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Test A: No Communication With Gem

  1. Check Fuse Output For Short To Ground  - Remove fuse No. 23 (5-amp) from instrument panel fuse block. Using an ohmmeter, check resistance between ground and fuse No. 23 output cavity (right terminal). Observe ohmmeter reading. Resistance should start at more than one megohm and steadily drop to less than 3 k/ohms. If resistance drops as described, go to step 7). If resistance does not drop as described, go to next step.
  2. Check Resistance  - With ohmmeter connected as specified in step 1), check resistance. If resistance is less than 10 ohms, go to step 4). If resistance is 10 ohms or more, go to next step.
  3. Check GEM  - Disconnect GEM 18-pin connector C201 from instrument panel fuse block. Disconnect, then reconnect ohmmeter as specified in step 1). If resistance is one megohm or more (resistance may drop steadily to less than 3 k/ohms), replace GEM and repeat GEM self-test. If resistance is not more than one megohm, go to next step.
  4. Check Instrument Panel Fuse Block  - Disconnect instrument panel fuse block 27-pin connector C247 and 36-pin connector C235. Using an ohmmeter, check resistance between ground and GEM connector C201 terminal No. 5. See Figure . If resistance is less than 10 k/ohms, replace instrument panel fuse block and repeat GEM self-test. If resistance is 10 k/ohms or more and vehicle is equipped with Passive Anti-Theft System (PATS)/Remote Anti-Theft Personality (RAP), go to next step. If resistance is 10 k/ohms or more and vehicle is not equipped with PATS/RAP, go to step 7).
  5. Check PATS Module  - Reconnect instrument panel fuse block connectors C235 and C247. Disconnect PATS module connector C242 (located in center of instrument panel, behind integrated control panel). Disconnect, then reconnect ohmmeter as specified in step 1). Observe ohmmeter reading. Resistance should start at more than one megohm and steadily drop to less than 3 k/ohms. If resistance drops as described, replace PATS module. Using NGS tester, repeat GEM self-test. If resistance does not drop as described and vehicle is equipped with RAP module, go to next step. If resistance does not drop as described and vehicle is not equipped with RAP module, repair short to ground in White/Yellow wire. Using NGS tester, repeat GEM self-test.
  6. Check RAP Module  - Disconnect RAP module connector C254 (located above right side of accelerator pedal). Disconnect, then reconnect ohmmeter as specified in step 1). If resistance is more than one megohm, replace RAP module. Using NGS tester, repeat GEM self-test. If resistance is one megohm or less, repair short to ground in White/Yellow wire. Using NGS tester, repeat GEM self-test.
  7. Check Power Grounds  - Disconnect GEM 26-pin connector C248 (located behind left side of instrument panel). Using an ohmmeter, check resistance between ground and GEM connector C248 terminals No. 14 (Black wire) and No. 25 (Black wire). See Fig 1 . If resistance is 5 ohms or less, go to next step. If resistance is more than 5 ohms, repair open in appropriate Black wire(s). Using NGS tester, repeat GEM self-test.
  8. Check Logic Ground  - Disconnect GEM 22-pin connector C223 (located behind left side of instrument panel). Using an ohmmeter, check resistance between ground and GEM connector C223 terminal No. 12 (Black/White wire). See Fig 2 . If resistance is 5 ohms or less, go to next step. If resistance is more than 5 ohms, repair open in Black/White wire. Using NGS tester, repeat GEM self-test.
  9. Check Ignition Start/Run Input  - Disconnect GEM 16-pin connector C236 (located behind left side of instrument panel). Turn ignition switch to RUN position. Using a voltmeter, check voltage between ground and GEM connector C236 terminal No. 14 (Red/Yellow wire). See Fig 3 . If battery voltage exists, go to next step. If battery voltage does not exist, repair open in Red/Yellow wire. Using NGS tester, repeat GEM self-test.
  10. Check Black/Light Green Wire  - Using an ohmmeter, check resistance between ground and GEM connector C223 terminal No. 22 (Black/Light Green wire). See Fig 2 . If resistance is 5 ohms or less, go to MODULE COMMUNICATIONS NETWORK article to diagnose ISO 9141 communication link. If resistance is more than 5 ohms, repair open in Black/Light Green wire. Using NGS tester, repeat GEM self-test.
Fig 1: Identifying GEM Connector C248 Terminals
G95H34923Courtesy of FORD MOTOR CO.
Fig 2: Identifying GEM Connector C223 Terminals
G95I34924Courtesy of FORD MOTOR CO.
Fig 3: Identifying GEM Connector C236 Terminals
G97I28124Courtesy of FORD MOTOR CO.
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