Code 11

IDLE FUEL TRIM POTENTIOMETER AND CIRCUIT - DTC 11

The ECM looks for the idle trim potentiometer signal voltage to be out of the normal operating range.

The idle trim potentiometer is used to adjust the ECM mapped injector pulse duration at idle. This adjustment enables the feedback system to operate around the same fueling baseline on any particular engine. The trim adjustment is set to obtain an oxygen sensor feedback value of 2-3 volts at idle. Typically, the idle trim voltage is between 1 and 4 volts. The potentiometer is located in the mass air flow sensor (MAFS) (air mass meter). The idle trim potentiometer is not used for 1993 ON model years.

Conditions Required For DTC 11 Flagging
- Throttle position: Closed (idle position)
- Idle trim potentiometer signal voltage to ECM: Greater than 4.0 volts
- Monitoring: Any time during ignition ON
- Response time: 8 milliseconds.

Limp Home Default
If DTC 11 is flagged, no correction is applied to the injector pulse duration at idle.

Possible Faults
- Open circuit wiring from the ECM to the MAFS
- Open circuit potentiometer within the MAFS
- Incorrect ECM part number
- Incorrect MAFS part number

Diagnostic Notes
1. The idle trim voltage can be monitored and intermittent faults captured using the PDU "Datalogger" function.






2. If DTC 12, 14, 16, 18, 19 and/or 39 are also flagged, suspect a defective sensor ground circuit to the ECM (BY wire) or defective ECM ground circuit to the front bulkhead ground stud.
3. The idle trim potentiometer has an adjustable range of approximately 10 to 1000 ohms, measured between pins 1 and 6 on the MAFS. The potentiometer can be adjusted after the anti-tamper plug is removed from the side of the MAFS.

Circuit Diagram

Idle Fuel Trim Potentiometer - Circuit Diagram:

Flow Chart: DTC 11

Flow Chart: DTC 11: