Circuit/System Testing

2006 Chevrolet Chevy Express G2500, Van Cargo, 6.6 2SECTION Circuit/System Testing
WARNING: This page is about a different car, the 2008 GMC Yukon and 2008 Chevrolet Tahoe. However, it is still accessible from the selected car via links, so may be relevant.
    IMPORTANT: Ensure the engine harness connector is properly mated to the ATFP control module and the transmission auxiliary pump motor is properly mated to the ATFP control module before continuing with circuit/system testing. Refer to Diagnostic Aids.
  1. Ignition OFF, disconnect ATFP X1 connector.
  2. Ignition ON, test for battery voltage on the ATFP battery circuit, from ATFP X1 connector terminal A and chassis ground.
    • If less than battery voltage, test the ATFP battery circuit for an open/high resistance. If the circuit tests normal, continue with diagnosis.
  3. IMPORTANT: If an open ground condition is observed, inspect the 3 phase motor shield circuit and terminal for damage.
  4. Test for battery voltage on the ATFP battery circuit from ATFP X1 connector terminal A and the ATFP ground circuit connector X1 terminal C.
    • If less than the specified range, test the ATFP ground circuit for an open/high resistance. If the circuit tests normal, continue with diagnosis.
  5. Test for battery voltage on the ATFP ignition circuit from ATFP X1 connector terminal E and the ATFP ground circuit connector X1 terminal C.
    • If less than the specified range, test the ATFP ignition circuit for an open/high resistance. If the circuit tests normal, continue with diagnosis.
  6. Test for 4.8-5.2 volts on the Trans. Aux. Oil Pump Diagnostic circuit, from the ATFP X1 connector terminal D and ground.
    • If less than the specified range, test the Trans. Aux. Oil Pump Diagnostic circuit for an open/high resistance. If the circuit tests normal, replace the PIM.
    • If more than the specified range, test the Trans. Aux. Oil Pump Diagnostic circuit for a short to voltage. If the circuit tests normal, replace the PIM.
  7. Connect the J 38522Β  variable signal generator red terminal to the Trans. Aux. Oil Pump Diagnostic circuit, ATFP X1 connector terminal D. Connect the J 38522Β  variable signal generator black terminal to chassis ground.
  8. Adjust the signal generator to 50 percent duty cycle @ 250 Hz and observe the Trans. Aux. Pump Actual speed parameter with the scan tool. The scan tool should display 100 percent.
    • If less than 100 percent, test the Trans. Aux. Oil Pump Diagnostic circuit for a short to 5V. If the circuit tests normal, replace the PIM.
    • If 100 percent is displayed, 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:

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