Evaporator Temperature Sensor Circuit

Evaporator Temperature Sensor:

WHEN MONITORED
With the ignition on.

SET CONDITION
The A/C Heater Control Module detects an abnormally high or low voltage on the Evaporator Temperature Sensor Signal circuit.

POSSIBLE CAUSES
- Evaporator temperature sensor signal circuit short to voltage
- Evaporator temperature sensor open
- Evaporator temperature sensor signal circuit open
- Evaporator temperature sensor ground open
- Evaporator temperature sensor signal circuit short to ground
- A/C heater control module

Diagnostic Test




1. READ EVAPORATOR TEMPERATURE SENSOR VOLTAGE WITH DRB III(R)

Turn the ignition on.
With the DRB III(R), read the Evaporator Temperature Sensor voltage.

Q: Does the DRB III(R) display EVAP TEMP: 5.0 VOLTS or greater?

YES: Go to 2
NO: Go to 6




2. MEASURE THE VOLTAGE OF THE EVAPORATOR TEMPERATURE SENSOR SIGNAL CIRCUIT

Turn the ignition off.
Disconnect the Evaporator Temperature Sensor harness connector.

NOTE: Check connector - Clean/repair as necessary.

Turn the ignition on.
Measure the voltage of the Evaporator Temperature Sensor Signal circuit at the Evaporator Temperature Sensor harness connector.

Q: Is the voltage above 5.5 volts?

YES: Repair the Evaporator Temperature Sensor Signal circuit for a short to voltage. Perform BODY VERIFICATION TEST. Body Verification Test
NO: Go to 3




3. READ EVAPORATOR TEMPERATURE SENSOR VOLTAGE WITH DRB III(R)

Turn the ignition off.
Connect a jumper wire between the Evaporator Temperature Sensor Signal circuit and the Sensor Ground circuit. Turn the ignition on. With the DRB III(R), read the Evaporator Temperature Sensor voltage.

Q: Does the DRB III(R) display EVAP TEMP: 4.5 VOLTS or greater?

YES: Go to 4
NO: Replace the Evaporator Temperature Sensor. Perform BODY VERIFICATION TEST. Body Verification Test




4. MEASURE THE RESISTANCE OF THE EVAPORATOR TEMPERATURE SENSOR SIGNAL CIRCUIT

Turn the ignition off.
Disconnect the A/C Heater Control Module harness connector.

NOTE: Check connector - Clean/repair as necessary. Measure the resistance of the Evaporator Temperature Sensor Signal circuit from the A/C Heater Control Module harness connector to the Evaporator Temperature Sensor harness connector.

Q: Is the resistance below 5.0 ohms?

YES: Go to 5
NO: Repair the Evaporator Temperature Sensor Signal circuit for an open. Perform BODY VERIFICATION TEST. Body Verification Test




5. MEASURE THE RESISTANCE OF THE SENSOR GROUND CIRCUIT

With the ignition off.
Measure the resistance of the Sensor Ground circuit from the A/C Heater Control Module harness connector to the Evaporator Temperature Sensor harness connector.

Q: Is the resistance below 5.0 ohms?

YES: Replace the A/C Heater Control Module. Perform BODY VERIFICATION TEST. Body Verification Test
NO: Repair the Sensor Ground circuit for an open. Perform BODY VERIFICATION TEST. Body Verification Test




6. READ EVAPORATOR TEMPERATURE SENSOR VOLTAGE WITH DRB III(R)

Turn the ignition off.
Disconnect the Evaporator Temperature Sensor harness connector.
NOTE: Check connector - Clean/repair as necessary.
Turn the ignition on.
With the DRB III(R), read the Evaporator Temperature Sensor voltage.

Q: Does the DRB III(R) display EVAP TEMP: 4.5 VOLTS or greater?

YES: Go to 7
NO: Go to 9




7. READ A/C HEATER CONTROL MODULE DTC'S WITH DRB III(R)

Turn the ignition off.
Reconnect the Evaporator Temperature Sensor connector.
Turn the ignition on.
With the DRB III(R), read A/C Heater Control Module DTC's.
Wait two minutes.
With the DRB III(R), read A/C Heater Control Module DTC's.

Q: Does the DRB III(R) display Evaporator Temperature Sensor Failure DTC?

YES: Replace the Evaporator Temperature Sensor. Perform BODY VERIFICATION TEST. Body Verification Test
NO: Go to 8




8. READ A/C HEATER CONTROL MODULE DTC'S WITH DRB III(R)

Ensure the Evaporator Temperature Sensor is connected at this time.
Start the engine.
Turn the A/C system on and run for at least five minutes (so water will form on the Evaporator Temperature Sensor).
With the DRB III(R), read A/C Heater Control Module DTC's.

Q: Does the DRB III(R) display an Evaporator Temperature Sensor Failure DTC?

YES: Replace the Evaporator Temperature Sensor. Perform BODY VERIFICATION TEST. Body Verification Test
NO: The condition that caused this DTC to set is currently not present. Inspect the related wiring harness for a possible intermittent condition. Perform BODY VERIFICATION TEST. Body Verification Test




9. MEASURE THE RESISTANCE BETWEEN GROUND AND THE EVAPORATOR TEMPERATURE SENSOR SIGNAL CIRCUIT

Turn the ignition off.
Disconnect the A/C Heater Control Module harness connector.
NOTE: Check connector - Clean/repair as necessary.
Measure the resistance between ground and the Evaporator Temperature Signal circuit.

Q: Is the resistance below 1000.0 ohms?

YES: Repair the Evaporator Temperature Sensor Signal circuit for a short to ground. Perform BODY VERIFICATION TEST. Body Verification Test
NO: Go to 10




10. MEASURE THE RESISTANCE FROM THE EVAPORATOR TEMPERATURE SENSOR SIGNAL CIRCUIT TO THE SENSOR GROUND CIRCUIT

With the ignition off.
Measure the resistance from the Evaporator Temperature Sensor Signal circuit to the Sensor Ground circuit at the Evaporator Temperature Sensor harness connector.

Q:Is the resistance below 1000.0 ohms?

YES: Repair the Evaporator Temperature Sensor Signal circuit for a short to the Sensor Ground circuit. Perform BODY VERIFICATION TEST. Body Verification Test
NO: Replace the A/C Heater Control Module. Perform BODY VERIFICATION TEST. Body Verification Test