No Communication With Gem/CTM
- Using ohmmeter, check condition of maxi-fuse No. 1 (50-amp) in engine compartment fuse/relay box. If fuse is okay, go to next step. If fuse is not okay, replace fuse. Clear DTCs and retest system operation. If fuse fails again, check Tan/Black wire between engine compartment fuse/relay box and instrument panel fuse block for short to ground. Repair circuit as necessary.
- Using ohmmeter, check condition of instrument panel fuse block fuse No. 25 (7.5-amp). If fuse is okay, go to next step. If fuse is not okay, replace fuse. Clear DTCs and retest system operation. If fuse fails again, check White/Yellow wire between instrument panel fuse block and GEM/CTM for short to ground. Repair circuit as necessary.
- Measure voltage between ground and instrument panel fuse block fuse No. 25 (7.5-amp) terminal No. 2. See Fig 1
. If voltage is more than 10 volts, go to next step. If voltage is 10 volts or less, repair Tan/Black wire. Clear DTCs and retest system operation.
- Turn ignition off. Disconnect GEM/CTM 18-pin connector C224. GEM/CTM is located behind center of instrument panel. Measure voltage between ground and GEM/CTM 18-pin connector C224, terminal No. 11 (White/Yellow wire). See Figure
. If voltage is more than 10 volts, go to next step. If voltage is 10 volts or less, repair White/Yellow wire between instrument panel fuse block and GEM/CTM. Clear DTCs and retest system operation.
- Disconnect GEM/CTM 26-pin connector C221. Measure resistance between ground and GEM/CTM 26-pin connector C221, terminal No. 14 (Black/White wire). See Figure
. Measure resistance between ground and GEM/CTM 26-pin connector C221 terminal No. 26 (Black/White wire). If resistance is less than 5 ohms in both measurements, go to next step. If resistance is 5 ohms or more in either measurement, repair appropriate open circuit. Clear DTCs and retest system operation.
- Measure resistance between ground and GEM/CTM 18-pin connector C224, terminal No. 18 (Light Green/Black or Black wire). See Figure
. If resistance is less than 5 ohms, see MODULE COMMUNICATION NETWORK article to continue diagnosis. If resistance is 5 ohms or more, repair open in appropriate circuit. Clear DTCs and retest system operation.
Courtesy of FORD MOTOR CO.