Fuel Injection Pump CKP Sensor Does Not Agree With ECM CKP (Dodge)
What does P1690 mean?
The P1690 code means the vehicle's onboard diagnostic system has detected: Fuel Injection Pump CKP Sensor Does Not Agree With ECM CKP (Dodge). This is a moderate severity code.
Common Symptoms
- Check Engine Light on
- Rough running or misfires
- Hard starting
- Reduced engine power
- Engine timing feels off
Probable Causes (Ranked by Likelihood)
- Faulty crankshaft position sensor Very High
- Damaged CKP sensor reluctor ring High
- Injection pump timing off Moderate
- Worn timing gears causing signal mismatch Low
Step-by-Step Diagnostic Procedure
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Compare the CKP signal from the ECM and the injection pump CKP using a dual-channel oscilloscope.
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Inspect the main crankshaft position sensor for damage, debris, or excessive air gap.
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Check the injection pump timing using a scan tool to read injection timing values.
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Inspect the reluctor ring for missing teeth, cracks, or wobble.
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If both sensors read correctly individually, check for timing gear wear causing signal phase shift.
Frequently Asked Questions
Can I drive with P1690?
Short distances only. The timing mismatch can cause rough running and reduced power. Extended driving with incorrect timing can damage the engine.
Are there two CKP sensors on the Cummins diesel?
Effectively yes. The ECM uses one CKP signal and the VP44 injection pump has its own internal timing reference. P1690 sets when these two signals disagree.
Could a loose CKP sensor cause this?
Yes. If the sensor has backed out of its mounting, the air gap increases and the signal becomes unreliable, causing a disagreement between the two references.