Applicable Systems
PC200 Excavator
Symptoms
The engine speed sensor (pickup) signal is intermittent. The ECU logs a crankshaft position sensor fault, which may cause hard starting or rough running.
Possible Causes
- Speed sensor air gap too large due to sensor loosening or mounting bracket vibration
- Sensor pickup face contaminated with metal particles from clutch or flywheel wear
- Sensor wiring harness chafed or connector corroded from exposure
Troubleshooting Steps
- Step 1: Locate the speed sensor on the flywheel housing and check the air gap
Gap should be 0.8-1.2 mm; adjust if outside this range - Step 2: Remove the sensor and inspect the pickup face for contamination
Clean with a lint-free cloth; do not use magnetic tools that could attract debris - Step 3: Check the sensor wiring harness for chafing, especially near hot or moving parts
Repair or replace the harness section if damage is found - Step 4: Measure the sensor resistance with a multimeter
Inductive pickup should read 500-1500 ohms; replace if open or shorted
How to Reset
Reset: Clear the fault code using the diagnostic tool after the sensor signal stabilizes.
Common Replacement Parts
- Crankshaft speed sensor: Magnetic inductive type (Verify part number against engine serial)
- Sensor harness: Shielded 2-wire, 16 AWG (Check OEM harness repair kit)
Frequently Asked Questions
- Q: What is the correct speed sensor air gap?
Typically 0.8-1.2 mm (0.030-0.050 inch). Consult the manual for the specific engine model.
- Q: Can a bad speed sensor cause stalling?
Yes. The ECU relies on the speed signal for injection timing. Loss of signal can cause immediate engine shutdown.
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Source: OEM Service Manual
Category: Heavy Equipment
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