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 |
PID |
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 |
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|
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 |
|
|
|
|
|
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 |