Ignition System

4-1-1 THROTTLE POSITION POTENTIOMETER SIGNAL

Condition(s) for DTC
^ The Throttle Position (TP) Potentiometer is used to record the throttle position from Closed Throttle Position to Wide Open Throttle. The signal is also used to switch out the A/C system at full load for a maximum of 15 seconds. It the sensor signal remains constant below 0.10 Volt or above 4.85 Volts for a number of successive ignitions, the ICM interprets the condition as a fault and the DTC is recorded.

Substitute value
^ A substitute value equivalent to an opening of approx. 68° is assumed.

Fault source(s)
^ Signal too high:
- Open-circuit in signal lead.
- Signal lead short-circuited to supply.
- Contact resistance in terminals.

^ Signal too low:
- Signal lead short-circuited to ground.

Fault symptom(s)
^ Impaired performance.

TESTING PROCEDURES





Other DTCs
^ Read other DTCs.

If MFI DTC 1-2-3 is recorded:
- Proceed to: Testing By Trouble Code / Fuel Injection System / DTC 1-2-3 Engine Coolant Temperature Sensor Signal.
If MFI DTC 2-2-3 is recorded:
- Proceed to: Testing By Trouble Code / Fuel Injection System / DTC 2-2-3 Idle Air Control Valve Signal.
If MFI DTC 4-1-1 is recorded:
- Proceed to: Testing By Trouble Code / Fuel Injection System / DTC 4-1-1 Throttle Position Potentiometer Signal.
If none of above DTCs is recorded:
- Check Status message.





Status message
^ Check current Status Message.

If Status message is: Permanent fault, signal too high:
- Proceed to: PERMANENT FAULT, SIGNAL TOO HIGH Section below.
If Status message is: Permanent fault, signal too low:
- Proceed to: PERMANENT FAULT, SIGNAL TOO LOW Section below.
If Status message is: Intermittent fault, signal too high:
- Proceed to: INTERMITTENT FAULT, SIGNAL TOO HIGH Section below.
If Status message is: Intermittent fault, signal too low:
- Proceed to: INTERMITTENT FAULT, SIGNAL TOO LOW Section below.

PERMANENT FAULT: SIGNAL TOO HIGH





Checking signal
^ Switch OFF ignition.
^ Connect test box to Ignition system and check ground terminals.





^ Switch ON ignition.
^ Connect voltmeter across #50 (DI B20) and #20 (DI A20) on test box.

Instrument should indicate approx. 0.5 Volts at Closed Throttle Position and approx. 4.2 Volts at Wide Open Throttle.

If reading is correct:
- Check ICM connector.
If instrument Indicates 0 Volts:
- Check MFI module connector.
If Instrument indicates battery voltage:
- Check lead between ICM B20 and MFI B20 for short-circuit to supply.
- On automatics, also check lead connected to TCM B20 for short-circuit to supply.





Checking ICM connector
^ Switch OFF ignition.
^ Disconnect test box.
^ Check ICM connector for contact resistance and oxidation.
^ Plug ICM into connector.
^ Switch ON ignition.





^ Display predefined list 14.

Throttle angle should be 10° - 14° at Closed Throttle Position and 90° - 100° at Wide Open Throttle.

If sensor signal is correct:
- DTC is due to poor contact in ICM connector.
If sensor signal is incorrect:
- Try with new ICM.





Checking MFI module connector
^ Switch OFF ignition.
^ Disconnect test box.
^ Plug ICM into connector.





^ Connect test box to MFI system and check ground terminals.
^ Plug MFI module into connector.
^ Switch ON ignition.
^ Connect voltmeter across #50 (MFI B20) and #20 (MFI A20) on test box.
^ Display predefined list 14.

Instrument should indicate approx. 0.5 Volts and throttle angle should be 10° - 14° at Closed Throttle Position.

If reading and throttle angle are correct:
- DTC is due to poor contact in MFI module connector.
- Check connector for contact resistance and oxidation.
If reading is correct but throttle angle is incorrect:
- Check lead between ICM B20 and MFI B20 for open-circuit.
If reading and throttle angle are both incorrect:
- Try with new MFI module.

PERMANENT FAULT, SIGNAL TOO LOW





Checking signal
^ Switch OFF ignition.
^ Connect test box to DI system and check ground terminals.





^ Switch ON ignition.
^ Connect voltmeter across #50 (DI B20) and #20 (DI A20) on test box.

Instrument should indicate approx. 0.5 Volts at Closed Throttle Position and approx. 4.2 Volts at Wide Open Throttle.

If reading is correct:
- Check control module connectors.
If reading is incorrect:
- Check signal lead.

Checking control module connectors
^ Switch OFF ignition.
^ Disconnect test box.
^ Plug ICM into connector.
^ Disconnect MFI module.
^ Switch ON ignition.





^ Display predefined list 14.

Throttle angle should be over 100°.

If reading is correct:
- DTC is due to poor contact in control module connectors.
- Check connectors for contact resistance and oxidation.
If reading is incorrect:
- Try with new ICM.





Checking signal lead
^ Switch OFF ignition.
^ Disconnect test box.
^ Plug ICM into connector.
^ Disconnect MFI module.
^ Switch ON ignition.
^ Display predefined list 14.

Throttle angle should be over 100°.

If reading is correct:
- Try with new MFI module.
If reading is incorrect:
- Check lead between ICM 20 and MFl 20 for short-circuit to ground.
- On automatics, also check lead connected to TCM B20 for short-circuit to ground.





INTERMITTENT FAULT, SIGNAL TOO HIGH

Checking wiring and connections
^ Check ICM B20 and MFI B20 for loose connections, and for contact resistance and oxidation.
^ Check lead between ICM B20 and MFI B20 for intermittent open-circuit and for intermittent short-circuit to supply.
^ On automatics, also check lead connected to TCM B20 for short-circuit to supply.





INTERMITTENT FAULT, SIGNAL TOO LOW

Checking wiring and connections
^ Check lead between ICM 20 and MFI 20 for intermittent short-circuit to ground.
^ On automatics, also check lead connected to TCM B20 for intermittent short-circuit to ground.