OBD-II PIDs
From Wikipedia, the free encyclopedia
OBD-II PIDs On Board Diagnostics "Parameter IDs" are codes used to requests data from a vehicle, used as a diagnostic tool. The Society of Automotive Engineers (SAE) J2012 standard defines a number of generic "Diagnostic Trouble Codes" (DTCs).
Typically, a car mechanic will use PIDs with a scan tool connected to the vehicle's OBD-II connector.
- The mechanic enters the PID
- The scan tool sends to the vehicle's Controller Area Network (CAN) bus
- A device on the bus recognizes the PID as one it is responsible for, and reports the value for that PID to the CAN Bus
- The scan tool reads the response, and shows it to the mechanic
Contents |
[edit] Modes
There are nine modes of operation described in the OBD-II standard SAE J1979). They are:
- Show current data
- Show freeze frame data
- Show stored Diagnostic Trouble Codes
- Clear Diagnostic Trouble Codes and stored values
- Test results, oxygen sensor monitoring
- Test results, other component/system monitoring (e.g. Catalyst, EVAP)
- Show pending Diagnostic Trouble Codes (detected during current or last driving cycle)
- Control operation of on-board component/system
- Request vehicle information
Vehicle manufactures are not required to support all modes.
Each manufacturer may define additional modes above #9 (e.g.: Bank 22 for the Ford Escape) for other information (for example, the voltage of the Traction Battery in a HEV).
[edit] PIDs
The table below shows the standard OBD-II PIDs as defined by SAE J1979. The expected response for each PID is given, along with information on how to translate the response into meaningful data. Again, not all vehicles will support all PIDs and there can be manufacturer-defined custom PIDs that are not defined in the OBD-II standard.
Note that modes 1 and 2 are basically identical, except that Mode 1 provides current information, whereas Mode 2 provides a snapshot of the same data taken at the point when the last diagnostic trouble code was set. The exceptions are PID 01, which is only available in Mode 1, and PID 02, which is only available in Mode 2. If Mode 2 PID 02 returns zero, then there is no snapshot and all other Mode 2 data is meaningless.
| Mode (hex) |
PID (hex) |
Data bytes returned | Description | Min value | Max value | Units | Formula |
|---|---|---|---|---|---|---|---|
| 01 | 00 | 4 | PIDs supported | Bit encoded [A7..D0] == [PID 0x01..PID 0x20] | |||
| 01 | 01 | 4 | Number of trouble codes and I/M info | Bit encoded. See below. | |||
| 01 | 02 | 8 | Freeze DTC | ||||
| 01 | 03 | 2 | Fuel system status | Bit encoded. See below. | |||
| 01 | 04 | 1 | Calculated engine load value | 0 | 100 | % | A*100/255 |
| 01 | 05 | 1 | Engine coolant temperature | -40 | 215 | °C | A-40 |
| 01 | 06 | 1 | Short term fuel % trim—Bank 1 | -100 (Rich) | 99.22 (Lean) | % | 0.7812 * (A-128) |
| 01 | 07 | 1 | Long term fuel % trim—Bank 1 | -100 (Rich) | 99.22 (Lean) | % | 0.7812 * (A-128) |
| 01 | 08 | 1 | Short term fuel % trim—Bank 2 | -100 (Rich) | 99.22 (Lean) | % | 0.7812 * (A-128) |
| 01 | 09 | 1 | Long term fuel % trim—Bank 2 | -100 (Rich) | 99.22 (Lean) | % | 0.7812 * (A-128) |
| 01 | 0A | 1 | Fuel pressure | 0 | 765 | kPa (gauge) | A*3 |
