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.
2002 Ford Mustang Base, 2D Convertible, AutomaticFACTORY OEM SERVICE PROCEDURE
Test A: No Communication With Generic Electronic Module
NOTE:
Perform all voltage and resistance tests using a Digital Volt-Ohm Meter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure. Use ohmmeter to isolate wiring harness shorts or opens.
- Turn ignition switch to RUN position. Measure voltage between ground and input side of Central Junction Box (CJB) fuses No. 32 (15-amp) and No. 39 (5-amp). CJB is located behind left side of instrument panel, next to Generic Electronic Module (GEM). See Figure and Fig 1 . If battery voltage exists at both terminals, go to next step. If battery voltage does not exist at either terminal, repair power supply circuit to appropriate fuse as necessary. After repair, test system for normal operation.
- Ensure fuses No. 32 and 39 are installed. Turn ignition switch to LOCK position. Disconnect Generic Electronic Module (GEM) 4-pin harness connector C201b. See Fig 2. GEM is located behind left side of instrument panel, next to CJB. See Figure. Measure voltage between ground and GEM harness connector C201b terminal No. 1 (White/Yellow wire). If battery voltage exists, go to next step. If battery voltage does not exist, repair open circuit in White/Yellow wire between GEM and fuse No. 39. For POWER DISTRIBUTION circuit identification, see WIRING DIAGRAMS . After repair, test system for normal operation.
- Disconnect 26-pin GEM harness connector C201e. See Fig 3. Turn ignition switch to RUN position. Measure voltage between ground and GEM harness connector C201e terminal No. 22 (Black/Pink wire). If battery voltage exists, go to next step. If battery voltage does not exist, repair open circuit in Black/Pink wire between GEM and fuse No. 32. For POWER DISTRIBUTION circuit identification, see WIRING DIAGRAMS . After repair, test system for normal operation.
- Turn ignition switch to LOCK position. Measure resistance between ground and GEM harness connector C201b terminal No. 2 (Black/White wire). If resistance is 5 ohms or less, repair module communication concern. See MODULE COMMUNICATIONS NETWORK - MUSTANG article. If resistance is more than 5 ohms, repair open circuit in Black/White wire between GEM and ground point G204. Ground point G204 is located behind center of instrument panel. See Figure. For GROUND DISTRIBUTION circuit identification, see WIRING DIAGRAMS . After repair, clear DTCs, repeat self-test and check system for normal operation.
Factory Service Tools
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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.