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HOMESERVICE MANUALSCHEVROLET2008CHEVY EXPRESS G2500, VAN CARGO, 6.6 6REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 1801 (ENGINE CONTROLS AND FUEL - 4.4L - DTC P0010 TO DTC P0158)DTC P012BCIRCUIT/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.
NOTE:
  • You must perform Circuit/System Verification before proceeding with the Circuit/System Testing.
  • The harness connectors for the following sensors are of the same configuration but are not interchangeable. Review the engine controls schematics for the BARO sensor and for the SCIAP sensor and note the circuit colors. Inspect the wiring harness of the BARO sensor for the proper connections. Inspect the wiring harness of the SCIAP sensor for the proper connections.
  1. Visually and physically inspect the integrity of the entire supercharger air induction system, for any of the following conditions:
    • A restricted or collapsed air intake duct
    • A misaligned or damaged air intake duct
    • A dirty or deteriorating air filter element
    • Any objects blocking the air inlet probe of the MAF/IAT sensor
    • Any contamination or debris on the sensing elements in the probe of the MAF/IAT sensor
    • Any water intrusion in the induction system
    • Any vacuum leak downstream of the MAF/IAT sensor
    • An intake manifold leak
    • If a condition is found, repair as necessary.
  2. Visually and physically inspect all vacuum lines for cracking, loose fit, restrictions and proper routing at the following locations:
    • The SCIAP sensor
    • The MAP sensor
    • The by-pass valve solenoid
    • The by-pass valve actuator
    • If a condition is found, repair as necessary.
  3. Visually and physically inspect the by-pass valve and cable for any of the following conditions:
    • A binding or sticking in the open or closed position
    • A binding when opening or closing
    • An incorrectly adjusted cable
    • Any damage
  4. Ignition OFF, disconnect the harness connector at the SCIAP sensor.
  5. Ignition OFF for 90 seconds, test for less than 5 ohms between the low reference circuit terminal A 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.
  6. Verify the scan tool SC Inlet Pressure Sensor parameter is less than 20 kPa.
    • If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  7. Install a 3A fused jumper wire between the 5-volt reference circuit terminal C and the signal circuit terminal B. Verify the scan tool parameter is greater than 95 kPa.
    • If less than the specified range, test the signal circuit for a short to ground, open/high resistance. If the circuit tests normal, replace the ECM.
  8. If all circuits test normal, test or replace the SCIAP sensor.
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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.