| 01 | 0B | 1 | Intake manifold pressure | 0 | 255 | kPa (absolute) | A |
| 01 | 0C | 2 | Engine RPM | 0 | 16,383.75 | rpm | ((A*256)+B)/4 |
| 01 | 0D | 1 | Vehicle speed | 0 | 255 | km/h | A |
| 01 | 0E | 1 | Timing advance | -64 | 63.5 | ° relative to #1 cylinder | A/2 - 64 |
| 01 | 0F | 1 | Intake air temperature | -40 | 215 | °C | A-40 |
| 01 | 10 | 2 | MAF air flow rate | 0 | 655.35 | g/s | ((256*A)+B) / 100 |
| 01 | 11 | 1 | Throttle position | 0 | 100 | % | A*100/255 |
| 01 | 12 | 1 | Sec.(?) air status | Bit encoded. See below. | |||
| 01 | 13 | 1 | Oxygen sensors present | [A0..A3] == Bank 1, Sensors 1-4. [A4..A7] == Bank 2... | |||
| 01 | 14 | 2 | Bank 1, Sensor 1: Oxygen sensor voltage, Short term fuel trim |
0 0 |
1.275 99.2 |
Volts % |
A * 0.005 (B-128) * 0.7812 (if B==0xFF, sensor is not used in trim calc) |
| 01 | 15 | 2 | Bank 1, Sensor 2: Oxygen sensor voltage, Short term fuel trim |
0 0 |
1.275 99.2 |
Volts % |
A * 0.005 (B-128) * 0.7812 (if B==0xFF, sensor is not used in trim calc) |
| 01 | 16 | 2 | Bank 1, Sensor 3: Oxygen sensor voltage, Short term fuel trim |
0 0 |
1.275 99.2 |
Volts % |
A * 0.005 (B-128) * 0.7812 (if B==0xFF, sensor is not used in trim calc) |
| 01 | 17 | 2 | Bank 1, Sensor 4: Oxygen sensor voltage, Short term fuel trim |
0 0 |
1.275 99.2 |
Volts % |
A * 0.005 (B-128) * 0.7812 (if B==0xFF, sensor is not used in trim calc) |
| 01 | 18 | 2 | Bank 2, Sensor 1: Oxygen sensor voltage, Short term fuel trim |
0 0 |
1.275 99.2 |
Volts % |
A * 0.005 (B-128) * 0.7812 (if B==0xFF, sensor is not used in trim calc) |
| 01 | 19 | 2 | Bank 2, Sensor 2: Oxygen sensor voltage, Short term fuel trim |
0 0 |
1.275 99.2 |
Volts % |
A * 0.005 (B-128) * 0.7812 (if B==0xFF, sensor is not used in trim calc) |
| 01 | 1A | 2 | Bank 2, Sensor 3: Oxygen sensor voltage, Short term fuel trim |
0 0 |
1.275 99.2 |
Volts % |
A * 0.005 (B-128) * 0.7812 (if B==0xFF, sensor is not used in trim calc) |
| 01 | 1B | 2 | Bank 2, Sensor 4: Oxygen sensor voltage, Short term fuel trim |
0 0 |
1.275 99.2 |
Volts % |
A * 0.005 (B-128) * 0.7812 (if B==0xFF, sensor is not used in trim calc) |
| 01 | 1C | 1 | OBD standards this vehicle conforms to | Bit encoded. See below. | |||
| 01 | 1D | 1 | Oxygen sensors present | Similar to PID 13, but [A0..A7] == [B1S1, B1S2, B2S1, B2S2, B3S1, B3S2, B4S1, B4S2] | |||
| 01 | 1E | 1 | Auxiliary input status | A0 == Power Take Off (PTO) status (1 == active) [A1..A7] not used |
|||
| 01 | 1F | 2 | Run time since engine start | 0 | 65,535 | seconds | (A*256)+B |
| 01 | 20 | 4 | PIDs supported 21-40 | Bit encoded [A7..D0] == [PID 0x21..PID 0x40] | |||
| 01 | 21 | 2 | Distance traveled with malfunction indicator lamp (MIL) on | 0 | 65,535 | km | (A*256)+B |
| 01 | 22 | 2 | Fuel Rail Pressure (relative to manifold vacuum) | 0 | 5177.265 | kPa | ((A*256)+B) * 0.079 |
| 01 | 23 | 2 | Fuel Rail Pressure (diesel) | 0 | 655350 | kPa (gauge) | ((A*256)+B) * 10 |
| 01 | 24 | 4 | O2S1_WR_lambda(1): Equivalence Ratio Voltage |
0 0 |
2 8 |
N/A V |
((A*256)+B)*0.0000305 ((C*256)+D)*0.000122 |
| 01 | 25 | 4 | O2S2_WR_lambda(1): Equivalence Ratio Voltage |
0 0 |
2 8 |
N/A V |
((A*256)+B)*0.0000305 ((C*256)+D)*0.000122 |
| 01 | 26 | 4 | O2S3_WR_lambda(1): Equivalence Ratio Voltage |
0 0 |
2 8 |
