Fuel Injection System

4-1-1 THROTTLE POSITION POTENTIOMETER SIGNAL

Condition(s) for DTC
^ If the Throttle Position (TP) Potentiometer signal remains steady below 0.25 Volts or exceeds 4.75 Volts, the MFI module will interpret the condition as a fault and the DTC will be recorded.

Substitute value
^ The system will assume a substitute value equivalent to a throttle opening of approx. 15°.

Fault source(s)
^ Signal too high:
- Open-circuit in signal or ground lead.
- Ground lead short-circuited to supply.
- Contact resistance in connections.
- Faulty TP potentiometer.

^ Signal too low:
- Signal lead short-circuited to ground.
- Open-circuit in supply lead.
- Contact resistance in connections.
- Faulty sensor.

Fault symptom(s)
^ Incorrect idling speed.
^ Impaired full-load acceleration when A/C is not switched out.

TESTING PROCEDURE





Other DTCs
^ Read other DTCs.

If MFI DTC 1-2-3 is recorded:
- Check A14 on MFI module (common to TP and ECT sensors) for contact resistance and oxidation and for open-circuit.
If MFl DTC 1-2-3 is not 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 ground lead
^ Switch OFF ignition.
^ Disconnect TP potentiometer.
^ Wait approx. 30 seconds.
^ Connect ohmmeter between TP potentiometer connector terminal 1 and ground.

Instrument should indicate approx. 0 Ohms.

If reading is correct:
- Check signal lead.
If reading is incorrect:
- Check lead between TP potentiometer connector terminal 1 and MFI module A14 for open-circuit.





Checking signal lead
^ Switch ON ignition.
^ Disconnect TP potentiometer.
^ Connect voltmeter between TP potentiometer connector terminal 3 and ground.

Instrument should indicate approx. 5 Volts.

If reading is correct:
- Check sensor signal.
If instrument indicates approx. 0 Volts:
- Check lead between sensor connector terminal 3 and MFI module A1 for open-circuit.
If instrument indicates over 5 Volts:
- Check lead between sensor connector terminal 3 and MFI module A1 for short-circuit to supply.
When fault has been corrected:
- Check sensor signal.





Checking TP potentiometer signal
^ Connect sensor (if disconnected).
^ START engine.
^ Display DTC parameter list.
^ Read value of sensor signal.

Value should be approx. 0.5 Volts at Closed Throttle Position (CTP) (idling) and increase to approx. 4.2 Volts at Wide Open Throttle (WOT).

If reading is correct:
- DTC is due to poor connection in sensor connector. Check connector for contact resistance and oxidation.
If reading is incorrect:
- Try with new sensor.





Checking TP potentiometer
^ The sensor may fail if the signal lead is short-circuited to the supply. Check signal as follows:
^ Connect sensor (if disconnected).
^ START engine and allow to idle.
^ Erase DTC.

If MFI DTC 4-1-1 is recorded:
- Try with new sensor (if sensor is faulty, DTC will be recorded within 20 seconds).

PERMANENT FAULT, SIGNAL TOO LOW





Checking supply lead
^ Switch ON ignition.
^ Disconnect sensor.
^ Connect voltmeter across sensor connector terminals 1 and 2.

Instrument should indicate approx. 5 Volts.

If reading is correct:
- Check signal lead.
If instrument indicates approx. 0 Volts:
- Check lead between sensor connector terminal 2 and MFI module A2 for open-circuit.





Checking signal lead
^ Switch ON ignition.
^ Disconnect sensor.
^ Connect voltmeter across sensor contact terminals 1 and 3.

Instrument should indicate approx. 5 Volts.

If reading is correct:
- Check sensor signal.
If Instrument indicates approx. 0 Volts:
- Check lead between sensor connector terminal 3 and MFI module A1 for short-circuit to ground.





Checking TP potentiometer signal
^ Connect sensor (if disconnected).
^ START engine.
^ Display DTC parameter list.
^ Read value of sensor signal.

Value should be approx. 0.5 Volts at CTP (idling) and increase to approx. 4.2 Volts at WOT.

If reading is correct:
- DTC is due to poor connection in sensor connector. Check connector for contact resistance and oxidation.
If reading is incorrect:
- Try with new sensor.

INTERMITTENT FAULT, SIGNAL TOO HIGH





Checking wiring and connections
^ Check sensor and control module connectors for loose connections and for contact resistance and oxidation.
^ Check lead between sensor connector terminal 3 and MFI module A1 for intermittent open-circuit and for intermittent short-circuit to supply.
^ Check lead between sensor connector terminal 1 and MFI module A14 for intermittent open-circuit.

INTERMITTENT FAULT, SIGNAL TOO LOW





Checking wiring and connections
^ Check lead between sensor connector terminal 3 and MFI module A1 for intermittent short-circuit to ground.
^ Check lead between sensor connector terminal 2 and MFI module A2 for intermittent open-circuit.