Camshaft Position Sensor 'A' Circuit Malfunction

The cam sensor tells the PCM which stroke each cylinder is on so it can fire the right injector and coil at the right time. Without it, sequential injection and coil-on-plug timing fall apart. Many engines will still run (in a limp/batch fire mode) without the cam signal — just rough and with poor economy. P0340 means the signal is missing or out of sync with the crank.

No CMP pulses during cranking, OR CMP-to-CKP correlation is wrong (jumped tooth indication).

Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.

1. 1Scope CMP and CKP together. Look for both presence AND correct phase.
2. 2If CMP signal is fine but P0340 returns — suspect cam timing has jumped.
3. 3Pull valve cover if needed and verify timing marks at TDC #1.
4. 4Inspect connector and wiring.

• Failed cam sensor
• Wiring / connector fault
• Timing chain jumped a tooth (sensor is reading correctly but timing IS off)
• Damaged tone ring on the cam
• Bad VVT phaser causing wild cam position

$120 (sensor) to $2,500 (timing chain).