OBD II J1979
Onboard Diagnostics 2 or OBD2 is supported by the ECU using the SAE J1979 standard. The ECU supports the following service requests:
- Show current data
- Mil Status
- Show stored Diagnostic Trouble Codes (DTCs)
- Clear Diagnostic Trouble Codes (DTC) and stored values
- Request vehicle information
OBD II Service Mode 01 - Show Current Data
The ECU supports the following PIDs when the “Show Current Data” serviced is requested.
| PID (hex) | PID (Dec) | Data bytes returned | Description | Min value | Max value | Units | Notes |
|---|---|---|---|---|---|---|---|
| 01 | 1 | 4 | Monitor status since DTCs cleared. (Includes malfunction indicator lamp (MIL) status and number of DTCs.) | ||||
| 03 | 3 | 2 | Fuel system status | Only displayed when Closed Loop Fuel enabled. See Below | |||
| 04 | 4 | 1 | Calculated engine load | 0 | 100 | % | |
| 05 | 5 | 1 | Engine coolant temperature | -40 | 215 | °C | |
| 06 | 6 | 1 | Short term fuel trim—Bank 1 | -100 | 99.2 | % | Only displayed when Closed Loop Fuel enabled |
| 07 | 7 | 1 | Long term fuel trim—Bank 1 | ||||
| 08 | 8 | 1 | Short term fuel trim—Bank 2 | ||||
| 09 | 9 | 1 | Long term fuel trim—Bank 2 | ||||
| 0A | 10 | 1 | Fuel pressure (gauge pressure) | 0 | 765 | kPa | Only displayed when Fuel Pressure input enabled |
| 0B | 11 | 1 | Manifold absolute pressure | 0 | 255 | kPa | |
| 0C | 12 | 2 | Engine RPM | 0 | 16,383 | rpm | |
| 0D | 13 | 1 | Vehicle speed | 0 | 255 | km/h | |
| 0E | 14 | 1 | Timing advance | -64 | 63.5 | ° before TDC | |
| 0F | 15 | 1 | Inlet Air Temperature | -40 | 215 | °C | |
| 10 | 16 | 1 | Final Mass Flow Rate | 0 | 655.35 | g/s | Note. This is Final flow rate, not MAF flow rate |
| 11 | 17 | 1 | Throttle Position/Servo Main (for DBW Application) | 0 | 100 | % | |
| 14 | 20 | 1 | Narrow Band Oxygen Sensor 1 | 0 | 1.275 | V | Only displayed when Narrow-band input enabled |
| 15 | 21 | 1 | Narrow Band Oxygen Sensor 2 | 0 | 1.275 | V | Only displayed when Narrow-band input enabled |
| 1C | 28 | 1 | OBD standards this vehicle conforms to | See Below | |||
| 1F | 31 | 2 | Run time since engine start | 0 | 65535 | seconds |
Supplementary Information
PID 0x03 - Fuel System Closed Loop Status
| CAN Value | Suffix | Description |
|---|---|---|
| 1 | OPEN | Open loop due to insufficient engine temperature |
| 2 | CLSD | Closed loop, using oxygen sensor feedback to determine fuel mix |
| 4 | OPEN1 | Open loop due to lockout condition or OFF (fuel cut due to deceleration, limiting, post start etc) |
| 8 | OPEN 2 | Open loop due to system failure |
| 16 | CLSD1 | Closed loop, using at least one oxygen sensor but there is a fault in the feedback system |
PID 0x04 - Calculated Engine Load
There are 2 types of load defined by the SAE J1979, one is Calculated engine load the other Absolute engine load. The Calculated Load is referenced to engine speed, so its the %Engine Load at that RPM.
As defined by ODB II regulations Calculated load = (Current airflow / peak airflow @sea level) x (Baro @sea level / Baro) x 100%
PID 0x1C - OBD standards this vehicle conforms to
A request for this PID returns a single byte of data which describes which OBD standards this ECU was designed to comply with. Emtron replies with a value of 6
| Value | Description |
|---|---|
| 1 | OBD-II as defined by the CARB |
| 2 | OBD as defined by the EPA |
| 3 | OBD and OBD-II |
| 4 | OBD-I |
| 5 | Not OBD compliant |
| 6 | EOBD (Europe) |
| 7 | EOBD and OBD-II |
| 8 | EOBD and OBD |
| 9 | EOBD, OBD and OBD II |
| 10 | JOBD (Japan) |
| 11 | JOBD and OBD II |
| 12 | JOBD and EOBD |
| 13 | JOBD, EOBD, and OBD II |
| 14 | Reserved |
| 15 | Reserved |
| 16 | Reserved |