Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET2008CHEVY EXPRESS G2500, VAN CARGO, 6.6 6REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 1076 (ENGINE CONTROLS AND FUEL - 6.6L (LMM) - DTC P154B TO DTC P2693)DTC P154BCIRCUIT/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 2007 GMC Sierra, 2007 GMC Cab & Chassis Sierra, 2007 Chevrolet Silverado, and 2007 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
IMPORTANT:
You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.
- Test the following circuits for an open, a short to ground, or a short to voltage:
- The IAH command 1 circuit
- The IAH command 2 circuit
- The IAH voltage signal circuit
- If a condition was found on any of the circuits repair as necessary.
- Connect any circuits that were disconnected. With the ignition ON and the engine OFF, observe that the scan tool displays the IA Heater Driver Shorted parameter as OK.
- If the IA Heater Driver Shorted parameter displays Fault, replace the intake air heater.
- With the ignition ON and the engine OFF, observe that the scan tool displays the Glow Plug Driver Shorted parameter as OK.
- If the Glow Plug Driver Shorted parameter displays Fault, replace the Glow Plug Control Module.
- Disconnect the IAH. Turn ON the ignition. With a DMM measure between command 2 circuit terminal 3 and a good ground on the harness side of the connector for 0.78-1.1 Hz.
- If the DMM does not measure between 0.78-1.1 Hz ohms, replace the GPCM.
- Do not install the jumper wire between 12 volts and the command circuit for more the 20 seconds.
- Set the DMM to the 4 v AC hertz scale.
- Turn OFF the ignition. Install a jumper wire between the IAH harness temperature signal circuit terminal 1 and the corresponding terminal on the IAH.
- Install a jumper wire between the IAH harness command two circuit terminal 3 and the corresponding terminal on the IAH.
- Supply 12 volts to terminal 2 on the IAH.
- Turn ON the ignition. Measure for 1 hertz on terminal 5 at the IAH.
- If 0.7-1.1 hertz is measured on terminal 5, replace the GPCM.
- If 0.7-1.1 hertz is not measured on terminal 5, replace the IAH.
IMPORTANT:
Set the DMM to the 4 v DC hertz scale.
IMPORTANT:
RENDER: 1.0x
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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.