1000 - 1999: 1230

1230-00 EVAPORATOR TEMPERATURE SENSOR CIRCUIT





When Monitored and Set Condition

- 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.





For a complete HVAC Circuit Diagram, HVAC Schematics and Diagrams.

Diagnostic Test

1. READ EVAPORATOR TEMPERATURE SENSOR VOLTAGE WITH scan tool
Turn the ignition on.
With the scan tool, read the Evaporator Temperature Sensor voltage.
Does the scan tool 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.
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 scan tool
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 scan tool, read the Evaporator Temperature Sensor voltage.
Does the scan tool display EVAP TEMP: 4.5 VOLTS or greater?

Yes

- Go to 4

No

- Replace the Evaporator Temperature Sensor. Removal.
- 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.
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.
Is the resistance below 5.0 ohms?

Yes

- Replace the A/C Heater Control Module. Removal.
- 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 scan tool
Turn the ignition off.
Disconnect the Evaporator Temperature Sensor harness connector.

NOTE: Check connector - Clean/repair as necessary.

Turn the ignition on.
With the scan tool, read the Evaporator Temperature Sensor voltage.
Does the scan tool 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 scan tool
Turn the ignition off.
Reconnect the Evaporator Temperature Sensor connector.
Turn the ignition on.
With the scan tool, read A/C Heater Control Module DTC's.
Wait two minutes.
With the scan tool, read A/C Heater Control Module DTC's.
Does the scan tool display Evaporator Temperature Sensor Failure DTC?

Yes

- Replace the Evaporator Temperature Sensor. Removal.
- Perform BODY VERIFICATION TEST. Body Verification Test

No

- Go to 8

8. READ A/C HEATER CONTROL MODULE DTC'S WITH scan tool
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 scan tool, read A/C Heater Control Module DTC's.
Does the scan tool display an Evaporator Temperature Sensor Failure DTC?

Yes

- Replace the Evaporator Temperature Sensor. Removal.
- 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.
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.
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. Removal
- Perform BODY VERIFICATION TEST. Body Verification Test