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HOMESERVICE MANUALSCHEVROLET2012CHEVY EXPRESS G2500, VAN PASSENGER, 4.8L ENG VIN AREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 1374 (ENGINE CONTROLS AND FUEL - 4.8L, 5.3L, 6.0L, 6.2L - DTC P0230 TO DTC P0690)DTC P0340CIRCUIT/SYSTEM TESTING
2012 Chevrolet Chevy Express G2500, Van Passenger, 4.8L Eng VIN A

Circuit/System Testing

2012 Chevrolet Chevy Express G2500, Van Passenger, 4.8L Eng VIN ASECTION Circuit/System Testing
WARNING: This page is about a different car, the 2009 GMC Sierra, 2009 GMC Cab & Chassis Sierra, 2009 Chevrolet Silverado, and 2009 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the harness connector at the camshaft position (CMP) sensor.
  2. Test for less than 1 ohm on the CMP low reference circuit, terminal B, and ground.
    • If greater than the specified value, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  3. Ignition ON, test for 4.8-5.2 volts between the CMP 5-volt reference circuit terminal A and ground.
    • If less than the specified range, test the 5-volt reference circuit for an open/high resistance or short to ground. 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.
  4. Ignition ON, test for 4.8-5.2 volts between the CMP signal circuit terminal C and ground.
    • If less than the specified range, test the signal circuit for an open/high resistance or short to ground. If the circuit tests normal, replace the ECM.
    • If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  5. Ignition OFF, connect a fused jumper wire to the CMP signal circuit terminal C.
  6. Ignition ON, momentarily touch the other the other end of the fused jumper wire to the battery negative post. The scan tool should show the CMP Active counter incrementing.
    • If the CMP Active counter increments, test or replace the CMP sensor.
    • If the CMP Active counter does not increment, replace the ECM.
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Stop DIY work and contact a certified mechanic immediately if any of the following apply:

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  • • 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.
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