Diagnostic Aids
WARNING: This page does not describe the selected car, but rather 26 other vehicles, including the 1999 Mercury Tracer, 1999 Mercury Sable, 1999 Mercury Mystique, 1999 Mercury Mountaineer, and 1999 Mercury Grand Marquis. However, it is still accessible from the selected car via links, so may be relevant.
CMP signal provides PCM information for fuel injector synchronization. The CMP signal originates from Camshaft Position (CMP) sensor.
Enter this system test only when instructed during QUICK TEST. This test is only intended to diagnose the following:
- CMP, PWR GND, SIG RTN and VPWR wiring harness circuits.
- Faulty Camshaft Position (CMP) sensor.
- Faulty Powertrain Control Module (PCM).
- 1) DTC P0340
This DTC indicates PCM has detected a CMP sensor circuit fault. Possible causes for this fault are:- CMP circuit open or shorted wiring harness.
- PWR GND or VPWR circuit open (Hall Effect type CMP sensor).
- SIG RTN circuit open (Variable Reluctance type CMP sensor).
- Faulty CMP sensor.
- Faulty PCM.
Attempt to start engine. If engine starts, go to next step. If engine does not start, go to TEST A .
- 2) Attempt To Re-Generate DTC P0340
Clear PCM memory. Start engine. Raise engine speed to 1500 RPM for 10 seconds. Return to idle speed. Raise engine speed to 1500 RPM for 10 seconds again. Turn ignition off. Perform QUICK TEST to retrieve Continuous Memory DTCs. If DTC P0340 is not present, fault is intermittent. Go to TEST Z . If DTC P0340 is present, go to next step (Pickup 4.2L) or step 5) (all other models). - 3) Check VPWR Circuit Voltage
Turn ignition off. Disconnect CMP sensor connector, located at right front of engine. Turn ignition on. Measure voltage between VPWR terminal at CMP sensor wiring harness connector and negative battery terminal. See Fig 4. If voltage is more than 10.5 volts, go to next step. If voltage is 10.5 volts or less, repair open in VREF circuit. - 4) Check PWR GND To CMP Sensor
Turn ignition off. Measure resistance between PWR GND circuit at CMP sensor wiring harness connector and negative battery terminal. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in PWR GND circuit. - 5) Check For Open CMP Sensor Circuit
Disconnect PCM 104-pin connector. Inspect connector for loose, damaged or corroded terminals. Disconnect CMP sensor connector. Measure resistance of each CMP sensor circuit between PCM connector and CMP sensor wiring harness connector. See Fig 1- Fig 5 . If all resistance readings are less than 5 ohms, go to next step. If any resistance reading is 5 ohms or more, repair open circuit. - 6) Check CMP Circuit For Short To Power
Ensure CMP sensor is disconnected. Turn ignition on. Measure voltage between PCM connector pins No. 85 and 103 (PWR GND). If voltage is less one volt, go to next step. If voltage is one volt or more, repair CMP circuit short to power. - 7) Check CMP Circuit For Short To Ground
Turn ignition off. Disconnect scan tool Data Link Connector (DLC). Measure resistance between PCM connector pin No. 85 and pins No. 103 (PWR GND) and 91 (SIG RTN). If all resistance readings are more than 10,000 ohms, go to next step. If any resistance reading is 10,000 ohms or less, repair short to ground or SIG RTN in CMP circuit. - 8) Check For Short In PCM
Reconnect PCM connector. Measure resistance between PCM connector pin No. 85 and pins No. 71 and 103. If both resistance readings are more than 500 ohms, go to step 10 (Pickup 4.2L) or next step (all other models). If any resistance reading is 500 ohms or less, replace PCM. - 9) Check CMP Sensor Output
Turn ignition off. Reconnect CMP sensor connector. Set DVOM on AC scale to monitor less than 5 volts. Start engine. Measure voltage between PCM connector pins No. 85 and 103 while varying engine speed. If voltage varies more than 0.1 volt, replace PCM. If voltage does not vary more than 0.1 volt, replace CMP sensor. - 10) Check CMP Sensor Voltage Output
Turn ignition off. Disconnect PCM connector. Ensure CMP sensor is installed properly. Connect DVOM between PCM connector pins No. 85 and 103. Using starter, bump engine (DO NOT allow engine to start) for at least 10 engine revolutions. If voltage switches from less than 2 volts to more than 8 volts, replace PCM. If voltage does not switch from less than 2 volts to more than 8 volts, replace CMP sensor.
Fig 1: identifying CMP Circuits & Connector Terminals (Contour 2.0L, Cougar 2.0L, Escort ZX2 & Mystique 2.0L)