ASE A1 Engine RepairEngine Electrical Systems (General)Easy
A technician is diagnosing a vehicle with an illuminated 'Check Engine Light' and a Diagnostic Trouble Code (DTC) P0340, indicating a Camshaft Position (CMP) Sensor Circuit Malfunction. The engine cranks but does not start. Which of the following is the MOST likely cause?
- AA malfunctioning alternator.
- BA clogged fuel filter.
- CA faulty CMP sensor or its wiring.
- DA completely discharged battery.
Show answer & explanationAnswer & explanation
Correct answer: C. A faulty CMP sensor or its wiring.
DTC P0340 specifically points to a problem with the Camshaft Position sensor circuit. A faulty CMP sensor or its wiring would directly cause this code and prevent the engine from starting.
Why the other options are wrong
- A. A malfunctioning alternator would primarily affect the charging system and battery voltage, not directly cause a P0340 code or a crank-no-start unless the battery was completely dead, which would be a 'no crank' scenario.
- B. A clogged fuel filter would cause fuel delivery issues, potentially leading to a crank-no-start, but it would not trigger a P0340 code.
- D. A completely discharged battery would result in a 'no crank' condition, not a crank-no-start with a specific CMP sensor code.
CMP Sensor Function
The Camshaft Position (CMP) sensor monitors the position of the camshaft, providing information to the Powertrain Control Module (PCM) for fuel injection timing and ignition synchronization.
- Essential for engine starting and smooth operation.
- Generates a signal indicating camshaft rotation.
- A faulty sensor can cause no-start or rough running conditions.
Memory trick: P0340 means 'Problem with Camshaft, Oh no!'