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.

### Circuit/System Description

The powertrain relay, is controlled by the engine control module (ECM) depending upon input from the ignition switch. Battery positive voltage is supplied to the relay coil and switch. When the ignition switch is turned to the ON position, the ECM will provide ground on the control circuit of the powertrain relay using a low side driver. This will allow voltage through the relay switch contacts to the components. The ECM monitors the voltage level on the control circuit of the powertrain relay.

### 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

#### Scan Tool Reference

Control Module References for scan tool information

#### Special Tools

EL-43244 Relay Puller Pliers

### Circuit/System Verification

1. Cycle the ignition from OFF to ON. You should hear and feel an audible click from the KR75 Powertrain Relay. Repeat as necessary in order to verify KR75 Powertrain Relay operation.
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.

### Circuit/System Testing

1. Ignition OFF, disconnect the KR75 Powertrain Relay.
2. Ignition ON, verify a test lamp illuminates between the B+ circuit terminal 85 and ground.

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

3. Ignition OFF, connect a test lamp between the control circuit terminal 86 and the B+ circuit terminal 85.

⇒ | If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

4. Ignition ON. The test lamp should turn ON.

⇒ | If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If circuit tests normal, replace the K20 Engine Control Module (ECM).

5. Install a 20 A fused jumper wire between the B+ circuit terminal 30 and the ignition circuit terminal 87.
6. Attempt to start the engine. The engine should start.

⇒ | If the engine does not start, test the ignition circuit between the KR75 Powertrain Relay and the K20 Engine Control Module (ECM) for a short to ground or for an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

7. If all circuits test normal, test or replace the KR75 Powertrain Relay.

### Component Testing

1. Ignition OFF, disconnect the KR75 Powertrain Relay.
2. Test for 70-110 Ω between terminal 85 and 86.

⇒ | If not within the specified range, replace the KR75 Powertrain Relay.

3. Test for infinite resistance between the following terminals of the KR75 Powertrain Relay:

• | 30 and 86

• | 30 and 87

• | 30 and 85

• | 85 and 87

⇒ | If not the specified value, replace the KR75 Powertrain Relay.

4. Install a 20 A fused jumper wire between relay terminal 85 and 12 V. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 Ω between terminal 30 and 87.

⇒ | If greater than the specified range, replace the KR75 Powertrain Relay.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for ECM replacement, setup, and programming