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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 engine controls ignition 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 engine controls ignition 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 engine controls ignition 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

For equivalent regional tools, refer to Special Tools .

Circuit/System Verification

  1. Cycle the ignition from OFF to ON. You should hear and feel an audible click from the KR75 Engine Controls Ignition Relay. Repeat as necessary in order to verify KR75 Engine Controls Ignition 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 Engine Controls Ignition Relay.
  2. Ignition ON, verify a test lamp illuminates between the B+ circuit terminal 2 and ground.
  3. 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.
  4. Ignition OFF, connect a test lamp between the control circuit terminal 1 and the B+ circuit terminal 2.
  5. 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.
  6. Ignition ON. The test lamp should turn ON.
  7. 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.
  8. Install a 20 A fused jumper wire between the B+ circuit terminal 3 and the ignition circuit terminal 5.
  9. Attempt to start the engine. The engine should start.
  10. If the engine does not start, test the ignition circuit between the KR75 Engine Controls Ignition Relay and the K20 Engine Control Module for a short to ground or for an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module.
  11. If all circuits test normal, test or replace the KR75 Engine Controls Ignition Relay.

Component Testing

Relay Test

  1. Ignition OFF, disconnect the KR75 Engine Controls Ignition Relay.
  2. Test for 70-110 Ω between terminal 85 and 86.
  3. If not within the specified range, replace the KR75 Engine Controls Ignition Relay.
  4. Test for infinite resistance between the following terminals of the KR75 Engine Controls Ignition Relay:
  5. • 3 and 1
    • 3 and 5
    • 3 and 2
    • 2 and 5
    If not the specified value, replace the KR75 Engine Controls Ignition Relay.
  6. Install a 20 A fused jumper wire between relay terminal 2 and 12 V. Install a jumper wire between relay terminal 1 and ground. Test for less than 2 Ω between terminal 3 and 5.
  7. If greater than the specified range, replace the KR75 Engine Controls Ignition Relay.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Relay Replacement : Within an Electrical Center → Attached to Wire Harness
    • Control Module References for ECM replacement, programming and setup
   


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