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.
SYS.OK|MANUAL.DBβ LIVE
HOMESERVICE MANUALSGMC2013RV CUTAWAY 4.8L ENG VIN AREPAIR AND DIAGNOSISENGINE PERFORMANCESYSTEMDATA COMMUNICATION SYSTEMDIAGNOSTIC INFORMATION AND PROCEDURESDTC U2099CIRCUIT/SYSTEM TESTING
2013 GMC RV Cutaway 4.8L Eng VIN A
Circuit/System Testing
2013 GMC RV Cutaway 4.8L Eng VIN ASECTION Circuit/System Testing
- With the ignition OFF, disconnect the harness connector at each module on the circuit one at a time. After each disconnect, retest for current DTCs. DTC U2099 should remain current.
- If the DTC becomes history, replace the module disconnected before the DTC became history.
- Ignition OFF, disconnect the harness connector X3 at the BCM.
- With the harness connector at the modules disconnected, test for infinite resistance between the BCM high speed GMLAN serial data wake up circuit terminal X3, 19 and ground.
- If less than the specified value, test the wake up circuit for a short to ground.
- Test for less than 1 Ξ© between the BCM high speed GMLAN serial data wake up circuit terminal X3, 19 and each serial data wake up circuit terminal at each disconnected module connector.
- If greater than the specified value, test for an open/high resistance in the serial data wake up circuit. If all circuits test normal and the DTC is current, replace the BCM.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- β’ You smell fuel, burning insulation, or see smoke.
- β’ Brakes feel soft, pull hard to one side, or make grinding noises.
- β’ The engine overheats, stalls repeatedly, or misfires under load.
- β’ You are missing required tools, torque specs, or safe lifting equipment.
- β’ You are not confident in the next step or safety outcome.