ASE A1 Engine RepairEngine Electrical Systems (General)Medium
A vehicle owner complains that their check engine light is illuminated, and the engine occasionally stalls or runs rough at idle. Diagnostic Trouble Code (DTC) P0335 (Crankshaft Position Sensor 'A' Circuit Malfunction) is stored. The technician should FIRST check which of the following?
- AThe wiring and connector for the CKP sensor
- BThe fuel pressure at the rail
- CThe operation of the oxygen sensor
- DThe engine's compression
Show answer & explanationAnswer & explanation
Correct answer: A. The wiring and connector for the CKP sensor
DTC P0335 specifically indicates a problem with the Crankshaft Position (CKP) sensor circuit. The first diagnostic step for any circuit-related DTC is to inspect the wiring and connectors for damage, corrosion, or looseness.
Why the other options are wrong
- B. Fuel pressure is a fuel delivery issue, not the primary cause indicated by a CKP sensor circuit DTC.
- C. Oxygen sensor operation relates to exhaust gas analysis and fuel trim, not direct CKP sensor circuit issues.
- D. Engine compression is a mechanical issue not directly related to a CKP sensor circuit malfunction DTC.
CKP Sensor Diagnosis
The Crankshaft Position (CKP) sensor monitors engine speed and piston position, crucial for ignition timing and fuel injection. A circuit malfunction DTC points to electrical integrity.
- Provides engine speed and position data to the Powertrain Control Module (PCM).
- Essential for engine starting and smooth operation.
- DTC P0335 indicates a circuit issue with this sensor.
Memory trick: P0335: Crank Sensor's sigh, check the wires, then reach high.