Test I: No Communication With Gem/CTM Module
- Check fuse No. 25 (7.5-amp) in fuse junction panel and maxi-fuse No. 1 (60-amp) in battery junction box. If fuses are okay, go to next step. If maxi-fuse No. 1 is blown, replace fuse and retest system. If fuse blows again, check for short to ground in Tan/Black wire. Repair as necessary. If fuse No. 25 is blown, replace fuse and retest system. If fuse blows again, check for short to ground in White/Yellow wire. Repair as necessary.
- Measure voltage between ground and fuse junction panel fuse No. 25 terminal No. 2 (Tan/Black wire). If voltage is more than 10 volts, go to next step. If voltage is less than 10 volts, repair Tan/Black wire. Clear DTCs and retest system.
- Disconnect GEM 18-pin connector C283. Measure voltage between ground and GEM 18-pin connector terminal No. 11 (White/Yellow wire). If voltage is more than 10 volts, go to next step. If voltage is less than 10 volts, repair White/Yellow wire. Clear DTCs and retest system.
- Disconnect GEM 26-pin connector C280. Measure resistance between ground and GEM 26-pin connector terminals No. 14 and 26 (Black/White wires) individually. See Figure. If resistance is less than 5 ohms, go to next step. If resistance is more than 5 ohms, repair open in Black/White wire(s). Clear DTCs and retest system.
- Measure resistance between ground and GEM 18-pin connector Black wire terminal No. 18. See Fig 1. If resistance is less than 5 ohms, diagnose network concern. See appropriate MODULE COMMUNICATIONS NETWORK article. If resistance is more than 5 ohms, repair open in Black wire. Clear DTCs and retest system.
Courtesy of FORD MOTOR CO.