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Ignition Relay Diagnosis

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 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 relay.

Reference Information

Schematic Reference

Engine Controls Schematics : LLW

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

Circuit/System Verification

Cycle the ignition from OFF to ON. You should hear and feel an audible click from the powertrain relay. Repeat as necessary in order to verify ignition relay operation.

Circuit/System Testing
  1. Ignition OFF, disconnect the powertrain relay.
  2. Ignition ON, verify a test lamp illuminates between the relay coil ignition 1 voltage circuit terminal 85 and ground.
    3. ⇒If the test lamp does not illuminate, repair the relay coil ignition 1 voltage 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 relay coil control circuit terminal 86 and the relay coil ignition 1 voltage circuit terminal 85.
    4. ⇒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.
  4. Ignition ON. The test lamp should turn ON.
    5. ⇒If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module.

    Note: The ignition 1 voltage circuit is between the powertrain relay and the ECM. The ignition 1 voltage is a feedback circuit.

  5. Install a 20 A fused jumper wire between the relay switch B+ circuit terminal 30 and the relay switch ignition 1 voltage circuit terminal 87.
  6. Attempt to start the engine. The engine should start.
    7. ⇒If the engine does not start, test the ignition 1 voltage circuit between the Powertrain Relay and the ECM for a short to ground or for an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module.
  7. If all circuits test normal, test or replace the Powertrain Relay.

Component Testing

Dynamic Test

  1. Ignition OFF, disconnect the Powertrain Relay.
  2. Test for 70-110 Ω between terminals 85 and 86.
    3. ⇒If not within the specified range, replace the Powertrain Relay.
  3. Test for infinite resistance between the following terminals of the Powertrain Relay:
    4. • 30 and 86
    • 30 and 87
    • 30 and 85
    • 85 and 87
    ⇒If not the specified value, replace the Powertrain Relay.
  4. Install a 20 A fused jumper wire between relay terminal 85 and B+. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 Ω between terminals 30 and 87.
    5. ⇒If greater than the specified range, replace the Powertrain Relay.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for ECM replacement, setup, and programming

   


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