Circuit/System Testing

2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6SECTION Circuit/System Testing
WARNING: This page is about a different car, the 2008 Cadillac STS. However, it is still accessible from the selected car via links, so may be relevant.

Diagnostic Indicator Pattern 1

  1. Enter the diagnostic mode. Refer to Diagnostic Trouble Code (DTC) DisplayingΒ .
  2. Verify that the Diagnostic Indicator Pattern 1 does not display as shown in the diagnostic indicator list. Refer to Diagnostic Trouble Code (DTC) DisplayingΒ .
    • If the Diagnostic Indicator Pattern displays after entering the diagnostic mode, proceed to the next Diagnostic Indicator Pattern displayed.
  • If the Diagnostic Indicator Pattern 1 does not display after successfully entering the diagnostic mode, test the rear park assist diagnostic input circuit terminal 16 for a short to voltage or an open/high resistance. If the circuit tests normal, test or replace the rear object sensor control module.

Diagnostic Indicator Pattern 2, 3, 4 and 5

  1. Ignition OFF, disconnect the harness connector at the suspect rear object sensor.
  2. Test for less than 1 ohm of resistance between the low reference circuit terminal 2 and ground.
    • If greater than the specified range, test the low reference circuit for an open/high resistance.
  3. Ignition ON, with the transmission in reverse, test for 8.2-8.8V between the supply voltage circuit terminal 3 and the low reference circuit terminal 2.
    • If less than the specified range, test the supply voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the rear object sensor control module.
    • If greater than the specified range, test the supply voltage circuit for a short to battery. If all circuit tests normal, replace the rear object sensor control module.
  4. Ignition ON, with the transmission in reverse, test for 7.2-9.2V between the signal circuit terminal 1 and the object sensor low reference circuit terminal 2.
    • If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the rear object sensor control module.
    • If greater than the specified range, test the signal circuit for a short to battery. If all circuit tests normal, replace the rear object sensor control module.
  5. If all circuits test normal, test or replace the suspect rear object sensor(s).

Diagnostic Indicator Pattern 6

  1. Ignition OFF, disconnect the harness connector at the rear object sensor control module.
  2. Ignition ON, test for 9.5V between the chime control circuit terminal 22 and ground.
    • If less than the specified value, test the chime control circuit for a short to ground or an open/high resistance. If all circuits test normal, replace the body control module (BCM).

Diagnostic Indicator Pattern 7

    IMPORTANT: When entering the diagnostic mode, it is necessary to follow the instructions as indicated. Refer to Diagnostic Trouble Code (DTC) DisplayingΒ . If the vehicle is not shifted into reverse within 5 seconds after turning the ignition ON, the diagnostic mode will still be initiated but a reverse input wiring fault will be registered as Diagnostic Indicator Pattern 7 as shown in the indicator list.
  1. Verify that the Diagnostic Indicator Pattern 7 displays as shown in diagnostic indicator list.

Diagnostic Indicator Pattern 8 and 9

    IMPORTANT: Diagnostic indicator patterns 8 or 9 are displayed in sequence of diagnostic indicator patterns 2, 3, 4 and 5.
  1. While still in the diagnostic mode, disconnect the rear object sensor(s) one at a time and verify that the indicator pattern 8 or 9 does not display after the suspect sensor(s) has been disconnected. When the suspect sensor(s) is disconnected, the indicator pattern 8 or 9 should no longer be displayed.
    • If the indicator pattern 8 or 9 continues to display after each sensor has been disconnected and reconnected, test the object sensor supply voltage circuit and the low reference circuit for a short to ground or an open/high resistance. If circuit tests normal, replace the rear object sensor control module.
    • If the indicator pattern 8 and 9 does not display after disconnecting the suspect sensor, replace the suspect sensor.
  2. If all circuits test normal, replace the object sensor control module.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • β€’ You smell fuel, burning insulation, or see smoke.
  • β€’ Brakes feel soft, pull hard to one side, or make grinding noises.
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