DTC 4-1-3

4-1-3 EGR TEMPERATURE SENSOR SIGNAL

Condition(s) for DTC
^ The ICM uses the EGR temperature sensor signal to determine whether or not an EGR flow is present. The DTC will be recorded if the signal from the sensor to the ICM is too high, too low or faulty (i.e. the signal changes although the ICM has not delivered a control signal to the vacuum controller).

Substitute value
^ None.

Fault source(s)
^ Signal too high:
- Signal lead short-circuited to supply.
- Open-circuit in signal lead or ground lead.
- Faulty EGR temperature sensor.
- Stray current in connector.

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

^ Faulty signal:
- Contact resistance and oxidation in connector.

Fault symptom(s)
^ None.

TESTING PROCEDURE





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: Permanent fault, faulty signal:
- Proceed to: PERMANENT FAULT, FAULTY SIGNAL 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.
If Status message is: Intermittent fault, faulty signal:
- Proceed to: INTERMITTENT FAULT, FAULTY SIGNAL Section below.

^ The fault counter indicates the number of starts during which the ICM has detected a fault free signal after the DTC has been recorded.

PERMANENT FAULT, SIGNAL TOO HIGH





Checking and cleaning sensor connector
^ DTC may be due to contact resistance in the connector.
^ Clean and treat sensor connector against oxidation.
^ Proceed to: Checking ground lead.





Checking ground lead
^ Switch OFF ignition.
^ Disconnect sensor.
^ Connect ohmmeter between sensor connector terminal 2 (ICM side) and ground.

Instrument should indicate approx. 0 Ohms.

If reading is correct:
- Check signal lead.
If instrument indicates 5 - 5O Ohms:
- Disconnect ground terminal 31/33 (under intake manifold on cylinder block).
- Clean and reconnect ground terminal.
If instrument Indicates over 50 Ohms:
- Check lead between ICM A16 and sensor connector terminal 2 for open-circuit.





Checking signal lead
^ Switch ON ignition.
^ Disconnect sensor.
^ Connect voltmeter across sensor connector terminals 1 and 2 (ICM side).

Instrument should indicate approx. 5 Volts.

If reading is correct:
- Check sensor.
If reading is above 5 Volts:
- Check lead between ICM A15 and sensor connector terminal 1 for short-circuit to supply.
When fault has been corrected:
- Check sensor.
If reading is approx. 0 Volts:
- Check lead between ICM A15 and sensor connector terminal 1 for open-circuit.





Checking sensor
^ Switch OFF ignition.
^ Disconnect sensor.





^ Connect ohmmeter between terminals 1 and 2 on sensor connector (sensor side).

Instrument should indicate approx. 200K Ohms at +20 °C (68 °F) (see chart).

If reading is correct:
- Check sensor signal.
If reading is incorrect:
- Try with new sensor.





Checking sensor signal
^ In certain cases, sensor may fail if signal lead is short-circuited to supply.
^ START engine.
^ Display DTC parameter list.
^ Read sensor signal value.

Value should be between 1.8 and 4.6 Volts depending on sensor temperature.

4.6 Volts at 0°C (32°F) and 1.8 Volts at 80°C (176°F).
Note that voltage falls with increasing temperature.

^ Disconnect yellow hose from EGR controller.
^ Connect vacuum gauge to hose at EGR valve.
^ Pump up vacuum.

Engine should idle unevenly.
In addition, voltage should fall as temperature rises.

If reading is correct:
- Sensor is intact.
- DTC is due to poor or loose connection in sensor connector.
If reading is incorrect:
- Try with new sensor.

PERMANENT FAULT, SIGNAL TOO LOW





Checking signal lead
^ Switch ON ignition.
^ Display DTC parameter list.
^ Read sensor signal.
^ Disconnect sensor connector.

Reading should alter to approx. 5 Volts.

If reading is correct:
- Try with new sensor.
If reading is incorrect:
- Check lead between ICM A5 and sensor connector terminal 1 for short-circuit to ground.

PERMANENT FAULT, FAULTY SIGNAL





Checking sensor signal
^ START engine.
^ Display DTC parameter list.
^ Read sensor signal value.

Value should be between 1.8 and 4.6 Volts depending on sensor temperature.

4.6 Volts at 0°C (32°F) and 1.8 Volts at 80°C (176°F).
Note that voltage falls with increasing temperature.

^ Disconnect yellow hose from EGR controller.





^ Connect vacuum gauge to hose at EGR valve.
^ Pump up vacuum.

Engine should idle unevenly.
In addition, voltage should fall as temperature rises.

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 ICM connectors for loose connections, and for contact resistance and oxidation.
^ Check lead between ICM A16 and sensor connector terminal 2 for intermittent open-circuit.
^ Check lead between ICM A15 and sensor connector terminal 1 for intermittent open-circuit, and for intermittent short-circuit to supply.

INTERMITTENT FAULT, SIGNAL TOO LOW





Checking wiring and connections
^ Check lead between ICM A5 and sensor connector terminal 1 for intermittent short-circuit to ground.

INTERMITTENT FAULT, FAULTY SIGNAL





Checking connections
^ Check sensor connector for intermittent contact resistance and oxidation.