• 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.

For symptom byte information refer to Symptom Byte List

The body control module (BCM) controls the ignition main (underhood) and ignition main (rear body) relays through the control circuit by applying voltage to the ignition run/crank relay coil control circuit. The ignition main (underhood) and ignition main (rear body) relays are energized when the ignition switch is in the RUN or the CRANK position, or when a remote start is requested

System voltage greater than 9 V.

The ignition output is not active and a short to battery is detected 3 consecutive times on the ignition voltage circuit.

A short to ground is detected on the ignition main relay coil control circuit.

The ignition output is not active and an open is detected 20 consecutive times on the ignition voltage circuit.

No action is taken.

The ignition main (underhood) and ignition main (rear body) relays are deactivated when the fault is set. After 100 ms, the ignition main (underhood) and ignition main (rear body) relays will be activated. If the fault is still set, the relays will be deactivated. The ignition main (underhood) and ignition main (rear body) relays will again be activated after 100 ms. If this also results in a fault, the ignition main (underhood) and ignition main (rear body) relays will be deactivated until a new ignition request is received.

• The current DTC will clear when the malfunction is no longer present and an ignition request is received.
• A history DTC will clear after 40 malfunction-free ignition cycles.

A short to voltage on the ignition run/crank relay coil control will cause the engine to remain running after the mode is changed to OFF.

Power Moding Schematics

Master Electrical Component List

Power Mode Description and Operation

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

Control Module References for scan tool information

1. Ignition ON.
2. Verify the appropriate devices controlled by the KR73 Ignition Main Relay (underhood) and the KR73 Ignition Main Relay (rear body) turn ON and OFF when commanding the Run/Crank relay On and Off with a scan tool.
• If the appropriate devices controlled by the KR73 Ignition Main Relay (underhood) or KR73 Ignition Main Relay (rear body) do not turn ON and OFF

  Refer to Circuit/System Testing.

• If the appropriate devices controlled by the KR73 Ignition Main Relay (underhood) and KR73 Ignition Main Relay (rear body) turn ON and OFF
3. All OK.

1. Ignition OFF, disconnect the KR73 Ignition Main Relay (underhood) and the KR73 Ignition Main Relay (rear body), It may take up to 2 min for all vehicle systems to power down.
2. Test for less than 10 Ω between the ground circuits listed below and ground.
• KR73 Ignition Main Relay (underhood) – Ground circuit terminal 85
• KR73 Ignition Main Relay (rear body) – Ground circuit terminal 2
• If 10 Ω or greater
1. Ignition OFF.
2. Test for less than 2 Ω in the ground circuit end to end.
• If 2 Ω or greater, repair the open/high resistance in the circuit.
• If less than 2 Ω, repair the open/high resistance in the ground connection.
• If less than 10 Ω
3. Ignition ON, connect a test lamp between the control circuits listed below and ground.
• KR73 Ignition Main Relay (underhood) – Control circuit terminal 86
• KR73 Ignition Main Relay (rear body) – Control circuit terminal 1
4. Verify the test lamp turns ON and OFF when commanding the Run/Crank relay On and Off with a scan tool.
• If the test lamp is always OFF
1. Ignition OFF, remove the test lamp, disconnect the harness connector at the K9 Body Control Module.
2. Test for infinite resistance between the control circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance
3. 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, replace the K9 Body Control Module.
• If the test lamp is always ON
1. Ignition OFF, remove the test lamp, disconnect the harness connector at the K9 Body Control Module, ignition ON.
2. Test for less than 1 V between the control circuit and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the K9 Body Control Module.
• If the test lamp turns ON and OFF
5. Test or replace the appropriate KR73 Ignition Main Relay (underhood) or the KR73 Ignition Main Relay (rear body).

1. Ignition ON, disconnect the X2 harness connector at the K84 Keyless Entry Control Module.
2. Verify a test lamp illuminates between the B+ circuit terminal 1 and ground.
• If the test lamp does not illuminate and the circuit fuse is good
1. Ignition OFF, remove the test lamp.
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 good and there is voltage at the fuse.
• If the test lamp does not illuminate and the circuit fuse is open
1. Ignition OFF, remove the test lamp.
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 K84 Keyless Entry Control Module.
• If the test lamp illuminates
3. Ignition OFF, connect the X2 harness connector at the K84 Keyless Entry Control Module and disconnect the X3 harness connector at the K9 Body Control Module.
4. Test for less than 1 V between the ignition circuit terminal 6 and ground.
• If 1 V or greater

  Repair the short to voltage on the circuit.

• If less than 1 V
5. Ignition ON.
6. Verify a test lamp illuminates between the ignition circuit terminal 6 and ground.
• If the test lamp does not illuminate
1. Ignition OFF, remove the test lamp.
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.
3. 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, replace the K84 Keyless Entry Control Module.
• If the test lamp illuminates
7. Ignition OFF, remove the test lamp, connect the X3 harness connector at the K9 Body Control Module.
8. Ignition OFF, disconnect the KR73 Ignition Main Relay (underhood) and the KR73 Ignition Main Relay (rear body). It may take up to 2 min for all vehicle systems to power down.
9. Test for less than 10 Ω between the ground circuits listed below and ground.
• KR73 Ignition Main Relay (underhood) – Ground circuit terminal 85
• KR73 Ignition Main Relay (rear body) – Ground circuit terminal 2
• If 10 Ω or greater
1. Ignition OFF.
2. Test for less than 2 Ω in the ground circuit end to end.
• If 2 Ω or greater, repair the open/high resistance in the circuit.
• If less than 2 Ω, repair the open/high resistance in the ground connection.
• If less than 10 Ω
10. Ignition ON, connect a test lamp between the control circuits listed below and ground.
• KR73 Ignition Main Relay (underhood) – Control circuit terminal 86
• KR73 Ignition Main Relay (rear body) – Control circuit terminal 1
11. Verify the test lamp turns ON and OFF when commanding the Run/Crank relay On and Off with a scan tool.
• If the test lamp is always OFF
1. Ignition OFF, remove the test lamp, disconnect the harness connector at the K9 Body Control Module.
2. Test for infinite resistance between the control circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance
3. 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, replace the K9 Body Control Module.
• If the test lamp is always ON
1. Ignition OFF, remove the test lamp, disconnect the harness connector at the K9 Body Control Module, ignition ON.
2. Test for less than 1 V between the control circuit and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the K9 Body Control Module.
• If the test lamp turns ON and OFF
12. Test or replace the KR73 Ignition Main Relay (underhood) or the KR73 Ignition Main Relay (rear body).

Perform the Diagnostic Repair Verification after completing the repair.

• Control Module References for control module replacement, programming and setup.