Diagnostic Aids

This test is used to diagnose the following:

• Clean Tachometer Output (CTO) harness circuit.
• Faulty PCM.
• Faulty Transmission Control Module (TCM).

1. 1) Check RPM PID
   
   Turn ignition off. Connect New Generation Star (NGS) tester to DLC. Start engine. Using NGS tester, access RPM PID. Monitor RPM PID while varying engine speed. If RPM PID increases as accelerator pedal is depressed, go to next step. If RPM PID does not increase, fault may be ignition related. Go to TEST DR .
2. 2) Check RPM Wire To Instrument Cluster For Open Or Short
   
   Turn ignition off. Disconnect PCM and TCM harness connectors. Inspect harness connector for damage. Disconnect instrument cluster connector. Measure resistance of Clean Tachometer Output (CTO) circuit between PCM harness connector and instrument cluster connector. Measure resistance of CTO circuit between PCM harness connector and ground. See Figure, Fig 1 and Fig 2 . See CIRCUIT PIN IDENTIFICATION (PCM)  table. If resistance is less than 5 ohms between PCM connector and instrument cluster, and greater than 10 k/ohms between PCM connector and ground, replace PCM. If either resistance measurement is not as specified, repair open or short in circuit.
   Fig 1: Identifying Instrument Cluster Connector Terminals (CTO Circuit)

   Courtesy of FORD MOTOR CO.
   Fig 2: Identifying CTO Circuit & Test Pins

   Courtesy of FORD MOTOR CO.
   NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 2)  to step 10)  . No test procedures have been omitted.
3. 10) DTC P0725: RPM Signal To TCM Fault
   
   Start engine. Using NGS tester, select DIAGNOSTIC DATA LINK. Select TCM-TRANSMISSION CONTROL MODULE. Select PID/DATA MONITOR AND RECORD. Access ENG RPM. Read ENG RPM signal while pressing accelerator pedal slowly. If ENG RPM changes according to accelerator pedal position, replace transmission control module. If ENG RPM does not change according to accelerator pedal position, go to next step.
4. 11) Check CTO Circuit
   
   Turn ignition off. Disconnect TCM and PCM harness connectors. Measure CTO circuit resistance between TCM and PCM harness connectors. See Fig 2. See CIRCUIT PIN IDENTIFICATION (TCM)  table. See Figure. If resistance is less than 5 ohms between TCM connector and PCM harness connectors, and greater than 10 k/ohms between TCM connector and ground, replace TCM. If either resistance is not as specified, repair open or short in CTO circuit.