0155

0155-THERMOSTAT CONTROL CIRCUIT/OPEN





For a complete wiring diagram Consult Diagrams/Electrical

- When Monitored:
With the engine running.

- Set Condition:
The PCM detects an open or shorted condition in the Thermostat control circuit.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.Initial Inspection and Diagnostic Overview

Diagnostic Test

1. DTC IS ACTIVE
Turn the ignition on.
With the scan tool, read DTCs.
Record all DTC and applicable Freeze Frame information.
With the scan tool, clear DTCs.
Cycle the ignition off for at least one minute.
Start the engine and allow it to reach operating temperature. If the engine will not start, crank the engine over for at least 10 seconds.

WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose fitting clothing. Failure to follow these instructions can result in personal or fatal injury.

With the scan tool, read DTCs.
Does this DTC reset?

Yes

- Go to 2

No

- Refer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure.Checking for an Intermittent DTC

2. THERMOSTAT WIRING AND CONNECTOR INSPECTION
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Thermostat and the Powertrain Control Module (PCM).
Look for any chafed, pierced, pinched, or partially broken wires.
Look for broken, bent, pushed out or corroded terminals.
Search for any Technical Service Bulletins that may apply.
Were any problems found?

Yes

- Repair as necessary.
- Perform the PCM Verification Test.Powertrain Verification Test

No

- Go to 3

3. FUSED MAIN RELAY OUTPUT CIRCUIT OPEN OR HIGH RESISTANCE




Turn the ignition off.
Disconnect the Thermostat harness connector.
Turn the ignition on.
Using a 12 volt test light connected to ground, check the Fused Main Relay Output circuit in the Thermostat harness connector.

NOTE: The test light should be illuminated and bright. Compare the brightness to that of a direct connection to the battery.

Is the test light illuminated and bright?

Yes

- Go to 4

No

- Repair the Fused Main Relay Output circuit for an open circuit or high resistance.
- Perform the PCM Verification Test.Powertrain Verification Test

4. THERMOSTAT CONTROL CIRCUIT OPEN OR HIGH RESISTANCE




Turn the ignition off.
Disconnect the Powertrain Control Module (PCM) harness connector.
Measure the resistance of the Thermostat Control circuit between the Thermostat harness connector and the Powertrain Control Module (PCM) harness connector.
Is the resistance below 5.0 ohms?

Yes

- Go to 5

No

- Repair the Thermostat Control circuit for an open circuit or high resistance.
- Perform the PCM Verification Test.Powertrain Verification Test

5. THERMOSTAT
Turn the ignition off.
Connect the Powertrain Control Module (PCM) harness connector.
Replace the Thermostat.
Turn the ignition on.
With the scan tool, clear DTCs.
Cycle the ignition off for at least one minute.
Start the engine and allow it to reach operating temperature.

WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose fitting clothing. Failure to follow these instructions can result in personal or fatal injury.

With the scan tool, read DTCs.
Does this DTC reset?

Yes

- Go to 6

No

- Test Complete.
- Perform the PCM Verification Test.Powertrain Verification Test

6. POWERTRAIN CONTROL MODULE (PCM)
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Thermostat and the Powertrain Control Module (PCM).
Look for any chafed, pierced, pinched, or partially broken wires.
Look for broken, bent, pushed out or corroded terminals.
Search for any Technical Service Bulletins that may apply.
Were any problems found?

Yes

- Repair as necessary.
- Perform the PCM Verification Test.Powertrain Verification Test

No

- Replace and program the Powertrain Control Module (PCM).
- Perform the PCM Verification Test.Powertrain Verification Test