Diagnostic Aids

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, CMP/TSS GND, PWR GND, SIG RTN & VPWR Wiring Harness Circuits
• Faulty Camshaft Position (CMP) Sensor
• Faulty Powertrain Control Module (PCM)

Fault Code	KOEO	KOER	Continuous Memory
P0340	DR1	DR1	DR1

1. 1) KOER & Continuous Memory DTC P0340: Check If Engine Will Start
   
   This DTC indicates PCM has detected a CMP sensor circuit fault. Possible causes for this fault are:
   • CMP Circuit Open Or Shorted To GND Or PWR
   • CMP GND Circuit Open (Hall Effect Type CMP Sensor)
   • SIG RTN Circuit Open (Variable Reluctance Type CMP Sensor)
   • CMP Incorrectly Installed (Hall Effect 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 NO START/NORMAL CRANKTEST under SYMPTOMS in TROUBLE SHOOTING - NO CODES - EEC-V - CNG & GASOLINE article.

2. 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 unable to be duplicated at this time. Go to TEST Z, step 1) . If DTC P0340 is present, go to next step (for Econoline and Pickup 4.2L) or step  5) (for all others).
3. 3) Check VPWR Voltage To CMP Sensor
   
   Turn ignition switch to OFF position. Disconnect CMP sensor harness connector, located at right front of engine. Turn ignition switch to ON position. Using a DVOM, measure voltage of VPWR circuit between CMP sensor harness connector terminal and negative battery terminal. See Fig 2. 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. 4) Check PWR GND To CMP Sensor
   
   Turn ignition switch to OFF position. Using a DVOM, measure resistance of PWR GND circuit between CMP sensor harness connector terminal and negative battery terminal. See Fig 2. 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. 5) Check CMP Sensor CMP, CMP GND/SIG RTN Or PWR GND Circuit For Open
   
   Disconnect PCM connector(s). Inspect connector for loose, damaged or corroded terminals. Disconnect CMP sensor connector. Using a DVOM, measure resistance of each CMP sensor circuit between PCM harness connector terminal and CMP sensor harness connector terminal. See Fig 1, Fig 3-Fig 8 . If all resistance measurements are less than 5 ohms, go to next step. If any resistance measurement is 5 ohms or more, repair open in affected circuit.
6. 6) Check CMP Circuit For Short To Power
   
   Reconnect CMP sensor. Turn ignition switch to ON position. On Econoline and Pickup 4.2L, measure voltage between PCM harness connector CMP and VPWR terminals. See Fig 2. On all other models, measure voltage between PCM harness connector CMP and CMP GND/SIG RTN terminals. See Fig 1, Fig 3-Fig 8 . If voltage is less than one volt, go to next step. If voltage is one volt or more, repair short to VPWR in CMP circuit.
7. 7) Check CMP Circuit For Short To GND Or SIG RTN
   
   Turn ignition switch to OFF position. Disconnect CMP sensor. On Econoline and Pickup 4.2L, measure resistance between PCM harness connector CMP and PWR GND terminals. See Fig 2. On all other models, measure resistance between PCM harness connector CMP and CMP GND/SIG RTN terminals. See Fig 1, Fig 3-Fig 8 . If all resistance measurements are more than 10 k/ohms, go to next step. If any resistance measurement is 10 k/ohms or less, repair short to ground or CMP GND/SIG RTN in CMP circuit.
8. 8) Check For Shorts In PCM
   
   Reconnect PCM harness connector(s). On Econoline and Pickup 4.2L, measure resistance between PCM harness connector CMP and VPWR terminals, and between CMP and PWR GND terminals. See Fig 2. On all other models, measure resistance between PCM harness connector CMP and CMP GND/SIG RTN terminals. See Fig 1, Fig 3-Fig 8 . If all resistance measurements are more than 500 ohms, go to step  10) (for Econoline and Pickup 4.2L) or next step (for all other models). If any resistance measurement is 500 ohms or less, replace PCM.
9. 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. Using a DVOM, 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. If AC voltage does not vary more than .1 volt, replace CMP sensor.
10. 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 - EXCEPT BI-FUEL 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.