Crankshaft Position - Camshaft Position Correlation (Bank 1 Sensor A)

What it means

The ECU has found that the crankshaft and the intake camshaft on bank 1 are out of their expected relationship. In plain terms, the engine's valve timing looks wrong. This is often caused by a stretched timing chain, a jumped belt or a faulty cam phaser.

Symptoms

• Check engine light on
• Rattle from the timing chain at start-up
• Hard starting
• Rough running and reduced power
• Possible stalling

Probable causes

Most likely first

1. 1Stretched timing chain or worn guides/tensioner
2. 2Timing belt jumped a tooth or installed wrong
3. 3Faulty cam phaser stuck out of position
4. 4Low oil level or sludged oil affecting the phaser
5. 5Faulty camshaft or crankshaft position sensor
6. 6Damaged reluctor ring (crank or cam)

How to diagnose it

Work through these in order before buying parts

1. 1Record the code and its freeze frame data (speed, load, temperature when it set), then clear it and see if it comes back.
2. 2Check oil level and condition.
3. 3Check the cam/crank correlation values on live data if your scan tool supports it.
4. 4Compare cam and crank signals on an oscilloscope against a known-good pattern.
5. 5Inspect timing marks and measure chain stretch (some engines need the timing cover removed).
6. 6Check for technical service bulletins (TSBs) or software updates for your make and model; some codes have known factory fixes.

Common fixes

• Replace the timing chain kit (chain, guides, tensioner)
• Re-time or replace the timing belt
• Replace the cam phaser
• Replace a faulty cam or crank sensor