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Funky Fluctuations

Owners of or technicians working on 2013 GMC Yukon 4WD vehicles may experience one or all of the following concerns:

  • Intermittent no-crank or no vehicle power (giving the impression of a dead battery).
  • Volt gauge fluctuations that seem to decrease when a high load accessory is turned on (headlamps, wipers, etc.).
  • IPC backlighting flickers or goes blank.
  • DTC B1325 is set in several modules followed with DTC C0900 set in the EBCM.
  • Radio clock resets.
  • Intermittent stall (the customer would have noted a DIC indication of “Battery Low” or the battery lamp illuminated).
  • HVAC temperature actuator defaults to hot.
  • Door lock cycles.

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 type of 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 specifications 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 (UBEC).

4. Check the voltage drop reading on the negative battery cable that runs from the battery to the engine block. When checking voltage drop, this should not be performed with the fuel injectors disabled and while cranking the engine. MIN/MAX on the digital multimeter should not be used. The voltage drop should be monitored at a steady crank. The voltage drop should not exceed 200 mV. If the 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 battery and starter) with a DVOM.

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