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

What it means

The engine computer (ECU) has detected an electrical problem in the camshaft position (CMP) sensor A (bank 1) circuit. The camshaft position (CMP) sensor A (bank 1) tells the ECU the camshaft position so it can time fuel injection and variable valve timing. The signal is missing or outside the range the ECU will accept.

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. 1Damaged or unplugged connector
2. 2Open or shorted wiring
3. 3Failed sensor
4. 4Damaged reluctor (tone) ring

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. 4Check the sensor resistance (for 2-wire sensors) or power and ground (for 3-wire Hall-effect sensors). Watch the signal on an oscilloscope or graphing meter while cranking or driving; it should be a clean, regular pattern.
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

• Repair the damaged wiring or connector
• Replace the camshaft position (CMP) sensor A (bank 1)
• Clear the code and test drive to confirm the repair