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HOMESERVICE MANUALSCHEVROLET2008CHEVY EXPRESS G2500, VAN CARGO, 6.6 6REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 1800 (ENGINE CONTROLS AND FUEL - 3.6L - DTC P0008 TO DTC P0193)DTC P0191CIRCUIT/SYSTEM TESTING
2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6

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 2009 Cadillac STS. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the multi-way harness connector X161 at the rear of the intake manifold.
  2. Remove the fuse that supplies B+ to terminal X2-56 of the ECM.
    3. IMPORTANT: Testing for steps 3 through 7 is performed on the ECM side of the multi-way harness connector.
  3. Ignition OFF, test for less than 5 Ξ© between the low reference circuit terminal 5 and ground.
    • If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  4. Install the fuse that supplies B+ to terminal X2-56 of the ECM.
  5. Ignition ON, test for 4.8-5.2 V between the 5-volt reference circuit terminal 11 and ground.
    • If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
    • If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  6. Ignition ON, verify the scan tool FRP sensor voltage parameter is greater than 4.96 V.
    • If less than the specified value, test the signal circuit terminal 12 for a short to ground. If the circuit tests normal, replace the ECM.
  7. Connect a 3 A fused jumper wire between the signal circuit terminal 12 and the low reference circuit terminal 5. Verify the scan tool FRP voltage parameter transitions from greater than 4.96 V to less than 0.02 V.
    • If the parameter does not transition from the maximum to minimum value, test the signal circuit for an open/high resistance or a short to voltage. If the circuit tests normal, replace the ECM.
  8. Ignition OFF, remove the intake manifold.
  9. Disconnect the FRP sensor connector.
  10. Remove the fuse that supplies B+ to terminal X2-56 of the ECM.
    11. IMPORTANT: Testing for steps 11 through 15 are performed at the FRP sensor connector.
  11. Ignition OFF, test for less than 5 Ξ© between the low reference circuit terminal 1 and ground.
    • If greater than the specified range, test the low reference circuit for an open/high resistance.
  12. Install the fuse that supplies B+ to terminal X2-56 of the ECM.
  13. Ignition ON, test for 4.8-5.2 V between the 5-volt reference circuit terminal 3 and ground.
    • If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance.
    • If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  14. Ignition ON, verify the scan tool FRP sensor voltage parameter is greater than 4.96 V.
    • If less than the specified value, test the signal circuit terminal 2 for a short to ground.
  15. Connect a 3 A fused jumper wire between the signal circuit terminal 2 and the low reference circuit terminal 1. Verify the scan tool FRP voltage parameter transitions from greater than 4.96 V to less than 0.02 V.
    • If the parameter does not transition from the maximum to the minimum value, test the signal circuit for an open/high resistance or a short to voltage.
  16. If all circuits test normal, replace the FRP sensor.
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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.