N/A V |
((A*256)+B)*0.0000305 ((C*256)+D)*0.000122 |
| 01 | 27 | 4 | O2S4_WR_lambda(1): Equivalence Ratio Voltage |
0 0 |
2 8 |
N/A V |
((A*256)+B)*0.0000305 ((C*256)+D)*0.000122 |
| 01 | 28 | 4 | O2S5_WR_lambda(1): Equivalence Ratio Voltage |
0 0 |
2 8 |
N/A V |
((A*256)+B)*0.0000305 ((C*256)+D)*0.000122 |
| 01 | 29 | 4 | O2S6_WR_lambda(1): Equivalence Ratio Voltage |
0 0 |
2 8 |
N/A V |
((A*256)+B)*0.0000305 ((C*256)+D)*0.000122 |
| 01 | 2A | 4 | O2S7_WR_lambda(1): Equivalence Ratio Voltage |
0 0 |
2 8 |
N/A V |
((A*256)+B)*0.0000305 ((C*256)+D)*0.000122 |
| 01 | 2B | 4 | O2S8_WR_lambda(1): Equivalence Ratio Voltage |
0 0 |
2 8 |
N/A V |
((A*256)+B)*0.0000305 ((C*256)+D)*0.000122 |
| 01 | 2C | 1 | Commanded EGR | 0 | 100 | % | 100*A/255 |
| 01 | 2D | 1 | EGR Error | -100 | 99.22 | % | A*0.78125 - 100 |
| 01 | 2E | 1 | Commanded evaporative purge | 0 | 100 | % | 100*A/255 |
| 01 | 2F | 1 | Fuel Level Input | 0 | 100 | % | 100*A/255 |
| 01 | 30 | 1 | # of warm-ups since codes cleared | 0 | 255 | N/A | A |
| 01 | 31 | 2 | Distance traveled since codes cleared | 0 | 65,535 | km | (A*256)+B |
| 01 | 32 | 2 | Evap. System Vapor Pressure | -8,192 | 8,192 | Pa | ((A*256)+B)/4 - 8,192 |
| 01 | 33 | 1 | Barometric pressure | 0 | 255 | kPa (Absolute) | A |
| 01 | 34 | 4 | O2S1_WR_lambda(1): Equivalence Ratio Current |
0 -128 |
2 128 |
N/A mA |
((A*256)+B)*0.0000305 ((C*256)+D)*0.00391 - 128 |
| 01 | 35 | 4 | O2S2_WR_lambda(1): Equivalence Ratio Current |
0 -128 |
2 128 |
N/A mA |
((A*256)+B)*0.0000305 ((C*256)+D)*0.00391 - 128 |
| 01 | 36 | 4 | O2S3_WR_lambda(1): Equivalence Ratio Current |
0 -128 |
2 128 |
N/A mA |
((A*256)+B)*0.0000305 ((C*256)+D)*0.00391 - 128 |
| 01 | 37 | 4 | O2S4_WR_lambda(1): Equivalence Ratio Current |
0 -128 |
2 128 |
N/A mA |
((A*256)+B)*0.0000305 ((C*256)+D)*0.00391 - 128 |
| 01 | 38 | 4 | O2S5_WR_lambda(1): Equivalence Ratio Current |
0 -128 |
2 128 |
N/A mA |
((A*256)+B)*0.0000305 ((C*256)+D)*0.00391 - 128 |
| 01 | 39 | 4 | O2S6_WR_lambda(1): Equivalence Ratio Current |
0 -128 |
2 128 |
N/A mA |
((A*256)+B)*0.0000305 ((C*256)+D)*0.00391 - 128 |
| 01 | 3A | 4 | O2S7_WR_lambda(1): Equivalence Ratio Current |
0 -128 |
2 128 |
N/A mA |
((A*256)+B)*0.0000305 ((C*256)+D)*0.00391 - 128 |
| 01 | 3B | 4 | O2S8_WR_lambda(1): Equivalence Ratio Current |
0 -128 |
2 128 |
N/A mA |
((A*256)+B)*0.0000305 ((C*256)+D)*0.00391 - 128 |
| 01 | 3C | 2 | Catalyst Temperature Bank 1, Sensor 1 |
-40 | 6,513.5 | °C | ((A*256)+B)/10 -40 |
| 01 | 3D | 2 | Catalyst Temperature Bank 2, Sensor 1 |
-40 | 6,513.5 | °C | ((A*256)+B)/10 -40 |
| 01 | 3E | 2 | Catalyst Temperature Bank 1, Sensor 2 |
-40 | 6,513.5 | °C | ((A*256)+B)/10 -40 |
| 01 | 3F | 2 | Catalyst Temperature Bank 2, Sensor 2 |
-40 | 6,513.5 | °C | ((A*256)+B)/10 -40 |
| 01 | 40 | 4 | PIDs supported 41-60 (?) | Bit encoded [A7..D0] == [PID 0x41..PID 0x60] (?) | |||
| 01 | 41 | ? | Monitor status this drive cycle | ? | ? | ? | ? |
| 01 | 42 | 2 | Control module voltage | 0 | 65.535 | V | ((A*256)+B)/1000 |
| 01 | 43 | 2 | Absolute load value | 0 | 25696 | % | ((A*256)+B)*100/255 |
| 01 | 44 | 2 | Command equivalence ratio | 0 | 2 | N/A | ((A*256)+B)*0.0000305 |
| 01 | 45 | 1 | Relative throttle position | 0 | 100 | % | A*100/255 |
