br />0x01. Show current data<br />0x02. Show freeze frame data<br />0x03. Show stored Diagnostic Trouble Codes<br />0x04. Clear Diagnostic Trouble Codes and stored values<br />0x05. Test results, oxygen sensor monitoring (non CAN only)<br />0x06. Test results, other component/system monitoring (Test results, oxygen sensor monitoring for CAN only)<br />0x07. Show pending Diagnostic Trouble Codes (detected during current or last driving cycle)<br />0x08. Control operation of on-board component/system<br />0x09. Request vehicle information<br />0x0A. Permanent DTC's (Cleared DTC's)<br...
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