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 P0693: Cooling fan Relay 2 Control low voltage
DTC P0694: Cooling fan Relay 2 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 and S/P 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 and S/P fan relays. 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 P0693 and P0694 are type B DTCs.

### Conditions for Clearing the MIL/DTC

DTCs P0693 and P0694 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.