Test C: No Communication With Rear Electronic Module
- Turn ignition switch to LOCK position. Disconnect Rear Electronic Module (REM) harness connectors C420d and C420c. Turn ignition switch to RUN position. Measure voltage at terminal No. 3 (Orange/Black wire) at REM harness connector C420d. See Fig 1
. Measure voltage at terminal No. 13 (Orange/Black wire) at REM harness connector C420c. If battery voltage exists at both terminals, go to next step. If battery voltage does not exist at both terminals, repair power distribution circuit as necessary. See POWER DISTRIBUTION article in WIRING DIAGRAMS.
- Turn ignition switch to LOCK position. Disconnect remaining REM harness connectors. Measure resistance between ground and terminal No. 12 (Black/Orange wire) at REM harness connector C420b. Measure resistance between ground and terminals No. 11, 12, 25 and 26 (all Black/Orange wires) at REM harness connector C420c. Measure resistance between ground and terminal No. 2 (Black/Orange wire) at REM harness connector C420d. Measure resistance between ground and terminal No. 3 (Black/Orange wire) at REM harness connector C420f. Measure resistance between ground and terminal No. 1 (Black/Orange wire) at REM harness connector C4201. If all resistances are 5 ohms or less, diagnose module communications concern. See MODULE COMMUNICATIONS NETWORK - LS
article. If any resistance is greater than 5 ohms, repair open in appropriate wire between REM and ground.
Courtesy of FORD MOTOR CO.