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.
Circuit/System Verification
2009 Chevrolet Tahoe Base, 4.8 CSECTION Circuit/System Verification
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.
- Verify that there are no DTCs in the APM that disable the 42-volt circuit, no engine-stall DTCs in the ECM, and no U-codes in any module.
- If there are any of the specified DTCs, refer to Diagnostic Trouble Code (DTC) List - Vehicle .
- Engine running, accessories OFF, measure and record the battery voltage at the battery terminals. The voltage should be between 12.6-15.0 volts.
- If not within the specified range, refer to Charging System Test .
- Engine running, observe the scan tool PSCM Intermediate Voltage parameter. The voltage should be 37.5-50 volts.
- If not within the specified range, refer to Voltage Out Of Range At All Times .
- Engine running, rotate the steering wheel left and right while stationary. Observe the scan tool PSCM Intermediate Voltage parameter. The voltage should remain greater than 37.5 volts.
- If the voltage is less than the specified range only when turning the steering wheel, refer to Low Voltage When Turning .
- Operate the vehicle on a bumpy road. Observe the scan tool APM 42V Circuit Maximum parameter. The scan tool 42V Circuit Maximum parameter should be less than 50 volts.
- If the voltage is greater than the specified range, replace the PSCM.
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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.