DTC P1690: FUEL INJECTION PUMP CKP SENSOR DOES NOT AGREE WITH ECM CKP SENSOR

Monitor & Set Conditions

Fuel Injection Pump Crankshaft Position (CKP) circuit is monitored when ignition is on and engine is running. DTC may be stored when no signal exists within specified window parameters with no Camshaft Position (CMP) sensor or CKP DTCs present.

Possible Causes

• AC Noise Across Fuel Transfer Pump
• Other DTCs Present
• Wiring & Connectors
• Fuel Injection Pump Static Timing
• Fuel Sync Signal Circuit Open
• Fuel Sync Signal Circuit Short To Ground
• ECM

Testing

1. Measure AC noise to ECM by connecting DVOM between ground and terminals No. 48 and 50 (Red/White wires) at ECM harness connector. If AC voltage is 25 mV rms or less, go to next step. If AC voltage is greater than 25 mV rms, replace fuel transfer pump. See appropriate REMOVAL, OVERHAUL & INSTALLATION article.

2. Turn ignition on with engine off. Using DRBIII(R) scan tool, check for DTCs. If no additional DTCs exist, go to next step. If any additional DTCs exist, repair other DTCs first. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .

3. Using scan tool, check Good Trip Counter for DTC P1690. If Good Trip Counter for DTC P1690 is displayed and equal to zero, go to next step. If Good Trip Counter for DTC P1690 is displayed and not equal to zero, go to step 5 .

4. Turn ignition off. Disconnect FPCM harness connector. FPCM harness connector is located on end of fuel injection pump. Check for poor connection/terminal contact at FPCM harness connector. Repair as necessary. Disconnect ECM harness connector. ECM is located on driver's side of engine, just in front of fuel transfer pump and contains a 50-pin connector. Check for poor connection/terminal contact at ECM harness connector. Repair as necessary. Using DVOM, measure resistance of Dark Green wire between terminal No. 8 on FPCM harness connector and terminal No. 18 on ECM harness connector. If resistance is less than 5 ohms, go to step 7 . If resistance is 5 ohms or greater, repair open in Dark Green wire
between FPCM and ECM.

5. Turn ignition off. At this time, conditions required for DTC to be stored are not present. Inspect wiring and connectors between FPCM and ECM. FPCM is located on top of fuel injection pump. ECM is located on driver's side of engine, just in front of fuel transfer pump and contains a 50-pin connector. If no problems exist, go to next step. If any problems exist, repair wiring or connectors as necessary.

6. Check fuel injection pump timing. See CHECKING FUEL INJECTION PUMP TIMING under FUEL INJECTION PUMP TIMING in ON-VEHICLE ADJUSTMENTS - RAM PICKUP - DIESEL article. If fuel injection pump timing is okay, go to next step. If fuel injection pump timing requires adjustment,
adjust fuel injection pump timing as necessary.

7. Ensure ignition is off. Disconnect FPCM harness connector. FPCM harness connector is located on end of fuel injection pump. Disconnect ECM harness connector. ECM is located on driver's side of engine, just in front of fuel transfer pump and contains a 50-pin connector. Using DVOM, measure resistance between ground and terminal No. 8 (Dark Green wire) on FPCM harness connector. If resistance is 5 ohms or greater, replace and program ECM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. If resistance is less than 5 ohms, repair short to ground in Dark Green wire between FPCM and ECM.