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.

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
B+ terminal 30 | 1 | 1 | -- | --
Coil Control terminal 86 | -- | 1 | 3 | --
Control Output terminal 87 | 1 | 1 | 3 | --
Coil Ground terminal 85 | -- | 1 | -- | --
1. No crank 2. Cranks in any gear 3. Cranks all the time

### Circuit/System Description

When the ignition switch is placed in the START position, a discrete signal is supplied to the body control module (BCM) notifying it that the ignition is in the START position. The BCM then sends a message to the engine control module (ECM) that crank has been requested. The ECM then verifies that the clutch pedal is fully depressed and conditions are acceptable for engine cranking. If it is, the ECM then supplies 12 volts to the control circuit of the crank relay. When this occurs, battery voltage is supplied through the switch of the crank relay to S terminal of the starter solenoid.

### Reference Information

#### Schematic Reference

Starting and Charging Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Starting System Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

Control Module References for scan tool information

### Diagnostic Aids

On manual transmission vehicles, with the clutch fully depressed, the clutch pedal position sensor signals the ECM that conditions are acceptable for cranking.

### Circuit/System Verification

1. Ignition ON, verify that no starter relay, theft deterrent, or clutch pedal position sensor DTCs are set that would cause the ECM not to enable engine starting.

⇒ | If DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle

2. Ignition ON, observe the scan tool ECM Crank Request Signal parameter. Place ignition switch in the crank position, the parameter should display Yes.

⇒ | If not the specified value, refer to Power Mode Mismatch

3. With the transmission in neutral and clutch pedal fully depressed, verify the scan tool ECM Clutch Start Switch parameter displays Applied.

⇒ | If the ECM Clutch Start Switch parameter does not indicate Applied, refer to Clutch Pedal Position Sensor Learn

4. With the transmission in neutral and clutch pedal fully depressed, attempt to start the vehicle. The crank relay should click and the engine should begin cranking.

⇒ | If the CRNK relay does not click or the engine does not crank, refer to Crank Relay Circuit Malfunction.

### Circuit/System Testing

#### Crank Relay Circuit Malfunction

1. Ignition OFF, disconnect the crank relay.
2. Ignition OFF, test for less than 5.0 ohms between the relay ground circuit terminal 85 and ground.

⇒ | If greater than the specified range, test the relay ground circuit for an open/high resistance.

3. Ignition ON, verify a test lamp illuminates between the relay switch B+ circuit terminal 30 and ground.

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

4. Ensure the parking brake is applied and the transmission is in neutral. Momentarily install a 40 A fused jumper wire between the B+ circuit terminal 30 and the control output circuit terminal 87. The starter solenoid should engage and the engine should begin cranking.

⇒ | If the solenoid does not engage, test the control output circuit for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the starter motor.

5. Connect a test lamp between the coil control circuit terminal 86 and the coil ground circuit terminal 85.
6. With the transmission in neutral and the clutch pedal fully depressed, cycle the ignition between the OFF and CRANK position.
7. The test lamp should turn ON and OFF when changing between the commanded states.

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

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

8. If all circuits test normal, test or replace the crank relay.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Relay Replacement

• | Starter Motor Replacement

• | Control Module References for ECM replacement, setup and programming