Caterpillar Fault Code
Free · no signupCA689
Engine Speed Sensor: Erratic Signal
System
Engine
Symptom
Engine Speed Sensor: Erratic Signal
Diagnosis & fix steps
LOGIC: Crank/Cam sensor skipping beats.
ACTION: Check sensor air gap and look for metal shavings on the magnetic tip.
Red Seal field insights
Shavings on the tip act as a "shield," causing the ECM to lose track of TDC.
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