Camshaft Position Sensor "A" Circuit Range/Performance (Bank 1 or Single Sensor)

What it means

The camshaft position (CMP) sensor A (bank 1) is sending a signal that is electrically valid but does not make sense compared with other sensors. The camshaft position (CMP) sensor A (bank 1) tells the ECU the camshaft position so it can time fuel injection and variable valve timing. This usually points to a sensor that is reading wrong, or to a real mechanical problem it is reporting correctly, rather than a broken wire.

Symptoms

• Check engine light on
• Hard starting or long cranking
• Stalling
• Rough running or reduced power
• Poor fuel economy

Probable causes

Most likely first

1. 1Stretched timing chain or jumped timing belt
2. 2Damaged camshaft reluctor
3. 3Oil leaking into the sensor connector
4. 4Failing sensor giving an inaccurate reading
5. 5Poor connection at the sensor connector

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. 2Inspect the camshaft position (CMP) sensor A (bank 1) connector and wiring (on the cylinder head or timing cover, at the end of a camshaft). Look for corrosion, bent or pushed-back pins, oil contamination and chafed insulation.
3. 3Watch the camshaft position (CMP) sensor A (bank 1) reading on live data. Use a scan tool or oscilloscope to check for a regular cam signal while cranking, and compare cam/crank correlation values if your tool shows them.
4. 4Compare the camshaft position (CMP) sensor A (bank 1) reading against related sensors and the real-world condition. If they disagree, find out which one is telling the truth before buying parts.
5. 5If the wiring checks out, test the sensor itself against the specification in a service manual.
6. 6Check for technical service bulletins (TSBs) or software updates for your make and model; some codes have known factory fixes.

Common fixes

• Fix the underlying problem the sensor is reporting, if real
• Replace the camshaft position (CMP) sensor A (bank 1) if it reads wrong against a known-good reference