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GMC Mystery

This bulletin applies to 2014 GMC Sierra 2500/3500 4WD vehicles. In “rare” cases, customers may experience one or all of the following concerns:

1. Intermittent no-crank or no vehicle power (impression that the battery is dead).

2. Volt gauge fluctuates and seems to decrease when a high load accessory is turned on (headlamps, wipers, etc.).

3. IPC backlighting flickers or IPC goes blank.

4. Diagnostic code B1325 set in several modules followed with DTC C0900 set in the EBCM.

5. Radio clock resets.

6. Intermittent stall with DIC indication of battery low.

7. HVAC temperature actuator defaults to hot.

8. Door locks cycle.

When diagnosing any of the above concerns and a cause for the concern can’t be identified, check the following:

1. Remove the 175 amp Mega Fuse and inspect for arcing. If any arcing is found, replace the affected components.

2. When re-installing the 175 amp Mega Fuse, torque fasteners that attach the mega fuse to the positive cables to specification found in the service manual.

3. Check the voltage drop reading on the positive battery cable that runs from the battery to the underhood buss electrical center.

4. Check the voltage drop reading on the negative battery cable that runs from the battery to the engine block.

NOTE: When checking voltage drops on steps 3 and 4 above, the voltage drop should be performed with the fuel injectors disabled and while cranking the engine. MIN/MAX on the digital multi meter should not be used. The voltage drop should be monitored at a steady crank. The voltage drop should not exceed 200 mV. If voltage drop is above 200 mV, replace the affected cable.

5. Check the cable that runs from the battery to the starter for proper torque, terminal connections and for an open circuit. Starter cable open circuit would be checked only when both ends of the starter cables are disconnected at the battery and starter, using a DVOM.

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