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.
Pinpoint Test A: GFM2 (Generic Function Module 2) Controlled Systems Are Inoperable
- NOTE: Except for GFM2 power, ground and HS-CAN, all wiring is provided by an upfitter. REFER to upfitter documentation for wiring and system operation.
Refer to Wiring Diagrams CUSTOMER ACCESS for schematic and connector information.
Normal Operation and Fault Conditions
REFER to: Generic Function Module 2 (GFM2) .
Possible Sources
- Wiring, terminals or connectors
- Fuse(s)
- Auxiliary relays
- Auxiliary devices
- GFM2
Visual Inspection and Pre-checks
- Verify AJB fuse F47 (10A).
- Inspect the GFM2 for loose or corroded connections.
- A1 CHECK FOR CHARGING SYSTEM DIAGNOSTIC TROUBLE CODES (DTCS) SET IN OTHER MODULES
- Ignition ON.
- Connect the diagnostic tool.
- Using a diagnostic scan tool, retrieve all Continuous Memory Diagnostic Trouble Codes (CMDTCs).
Are any charging system DTCs recorded?
Yes DIAGNOSE the charging system concern. Refer to the appropriate Battery and Charging System article. No GO to A2 - A2 CHECK THE BATTERY CONDITION AND STATE OF CHARGE
- Check the battery condition and verify the battery is fully charged. REFER to: Battery .
Is the battery OK and fully charged?
Yes GO to A3 No If the battery is discharged, DIAGNOSE the cause of the low battery condition. Refer to the appropriate Battery and Charging System article. If the battery condition fails, INSTALL a new battery. REFER to: Battery - Vehicles With: Dual Batteries . - A3 CHECK GFM2 (GENERIC FUNCTION MODULE 2) POWER
- Ignition OFF.
- Disconnect GFM2 C290A.
- Ignition ON.
- Measure:
Positive Lead Measurement / Action Negative Lead C290A-1 Ground
Is the voltage within 0.5 volt of the recorded battery voltage?
Yes GO to A4 No VERIFY AJB fuse F471 (10A) is OK. If OK, REPAIR the circuit. If not OK, REFER to the OEM ELECTRICAL WIRING DIAGRAM INTRODUCTION to identify the possible causes of the circuit short to ground. - A4 CHECK GFM2 (GENERIC FUNCTION MODULE 2) GROUND
- Ignition OFF.
- Measure:
Positive Lead Measurement / Action Negative Lead C290A-4 Ground
Is the resistance less than 3 ohms?
Yes INSTALL a new GFM2. REFER to the appropriate Service Information. No REPAIR the circuit.
NO RELATED
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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.