Diagnostic Aids

NOTE: After each service or repair procedure has been completed, reconnect all components. Clear DTCs and repeat QUICK TEST procedures to ensure all EEC-V systems are working properly and DTCs are no longer present.

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 & VPWR Wiring Harness Circuits
Faulty Camshaft Position (CMP) Sensor
Faulty Powertrain Control Module (PCM)

NOTE: Proceed to DTC testing steps listed in FAULT CODE SETTING CONDITION table of fault code setting condition.

FAULT CODE SETTING CONDITION

Fault Code	KOEO	KOER	Continuous Memory
P0340		DR1	DR1

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, P0340 is not cause of no 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 switch to OFF position. 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 switch to OFF position. Disconnect CMP sensor connector, located at right front of engine. Turn ignition switch to ON position. Measure voltage between VPWR terminal at CMP sensor harness connector and negative battery terminal. See Fig 8. 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 switch to OFF position. Measure resistance between PWR GND circuit at CMP sensor 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 connector(s). 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 harness connector. See Fig 1-Fig 9 . 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 switch to ON position. On LS, measure voltage between PCM connector terminals No. C53 and A24, A25, A26 and A27. On all other models, measure voltage between PCM connector terminals 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 switch to OFF position. Disconnect scan tool from Data Link Connector (DLC). On Pickup 4.2L, measure resistance between PCM connector terminal No. 85 and terminal No. 24 (PWR GND). On LS, measure resistance between PCM connector terminal C53 and terminal C17 (SIG RTN). On all other models, measure resistance between PCM connector terminal No. 85 and terminals No. 103 (PWR GND) and 91 (SIG RTN). If all resistance readings are more than 10 k/ohms, go to next step. If any resistance reading is 10 k/ohms or less, repair short to ground or SIG RTN in CMP circuit.

8) Check For Short In PCM

Reconnect PCM connector. On Pickup 4.2L, measure resistance between PCM connector terminal No. 85 and terminals No. 71 and 24. On LS, measure resistance between PCM connector terminal C53 and terminal C17. On all other models, measure resistance between PCM connector terminal No. 85 and terminal No. 76. If all 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. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Program PCM. See FLASH VEHICLE IDENTIFICATION BLOCK PROCEDURE .

9) Check CMP Sensor Output

Turn ignition switch to OFF position. Reconnect CMP sensor harness connector. Set DVOM on AC scale to monitor less than 5 volts. Start engine. Measure voltage between PCM harness connector CMP and CMP GND/SIG terminals while varying engine speed. If AC voltage varies more than .1 volt, replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Program PCM. See FLASH VEHICLE IDENTIFICATION BLOCK PROCEDURE . If AC voltage does not vary more than .1 volt, replace CMP sensor.

10) Check CMP Sensor Output During Cranking

Turn ignition switch to OFF position. Disconnect PCM connector(s). Ensure CMP sensor is installed properly and reconnected. Connect DVOM between PCM harness connector CMP and PWR GND terminals. Set DVOM on DC scale. Using starter, crank engine (DO NOT allow engine to start) in short bursts for at least 10 engine revolutions.
If voltage does not switch from less than 2 volts to more than 8 volts, replace CMP sensor. If voltage switches from less than 2 volts to more than 8 volts, ensure Hall Effect type CMP sensor is installed correctly and synchronized. See CAMSHAFT POSITION (CMP) SENSOR under FUEL SYSTEMS (GASOLINE ENGINES) in REMOVAL, OVERHAUL & INSTALLATION - TRUCKS article. If CMP sensor is installed correctly and synchronized, replace PCM.

NOTE: If engine has a miss and DTC P0340 is present, ignition, alternator noise, Radio Frequency Interference (RFI) and/or Crankshaft Position (CKP) sensor problems should be considered.