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

NOTE: If test results indicate Powertrain Control Module (PCM) is faulty, always check for any PCM DTCs prior to replacing PCM. If any PCM DTCs are present, service PCM DTCs as necessary and retest system. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
NOTE: Depending on module configuration, with all modules connected and with ignition switch in ON position or with engine running, 2-3 pulsed volts may be present at Data Link Connector (DLC) terminal No. 2 (White/Blue wire) and terminal No. 10 (Black/Blue wire). These are Standard Corporate Protocol (SCP) diagnostic communications network circuits. For terminal identification, see illustration. See Figure.
  1. Perform data link diagnostic test. See DATA LINK DIAGNOSTIC TEST  under SELF-DIAGNOSTIC SYSTEM. If NGS tester displays PCM: NO RESPONSE ON CKT 914 (BUS +), go to next step. If NGS tester does not display PCM: NO RESPONSE ON CKT 914 (BUS +), go to step  7.
  2. Turn ignition switch to LOCK position. Disconnect NGS tester. Disconnect PCM harness connector. PCM is located under center console. See Figure. Inspect PCM component and harness connectors for loose, damaged or corroded terminals. Pay particular attention to harness connector terminal No. 16 (White/Blue wire). See Fig 1. Inspect DLC for loose, damaged or corroded terminals. Pay particular attention to terminal No. 2 (White/Blue wire). See Figure. If connectors are okay, go to next step. If either connector is not okay, repair connector(s) as necessary and retest system for normal operation.
  3. Measure resistance of White/Blue wire between DLC terminal No. 2 and PCM harness connector terminal No. 16. 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 switch to ON position. Measure voltage between DLC terminals No. 2 (White/Blue wire) and No. 4 (Black wire), then measure voltage between DLC terminals No. 2 (White/Blue wire) and No. 16 (Green wire). If voltage exists for either measurement, go to next step. If voltage does not exist for both measurements, check powertrain control system operation. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. Repair as necessary and retest system for normal operation.
  5. Turn ignition switch to LOCK position. Disconnect in-line harness connector C256 (White). In-line harness connector C256 is located near PCM. See Figure. Turn ignition switch to ON position. Measure voltage between DLC terminals No. 2 (White/Blue wire) and No. 4 (Black wire), then between DLC terminals No. 2 (White/Blue wire) and No. 16 (Green wire). If voltage exists for either measurement, repair White/Blue wire as necessary between in-line harness connector C256 and DLC. Retest system for normal operation. If voltage does not exist for both measurements, repair White/Blue wire as necessary between in-line harness connector C256 and PCM. Retest system for normal operation.
  6. Turn ignition switch to LOCK position. Disconnect in-line harness connector C256 (White). In-line harness connector C256 is located near PCM. See Figure. Measure resistance of White/Blue wire between DLC terminal No. 2 and in-line harness connector C256 terminal No. 6 (female side). See Figure and Fig 2 . If resistance is less than 5 ohms, repair open in White/Blue wire between in-line harness 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 harness connector C256 and DLC. Retest system for normal operation.
  7. Disconnect NGS tester. Disconnect PCM harness connector. PCM is located under center console. See Figure. Inspect PCM component and harness connectors for loose, damaged or corroded terminals. Pay particular attention to harness connector terminal No. 15 (Black/Blue wire). See Fig 1. Inspect DLC for loose, damaged or corroded terminals. Pay particular attention to terminal No. 10 (Black/Blue wire). See Figure. If connectors are okay, go to next step. If either connector is not okay, repair connector(s) as necessary and retest system for normal operation.
  8. Measure resistance of Black/Blue wire between DLC terminal No. 10 and PCM harness connector terminal No. 15. 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 switch to ON position. Measure voltage between DLC terminals No. 4 (Black wire) and No. 10 (Black/Blue wire) then measure voltage between DLC terminals No. 10 (Black/Blue wire) and No. 16 (Green wire). See Figure. If voltage exists for either measurement, go to next step. If voltage does not exist for both measurements, check powertrain control system operation. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
  10. Turn ignition switch to LOCK position. Disconnect in-line harness connector C256 (White). In-line harness connector C256 is located near PCM. See Figure. Turn ignition switch to ON position. Measure voltage between DLC terminals No. 4 (Black wire) and No. 10 (Black/Blue wire), then measure voltage between DLC terminals No. 10 (Black/Blue wire) and No. 16 (Green wire). If voltage exists for either measurement, repair Black/Blue wire as necessary between in-line harness connector C256 and DLC. Retest system for normal operation. If voltage does not exist for both measurements, repair Black/Blue wire as necessary between in-line harness connector C256 and PCM. Retest system for normal operation.
  11. Turn ignition switch to LOCK position. Disconnect in-line harness connector C256 (White). In-line harness connector C256 is located near PCM. See Figure. Measure resistance of Black/Blue wire between DLC terminal No. 10 and in-line harness connector C256 (female side). See Figure and Fig 2 . If resistance is less than 5 ohms, repair open in Black/Blue wire between in-line harness 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 harness connector C256 and DLC. Retest system for normal operation.
Fig 1: Identifying Powertrain Control Module Terminals
G97E28807Courtesy of FORD MOTOR CO.
Fig 2: Identifying In-Line Harness Connector C256 Terminals (Female Side)
G98F01709Courtesy of FORD MOTOR CO.
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