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HOMESERVICE MANUALSCHEVROLET2009TAHOE BASE, 4.8 CREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 286 (HYBRID ENGINE CONTROLS - DTC P181C TO DTC P2792)DTC P2797CIRCUIT/SYSTEM TESTINGNOTES
2009 Chevrolet Tahoe Base, 4.8 C

Circuit/System Testing: Notes

2009 Chevrolet Tahoe Base, 4.8 CSECTION Notes
WARNING: This page is about a different car, the 2010 GMC Yukon, 2010 Chevrolet Tahoe, and 2010 Cadillac Escalade. However, it is still accessible from the selected car via links, so may be relevant.
  1. Inspect for DTC P0C2B. Diagnose P0C2B before performing this procedure.
  2. Ignition ON, engine OFF, observe the Aux. Trans. Fluid Pump Fault Status 1 and Aux. Trans. Fluid Fault Status 2 displays with the scan tool.
  3. Command the aux. trans. fluid pump speed to 50 percent with the scan tool while observing the fault status displays.
    • Refer to the applicable diagnostic procedure below for the fault status indicated by the scan tool display.
    • If No Fault status is displayed, review the Freeze Frame/Failure Records and perform the diagnosis indicated by the Fault Status parameter display.

PWM Input Fault

  1. Ignition OFF, disconnect PIM connector X1.
  2. Ignition ON, test for 11-13V on the Trans. Aux. Oil Pump Control circuit from PIM connector X1 terminal 3 and chassis ground.
    • If less than the specified range, test the control circuit for an open or short to ground. If the circuit tests normal, replace the ATFP Control Module.
    3. NOTE: Only connect the J 38522:  variable signal generator to the auxiliary transmission fluid pump control circuit when adjusted to 50 percent duty cycle. Duty cycles of less than 50 percent may damage the auxiliary transmission fluid pump assembly.
  3. Pre-Adjust the J 38522:  variable signal generator to 50 percent duty cycle @ 250 Hz.
  4. Connect the J 38522:  variable signal generator to the Trans. Aux. Oil Pump Control circuit, from the PIM connector X1 terminal 3 and ground and listen for auxiliary transmission fluid pump motor operation.
    • If pump operation is audible, replace the PIM.
    • If pump operation is not audible, continue with Circuit/System Testing.
  5. Ignition OFF, disconnect the ATFP control module connector X1.
  6. Ignition ON, test for 0V on the Trans. Aux. Oil Pump control circuit from PIM connector X1 terminal 3 and chassis ground.
    • If greater than the specified range, test the control circuit for a short to voltage.
    • If equal to the specified range, replace the ATFP 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:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.