Ignition Relay: Testing and Inspection
Ignition Relay Diagnosis
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions 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.
Diagnostic Aids
The relay electrical contacts may be pitted or sticking. Replace the powertrain relay, if gently tapping or wiggling the powertrain relay causes a change in the relays operation.
Reference Information
Schematic Reference
Engine Controls Schematics [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views Fuel Pump and Level Sensor Assembly
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References Control Module References for scan tool information
Special Tools
EL 43244 - Relay Puller Pliers
For equivalent regional tools, refer to Special Tools Tools and Equipment.
Circuit/System Verification
Warning
An electric fan under the hood can start up even when the engine is not running and can injure you. Keep hands, clothing and tools away from any underhood electric fan.
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. Verify a test lamp illuminates between ground and the B+ circuit terminals listed below:
* Terminal 1
* Terminal 3
• If the test lamp does not illuminate, test the B+ circuit terminals for a short to ground or an open/high resistance.
3. Verify a test lamp does not illuminates between the control circuit terminal 5 and ground.
• If the test lamp illuminates, test the control circuit for a short to voltage.
4. Ignition OFF, verify a test lamp does not illuminate between the relay coil control circuit terminal 2 and B+.
• If the test lamp illuminates, test the relay coil control circuit for a short to ground. If the circuit tests normal, replace the K20 Engine Control Module.
5. Ignition ON. The test lamp should turn ON.
• If the test lamp is always OFF, test the coil 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 voltage circuit is between the KR75 Engine Controls Ignition Relay circuit 5 and the ECM through fuse F10. The ignition voltage is a feedback circuit.
6. Install a 15 A fused jumper wire between the KR75 Engine Controls Ignition Relay B+ circuit terminal 3 and the KR75 Engine Controls Ignition Relay control circuit terminal 5.
7. Attempt to start the engine. The engine should start.
8. If the engine does not start, test the control circuit between the KR75 Engine Controls Ignition Relay circuit terminal 5 and the ECM connector X2 terminals 13 and 28 for a short to ground or for an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module.
9. 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. Measure for 70-110 ohms between terminals 1 and 2 of the KR75 Engine Controls Ignition Relay.
• If the resistance is not within the specified range, replace the KR75 Engine Controls Ignition Relay.
3. Measure for infinite resistance between following terminals of the KR75 Engine Controls Ignition Relay:
* Terminals 3 and 1
* Terminals 3 and 5
* Terminals 3 and 2
* Terminals 2 and 5
• If continuity is detected, replace the KR75 Engine Controls Ignition Relay.
4. Connect a 20 A fused jumper wire from the positive terminal of the battery to KR75 Engine Controls Ignition Relay terminal 1. Connect a jumper wire from the negative terminal of the battery to KR75 Engine Controls Ignition Relay terminal 2. Measure for less than 5 ohms between KR75 Engine Controls Ignition Relay terminal 3 and KR75 Engine Controls Ignition Relay socket terminal 5.
• If the greater than 5 ohms, replace the KR75 Engine Controls Ignition Relay.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Relay Replacement (Within an Electrical Center) Relay Replacement (Within an Electrical Center)Relay Replacement (Attached to Wire Harness) Relay Replacement (Attached to Wire Harness)
* Control Module References Control Module References for ECM replacement, programming and setup