| 01 | 46 | 1 | Ambient air temperature | -40 | 215 | °C | A-40 |
| 01 | 47 | 1 | Absolute throttle position B | 0 | 100 | % | A*100/255 |
| 01 | 48 | 1 | Absolute throttle position C | 0 | 100 | % | A*100/255 |
| 01 | 49 | 1 | Accelerator pedal position D | 0 | 100 | % | A*100/255 |
| 01 | 4A | 1 | Accelerator pedal position E | 0 | 100 | % | A*100/255 |
| 01 | 4B | 1 | Accelerator pedal position F | 0 | 100 | % | A*100/255 |
| 01 | 4C | 1 | Commanded throttle actuator | 0 | 100 | % | A*100/255 |
| 01 | 4D | 2 | Time run with MIL on | 0 | 65,535 | minutes | (A*256)+B |
| 01 | 4E | 2 | Time since trouble codes cleared | 0 | 65,535 | minutes | (A*256)+B |
| 01 | C3 | ? | ? | ? | ? | ? | Returns numerous data, including Drive Condition ID and Engine Speed* |
| 01 | C4 | ? | ? | ? | ? | ? | B5 is Engine Idle Request B6 is Engine Stop Request* |
| 02 | 02 | 2 | Freeze frame trouble code | BCD encoded, see below. | |||
| 03 | N/A | n*6 | Request trouble codes | 3 codes per message frame, BCD encoded. See below. | |||
| 04 | N/A | 0 | Clear trouble codes / Malfunction indicator lamp (MIL) / Check engine light | Clears all stored trouble codes and turns the MIL off. | |||
| 09 | 02 | 5x5 | Vehicle identification number (VIN) | Returns 5 lines, A is line ordering flag, B-E ASCII coded VIN digits. |
In the formula column, letters A, B, C, etc. represent the decimal equivalent of the first, second, third, etc. bytes of data. Where a (?) appears, contradictory or incomplete information was available. Someone with a copy of the 2006 SAE HS-3000 should fact-check these.
[edit] Bitwise encoded PIDs
Some of the PIDs in the above table cannot be explained with a simple formula. A more elaborate explanation of these data is provided here:
Mode 1 PID 01: A request for this PID returns 4 bytes of data. The first byte contains two pieces of information. Bit A7 (the seventh bit of byte A, the first byte) indicates whether or not the MIL (check engine light) is illuminated. Bits A0 through A6 represent the number of diagnostic trouble codes currently flagged in the ECU. The second, third, and fourth bytes give information about the availability and completeness of certain on-board tests. Note that test availability signified by set (1) bit; completeness signified by reset (0) bit:
Test available Test incomplete
Misfire B0 B4
Fuel System B1 B5
Components B2 B6
Reserved B3 B7
Catalyst C0 D0
Heated Catalyst C1 D1
Evaporative System C2 D2
Secondary Air System C3 D3
A/C Refrigerant C4 D4
Oxygen Sensor C5 D5
Oxygen Sensor Heater C6 D6
EGR System C7 D7
Mode 1 PID 03: A request for this PID returns 2 bytes of data. The first byte describes fuel system #1. Only one bit should ever be set.
A0 Open loop due to insufficient engine temperature A1 Closed loop, using oxygen sensor feedback to determine fuel mix A2 Open loop due to engine load A3 Open loop due to system failure A4 Closed loop, using at least one oxygen sensor but there is a fault in the feedback system A5-A7 Always zero
The second byte describes fuel system #2 (if it exists) and is encoded identically to the first byte.
Mode 1 PID 12: A request for this PID returns a single byte of data which describes the secondary air status. Only one bit should ever be set.
