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Power Mode Mismatch

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 body control module (BCM) controls the ignition run relay through the control circuit by applying voltage to the ignition run relay coil control circuit. The ignition run relay is energised when the vehicle is in Service Mode, the vehicle is ON or when a remote start is requested. This is part of the BCM's primary function in controlling the vehicle power mode.

The keyless entry control module controls the back-up power for the ignition run relay through the control circuit by applying voltage to the ignition voltage circuit. This circuit is a pass-thru in the BCM and will energise the ignition circuit when the vehicle is in Service Mode, the vehicle is ON or when a remote start is requested.

Reference Information

Schematic Reference

    •  Power Distribution Schematics
    •  Power Moding Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Power Mode Description and Operation

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

Verify DTC B144B is not set.

⇒If the DTC is set, refer to DTC B144B .

Circuit/System Testing

Danger: Always perform the High-Voltage Disabling procedure prior to servicing any High-Voltage component or connection. Personal Protection Equipment (PPE) and proper procedures must be followed.

The High-Voltage Disabling procedure will perform the following tasks:

   • Identify how to disable high-voltage.
   • Identify how to test for the presence of high-voltage.
   • Identify conditions under which high voltage is always present and personal protection equipment (PPE) and proper procedures must be followed.
Before working on any high-voltage system, be sure to wear the following Personal Protection Equipment:
   • Safety glasses with appropriate side shields when within 15 metres (50 feet) of the vehicle, either indoors or outdoors.
   • Certified and up-to-date Class "0" Insulation gloves rated at 1,000 V with leather protectors.
      - Visually and functionally inspect the gloves before use.
      - Wear the Insulation gloves with leather protectors at all times when working with the high-voltage battery assembly, whether the system is energised or not.
Failure to follow the procedures exactly as written may result in serious injury or death.

Danger: The Volt Battery Pack will utilise an exchange program. Please consult the most recent revision of bulletin/PI #PIP4841, available in Service Information (SI), for a list of approved Volt Battery Pack service procedures. Components that may be removed and serviced without exchanging the complete battery pack are identified in the bulletin/PI. Please contact the GM Technical Assistance Centre (1-877-446-8227) if you have any questions.

  1. Vehicle OFF, disconnect the KR74 ignition run relay.
  2. Vehicle OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 10 Ω between the ground circuit terminal 85 and ground.
    3. ⇒If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Vehicle in Service Mode, verify that a test lamp illuminates between the relay B+ circuit terminal 30 and earth.
    4. ⇒If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  4. Connect a test lamp between the control circuit terminal 86 and earth.
  5. Cycle the power mode between Vehicle in Service Mode and Vehicle OFF. The test lamp should turn ON and OFF when changing S83 vehicle ON/OFF switch positions.
    6. ⇒If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the K9 body control module.
    ⇒If the test lamp is always OFF, test the control circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the K9 body control module.

    Note: If you are working on a module that requires high-voltage disabling, perform steps 6 and 7.

  6. Perform the High-Voltage Disabling procedure before proceeding with this diagnostic. Refer to High Voltage Disabling .
  7. Reconnect the 12 V battery.
  8. Disconnect the harness connector at the appropriate control module.
  9. Vehicle OFF, verify that a test lamp does not illuminate between the ignition circuit at the module and earth.
    10. ⇒If the test lamp does illuminate, test the ignition circuit for a short to voltage. If the circuit tests normal, test or replace the KR74 ignition run relay.
  10. Vehicle in Service Mode, verify that a test lamp illuminates between the ignition circuit at the module and earth.
    11. ⇒If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the KR74 ignition run relay.
  11. If all circuits test normal, replace the control module.

Component Testing
  1. Vehicle OFF, disconnect the KR74 ignition run relay.
  2. Test for 70-150 Ω between terminals 85 and 86.
    3. ⇒If the resistance is not within the specified range, replace the KR74 ignition run relay.
  3. Test for infinite resistance between the following terminals:
    4. • 30 and 86
    • 30 and 87
    • 30 and 85
    • 85 and 87
    ⇒If less than specified, replace the KR74 ignition run relay.
  4. Install a 3 A fused jumper wire between relay terminal 86 and 12 V. Install a jumper wire between relay terminal 85 and earth. Measure for less than 5 Ω between terminals 87 and 30.
    5. ⇒If greater than specified, replace the KR74 ignition run relay.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

    •  Relay Replacement : Within an Electrical Center → Attached to Wire Harness
    • Control Module References for the appropriate control module replacement, programming and set-up
   


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