The engine control module (ECM) creates the engine coolant temperature gage output signal by pulsing the circuit to ground. The ECM monitors the voltage on the engine coolant temperature gage output circuit. If the ECM determines that the voltage is out of the normal operating range, a DTC sets.

DTC P1691 is a Type C DTC.

DTC P1691 is a Type C DTC.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

J 33431-C Signal Generator and Instrument Panel Tester

1. Engine running, observe the DTC information with a scan tool. DTC P1691 should not set.

⇒	If DTCs P0654 or P0656 are also set, refer to Symptoms - Displays and Gages for further diagnosis of the instrument panel cluster (IPC).

2. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

1. Ignition OFF, disconnect the harness connector at the engine control module.
2. Ignition OFF, connect the J 33431-C to the engine coolant temperature gage output signal circuit at the ECM harness connector and a good ground.
3. Ignition ON, set the J 33431-C to generate a speedometer signal. The engine coolant temperature gage should change.

⇒	If the gage changes, replace the ECM.

⇒	If the gage does not change, test the engine coolant temperature gage output signal circuit for the following conditions:

•

Open

•	Short to ground

•	Short to voltage

•	High resistance

⇒	If the circuits test normal, replace the IPC.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.