• 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.

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.

Engine Controls Schematics

Master Electrical Component List

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Control Module References for scan tool information

EL 43244 Relay Puller Pliers

For equivalent regional tools, refer to Special Tools.

1. Ignition ON.
2. Verify the KR75 Engine Controls Ignition Relay clicks when cycling the ignition from OFF to ON.
• If the relay does not click

  Refer to Circuit/System Testing

• If the relay clicks
3. Verify with a scan tool that DTC P0201B, P0201D, P16F3 or P20F8 are not set.
• If DTC  P0201B, P0201D, P16F3 or P20F8 are set

  Refer to Diagnostic Trouble Code (DTC) List - Vehicle

• If DTC  P0201B, P0201D, P16F3 or P20F8 are not set
4. All OK.

1. Ignition OFF, disconnect the KR75 Engine Controls Ignition Relay. It may take up to 2 min for all vehicle systems to power down.
2. Ignition ON, verify a test lamp illuminates between the B+ circuit terminal 30 and ground.
• If the test lamp does not illuminate and the circuit fuse is good
1. Ignition OFF.
2. Test for less than 2 Ω in the B+ circuit end to end.
• If 2 Ω or greater, repair the open/high resistance in the circuit.
• If less than 2 Ω, verify the fuse is not open and there is voltage at the fuse.
• If the test lamp does not illuminate and the circuit fuse is open
1. Ignition OFF.
2. Test for infinite resistance between the B+ circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the K20 Engine Control Module.
• If the test lamp illuminates
3. Ignition ON, verify a test lamp illuminates between the ignition circuit terminal 85 and ground.
• If the test lamp does not illuminate and the circuit fuse is good
1. Ignition OFF.
2. Test for less than 2 Ω in the ignition circuit end to end.
• If 2 Ω or greater, repair the open/high resistance in the circuit.
• If less than 2 Ω, verify the fuse is not open and there is voltage at the fuse.
• If the test lamp does not illuminate and the circuit fuse is open
1. Ignition OFF.
2. Test for infinite resistance between the ignition circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the K20 Engine Control Module.
• If the test lamp illuminates
4. Ignition OFF, connect a test lamp illuminates between the control circuit terminal 86 and B+.
5. Ignition ON. Verify the test lamp illuminates.
• If the test lamp does not illuminate
1. Ignition OFF.
2. Test for less than 2 Ω in the control circuit end to end.
• If 2 Ω or greater, repair the open/high resistance in the circuit.
• If less than 2 Ω
3. Ignition OFF.
4. Disconnect the harness connector at the K20 Engine Control Module. Ignition ON
5. Test for less than 1.0 V the control circuit and ground.
• If greater than 1.0 V, repair the short to voltage.
• If less than 1.0 V, replace the K20 Engine Control Module.
• If the test lamp illuminates
6. Ignition OFF, verify the test lamp does not illuminate.
• If the test lamp illuminates
1. Ignition OFF.
2. Disconnect the harness connector at the K20 Engine Control Module. Ignition ON
3. Test for less infinitive resistance between the control circuit and ground.
• If less than infinitive resistance, repair the short to ground in the circuit.
• If infinitive resistance, replace the K20 Engine Control Module.
• If the test lamp does not illuminate
7. Install a 20 A fused jumper wire between the B+ circuit terminal 30 and the ignition circuit terminal 87.
8. Attempt to start the engine. The engine should start.
• If the engine does not start
1. Ignition OFF.
2. Test for less than 2 Ω at the ignition circuit end to end.
• If 2 Ω or greater, repair the open/high resistance in the circuit.
• If less than 2 Ω
3. Ignition OFF.
4. Disconnect the harness connector at the K20 Engine Control Module. Ignition ON
5. Test for less infinitive resistance between the control circuit and ground.
• If less than infinitive resistance, repair the short to ground in the circuit.
• If infinitive resistance, replace the K20 Engine Control Module.
• If the engine starts
9. Replace the KR75  Engine Controls Ignition Relay.

1. Ignition OFF, disconnect the KR75  Engine Controls Ignition Relay.
2. Test for 70–110 Ω between terminals 85 and 86 or 1 and 2 of the relay.
• If not within 70–100 Ω

  Replace the relay.

• If within 70–100 Ω
3. Test for infinite resistance between the following terminals listed below:
• 30 and 86 or 3 and 1
• 30 and 87 or 3 and 5
• 30 and 85 or 3 and 2
• 85 and 87 or 2 and 5
• If less than infinite resistance

  Replace the relay.

• If infinite resistance
4. Install a 20 A fused jumper wire between relay terminal 85 and B+. Install a jumper wire between relay terminal 86 or 1 and ground.
5. Test for less than 2 Ω between terminals 30 and 87.
• If 2 Ω or greater

  Replace the relay.

• If less than 2 Ω
6. All OK.

Perform the Diagnostic Repair Verification after completing the repair.

• Electrical Relay Replacement
• Control Module References for Control Module replacement, programming and setup.