🚨 Diagnostic Profile
Vehicle Make: CHRYSLER
Description: Fuel Injection Pump CKP Sensor Does Not Agree With ECM CKP Sensor. The crankshaft position signal reported by the fuel injection pump does not match the signal the ECM expects, which can cause hard starting, stalling, rough running, or a no-start condition.
🚨 Repair Difficulty Tier
Tier: [Intermediate]
Diagnosis requires scan tool access, electrical testing, and timing verification. Replacement of the sensor itself is straightforward, but confirming the root cause (wiring, sensor, reluctor alignment, or pump timing) requires a trained technician.
🛠️ Resolution Steps
Step 1: Preliminary Inspection
- Review the vehicle service history and any recent repairs involving the fuel system, timing components, or engine electrical work.
- Scan all modules (ECM/PCM and the fuel injection pump driver module) for stored and pending DTCs, and record freeze frame data before clearing anything.
- Visually inspect the CKP sensor connector and harness at the engine block/bell housing area near the crankshaft reluctor, as well as the connector at the fuel injection pump control module, for corrosion, pushed-back terminals, chafing from engine heat or vibration, or oil contamination.
- Inspect the CKP sensor mounting, air gap, and sensor body for cracks, debris, or metal shavings that could be drawn to the sensor tip magnetically.
- Check the reluctor or tone ring (on the crankshaft or pump drive gear, depending on system architecture) for damaged, missing, or loose teeth.
- Verify battery voltage and ground integrity to the ECM and fuel injection pump module using a digital multimeter against a known good chassis/engine ground; confirm minimum cranking voltage is maintained and that ground circuits show less than 0.2V drop under load.
Step 2: Diagnostic Verification
- Use a scan tool capable of bidirectional communication with both the ECM and the fuel injection pump control module to compare live CKP signal data (RPM value, signal presence, and sync status) from each module side-by-side at idle, during cranking, and under throttle transition.
- Measure CKP sensor signal output with a lab scope or multimeter. For magnetic (inductive) sensors, verify an AC voltage waveform that increases in amplitude and frequency proportionally with engine RPM; for Hall-effect sensors, verify a clean digital square-wave switching between a low and high reference voltage with no dropouts. Compare the waveform quality and signal timing as seen by the ECM versus the signal arriving at the pump control module.
- Check sensor resistance and continuity against the OEM factory service manual specification for the specific sensor type installed (inductive sensors typically read in the hundreds to low thousands of ohms; Hall-effect sensors cannot be resistance tested and require powered voltage testing instead).
- Check the harness for opens, shorts to ground, or shorts to voltage between the sensor, ECM, and pump connectors using the OEM factory wiring diagram for this specific VIN/engine combination, verifying continuity end-to-end and isolating any splice points shared between the ECM and injection pump circuits.
- Verify engine timing and injection pump timing alignment against the service specification, including checking for any timing belt/chain jump, reluctor wheel slippage, or incorrect pump-to-engine timing mark alignment if the pump was recently serviced or replaced.
- Confirm whether the fault is present on a warm and a cold engine, since sensor faults and harness chafing can be temperature and heat-cycle dependent, and intermittent faults often only surface after the engine reaches full operating temperature.
Step 3: Resolution & Reset Process
- Repair any damaged wiring, connectors, or grounds, and clean all terminals with approved electrical contact cleaner; use OEM-spec splice and heat-shrink techniques, never butt connectors, in any circuit shared with the ECM or injection pump module.
- If the sensor fails specification or shows erratic waveform behavior, replace it with an OEM or OEM-equivalent part and set the air gap to the factory specification using a non-ferrous feeler gauge where the design requires manual gap adjustment.
- If the reluctor or tone ring is damaged, replace it and verify runout and tooth alignment per factory specification before final reassembly.
- If timing is out of specification, correct engine and/or injection pump timing per the OEM procedure and re-verify CKP signal agreement before proceeding further.
- Clear all DTCs from both the ECM and the fuel injection pump module, perform any required crankshaft position relearn, injection pump timing relearn, or module reprogramming/flash update per the latest OEM service bulletin for this condition, and confirm the ECM and pump CKP signals now agree in live data.
- Road test the vehicle under varied load, RPM, and temperature conditions, then recheck for stored or pending codes to confirm the repair has resolved the fault and did not reintroduce a sync error.
📦 Parts, Labor, and Budget Estimates
Required Components/Software:
- CKP sensor: OEM Mopar/Chrysler part number specific to engine and model year (verify via dealer parts lookup or OEM catalog using VIN)
- Reluctor or tone ring (if damaged): OEM part specific to engine family; often sold only as part of the crankshaft, flywheel/flexplate, or pump drive assembly
- Wiring harness repair kit or connector terminals (if needed): OEM pigtail/connector repair kit or universal weatherproof terminal repair kit matched to connector family
- Timing or pump service components (if needed): OEM timing kit, pump drive gear, or keyway hardware as applicable to the diesel injection system
- Scan tool software or module reprogramming file (if required): Current OEM dealer diagnostic software subscription (e.g., factory scan tool software) for ECM/injection pump module flash and relearn procedures
Average Component Price:
- CKP sensor: approximately $40–$150 (part only)
- Reluctor or tone ring: approximately $80–$400 depending on whether it is sold separately or only as part of a larger assembly
- Harness or connector repair: approximately $25–$150 for repair kit/pigtail, more if a full harness section requires replacement
- Timing or pump service components: approximately $100–$600+ depending on diesel fuel system complexity and whether pump removal/timing hardware is required
- Diagnostic and software fees: approximately $120–$250 for initial diagnostic scan/testing, plus $100–$200 in dealer reprogramming or module relearn fees if required
Estimated Labor Hours:
- Diagnosis and verification: 1.0–2.5 hours
- CKP sensor replacement: 0.5–1.5 hours depending on sensor accessibility
- Harness repair (if required): 0.5–2.0 hours depending on extent of damage and location
- Timing verification or correction (if required): 1.0–3.0+ hours depending on whether injection pump timing must be reset or pump removed
- Reset, relearn, and road test: 0.3–1.0 hour