For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category

### DTC Descriptor

DTC P0691: Cooling fan Relay 1 Control low voltage
DTC P0692: Cooling fan Relay 1 Control high voltage

### Circuit/System Description

The engine control module (ECM) controls the low speed cooling fan operation by grounding the low speed fan relay control circuit with an internal solid state device called a driver. For high speed cooling fan operation, the ECM grounds the high speed a relay control circuit at the same time the low speed control circuit is grounded. Battery positive voltage is supplied to the low speed, high speed relay. When the ECM is commanding a fan relay ON, the voltage of the control circuit should be low, near 0 volts. When the ECM is commanding a fan relay OFF, the voltage potential of the control circuit should be high, near battery voltage.

### Conditions for Running the DTC

• | The ignition is ON.

• | The system voltage is between 9-18 volts.

### Conditions for Setting the DTC

• | An imcorrect voltage level has been detected on the cooling fan relay control circuit.

• | The condition must be present for a minimum of 30 seconds.

### Action Taken when the DTC Sets

DTCs P0691 and P0692 are type B DTCs.

### Conditions for Clearing the MIL/DTC

DTCs P0691 and P0692 are type B DTCs.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

• | Charging System Test

#### Scan Tool Reference

Control Module References

### Circuit/System Verification

Ignition ON, command each relay ON and OFF with a scan tool. Feel or listen to verify that each relay turns ON and OFF with each command.

### Circuit/System Testing

1. Ignition OFF, disconnect the appropriate fan relay.
2. Ignition ON, verify that a test lamp does not illuminate between the earth terminal and a known ground.

⇒ | If the test lamp illuminates, test the earth circuit for a short to voltage.

3. Ignition ON, Connect a test lamp between the control circuit terminal and a known ground.

Command the relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

⇒ | If the test lamp is always ON, test the relay control circuit for a short to voltage. If the circuit tests normal replace the ECM.

⇒ | If the test lamp is always OFF, test the relay control circuit for a short to ground or an open/high resistance. If the circuit tests normal replace the ECM.

4. Connect a test lamp between the Battery + terminal and a known ground.

⇒ | If the test lamp does not activate, test the Battery + for a short to ground or an open/high resistance.

5. Connect a 30A fusible link wire between the battery positive post and the fan voltage supply circuit terminal and verify fan activation.

⇒ | If the fan does not activate, test the fan voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the fan.

6. If all circuits test normal replace the affected relay.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

### Repair Verification

Ignition ON, command the relay ON and OFF with a scan tool. Feel or listen to verify that the relay turns ON and OFF with each command.