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Test D: Powertrain Control Module Does Not Respond To Scan Tool

NOTE: If test results indicate PCM is faulty, always check for any engine performance-related DTCs prior to replacing PCM. If any DTCs are present, service DTCs as necessary and retest. See SELF-DIAGNOSTICS - EEC-V (GASOLINE) article in ENGINE PERFORMANCE.
NOTE: Depending on module configuration, with all modules connected and with ignition switch in RUN position or with engine running, 2-3 volts may be present at DLC terminals No. 2 (White/Blue wire) and No. 10 (Black/Blue wire). These are Standard Corporate Protocol (SCP) diagnostic communications network circuits.
  1. Turn ignition on. Perform data link diagnostic test. See DATA LINK DIAGNOSTIC TEST  under SELF-DIAGNOSTIC SYSTEM. If scan tool indicates PCM: NO RESPONSE ON CKT 914 (BUS +), go to next step. If scan tool does not indicate PCM: NO RESPONSE ON CKT 914 (BUS +), go to step  7 .
  2. Turn ignition off. Disconnect scan tool. Disconnect PCM connector located under center console. See Figure . Inspect connector for loose, damaged or corroded terminals. Pay particular attention to terminal No. 16. Repair connector as necessary and retest system for normal operation. If connector is okay, inspect DLC for loose, damaged or corroded terminals. Pay particular attention to terminal No. 2 (White/Blue wire). Repair connector as necessary and retest system for normal operation. If connector is okay, go to next step.
  3. Measure resistance of White/Blue wire between terminal No. 16 at PCM connector and terminal No. 2 at DLC. See Figure and Fig 1 . If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, go to step  6 .
  4. Turn ignition on. Measure voltage between terminals No. 2 (White/Blue wire) and No. 16 (Green wire) at DLC. Also, measure voltage between terminals No. 2 (White/Blue wire) and No. 4 (Black wire) at DLC. See Figure . If voltage is indicated for either measurement, go to next step. If voltage is not indicated for both measurements, check engine control system operation. See SELF-DIAGNOSTICS - EEC-V (GASOLINE) article in ENGINE PERFORMANCE. Repair as necessary and retest system for normal operation.
  5. Turn ignition off. Disconnect 10-pin in-line connector C256 (White) located near PCM. See Figure . Turn ignition on. Measure voltage between terminals No. 2 (White/Blue wire) and No. 16 (Green wire) at DLC. Also, measure voltage between terminals No. 2 (White/Blue wire) and No. 4 (Black wire) at DLC. See Figure . If voltage is indicated for either measurement, repair White/Blue wire between in-line connector C256 and DLC. Retest system for normal operation. If voltage is not indicated for both measurements, repair White/Blue wire between in-line connector C256 and PCM. Retest system for normal operation.
  6. Turn ignition off. Disconnect 10-pin in-line connector C256 (White) located near PCM. See Figure . Measure resistance of White/Blue wire between terminal No. 6 at female half of in-line connector C256 and terminal No. 2 at DLC. See Figure and Fig 2 . If resistance is less than 5 ohms, repair open in White/Blue wire between in-line connector C256 and PCM. Retest system for normal operation. If resistance is 5 ohms or more, repair open in White/Blue wire between in-line connector C256 and DLC. Retest system for normal operation.
  7. Disconnect scan tool. Disconnect PCM connector located under center console. See Figure . Inspect connector for loose, damaged or corroded terminals. Pay particular attention to terminal No. 10. Repair connector as necessary and retest system for normal operation. If connector is okay, go to next step.
  8. Measure resistance of Black/Blue wire between terminal No. 15 at PCM connector and terminal No. 10 at DLC. See Figure and Fig 1 . If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, go to step  11 .
  9. Turn ignition on. Measure voltage between terminals No. 10 (Black/Blue wire) and No. 16 (Green wire) at DLC. Also, measure voltage between terminals No. 10 (Black/Blue wire) and No. 4 (Black wire) at DLC. See Figure . If voltage is indicated for either measurement, go to next step. If voltage is not indicated for both measurements, check engine control system operation. See SELF-DIAGNOSTICS - EEC-V (GASOLINE) article in ENGINE PERFORMANCE.
  10. Turn ignition off. Disconnect 10-pin in-line connector C256 (White) located near PCM. See Figure . Turn ignition on. Measure voltage between terminals No. 10 (Black/Blue wire) and No. 16 (Green wire) at DLC. Also, measure voltage between terminals No. 4 (Black wire) and No. 10 (Black/Blue wire) at DLC. See Figure . If voltage is indicated for either measurement, repair Black/Blue wire between in-line connector C256 and DLC. Retest system for normal operation. If voltage is not indicated for both measurements, repair Black/Blue wire between in-line connector C256 and PCM. Retest system for normal operation.
  11. Turn ignition off. Disconnect 10-pin in-line connector C256 (White) located near PCM. See Figure . Measure resistance of Black/Blue wire between terminal No. 10 at DLC and terminal No. 1 at female half of in-line connector C256. See Figure and Fig 2 . If resistance is less than 5 ohms, repair open in Black/Blue wire between in-line connector C256 and PCM. Retest system for normal operation. If resistance is 5 ohms or more, repair open in Black/Blue wire between in-line connector C256 and DLC. Retest system for normal operation.
Fig 1: Identifying Powertrain Control Module (PCM) Terminals
G97E28807Courtesy of FORD MOTOR CO.
Fig 2: Identifying Connector C256 Terminals (Female Half Of Connector Shown)
G98F01709Courtesy of FORD MOTOR CO.
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