A0 Upstream of catalytic converter A1 Downstream of catalytic converter A2 From the outside atmosphere or off A3-A7 Always zero
Mode 1 PID 1C: A request for this PID returns a single byte of data which describes which OBD standards this ECU was designed to comply with. The hexadecimal and binary representations of the data byte are shown below next to what it implies:
0x01 00000001b OBD-II as defined by the CARB 0x02 00000010b OBD as defined by the EPA 0x03 00000011b OBD ''and'' OBD-II 0x04 00000100b OBD-I 0x05 00000101b Not meant to comply with any OBD standard 0x06 00000110b EOBD
Mode 3: (no PID required) A request for this mode returns information about the DTCs that have been set. The response will be an integer number of packets each containing 6 data bytes. Each trouble code requires 2 bytes to describe, so the number of packets returned will be the number of codes divided by three, rounded up. A trouble code can be decoded from each pair of data bytes. The first character in the trouble code is determined by the first two bits in the first byte:
A7 A6 First DTC character -- -- ------------------- 0 0 P - Powertrain 0 1 C - Chassis 1 0 B - Body 1 1 U - Network
As of September 2005, only P and U generic DTCs are standardized.
The second character in the DTC is a number defined by
A5 A4 Second DTC character -- -- -------------------- 0 0 0 0 1 1 1 0 2 1 1 3
The third character in the DTC is a number defined by
A3 A2 A1 A0 Third DTC character -- -- -- -- ------------------- 0 0 0 0 0 0 0 0 1 1 0 0 1 0 2 0 0 1 1 3 0 1 0 0 4 0 1 0 1 5 0 1 1 0 6 0 1 1 1 7 1 0 0 0 8 1 0 0 1 9
The fourth and fifth characters are defined in the same way as the third, but using bits B7..B4 and B3..B0. The resulting five-character code should look something like "U0158" and can be looked up in a table of OBD-II DTCs.
[edit] CAN Bus format
The PID query and response occurs on the vehicle's CAN Bus, using 3 particular CAN ids.
[edit] Query
The PID query is sent to the vehicle on the CAN bus at ID 7DFh, using 8 data bytes. The bytes are:
| Byte -> | _ 0 _ | _ 1 _ | _ 2 _ | _ 3 _ | _ 4 _ | _ 5 _ | _ 6 _ | _ 7 _ |
|---|---|---|---|---|---|---|---|---|
| SAE Standard | Number of additional data bytes: 2 |
Mode 01 = show current data; 02 = freeze frame; etc. |
PID code (e.g.: 05 = Engine coolant temperature) |
not used (may be 55h) |
||||
| Vehicle specific | Number of additional data bytes: 3 |
Custom mode: (e.g.:22 = enhanced data) | PID code (e.g.: 4980h) |
not used (may be 00h or 55h) |
||||
[edit] Response
The vehicle responds to the PID query on the CAN bus with two messages, at IDs 7E8h and 7E9h. For standrad (SAE) messages, the two messages are identical. For vehicle specific messages, they differ. Even though the number of bytes in the returned value is variable, the message uses 8 data bytes regardless. The bytes are:
| Byte -> | _ 0 _ | _ 1 _ | _ 2 _ | _ 3 _ | _ 4 _ | _ 5 _ | _ 6 _ | _ 7 _ |
|---|---|---|---|---|---|---|---|---|
| SAE Standard 7E8h and 7E9h or 7EAh |
Number of additional data bytes: 3 to 6 |
Custom mode Same as query, except that bit 6 is set. So: 41 = show current data; 42 = freeze frame; etc. |
PID code (e.g.: 05 = Engine coolant temperature) |
value of the specified parameter, byte 0 | value, byte 1 (optional) | value, byte 2 (optional) | value, byte 3 (optional) | not used (may be 00h or 55h) |
| Vehicle specific 7E8h |
Number of additional data bytes: 3 to 6 |
Custom mode: same as query, except that bits 5 and 6 are set.(e.g.:62 = response to mode 22 request) | PID code (e.g.: 4980h) |
value of the specified parameter, byte 0 | value, byte 1 (optional) | value, byte 2 (optional) | value, byte 3 (optional) | |
| Vehicle specific 7E9h |
Number of additional data bytes: 3 |
7Fh | Custom mode: (e.g.:22 = enhanced diagnostic data) | 31h | not used (may be 00h) |
|||
[edit] External links
- OBD-Codes.com, detailed troubleshooting information on OBD-II codes
