Rick's Free Auto Repair Advice

P0340 code — What the code means

Learn What A Camshaft Position Sensor Circuit Malfunction P0340 Code Means and How to Fix It

A P0340 code is defined as: Camshaft Position Sensor Circuit Malfunction. Unlike a P0344 intermittent circuit code, the P0340 is a constant circuit issue.

What the camshaft position sensor does

When car makers eliminated the distributor they needed a way to know the position of the camshaft so they could fire the spark plugs at the correct time. So the camshaft position sensor takes the place of the distributor and helps time the spark to the proper cylinder. When you see a P0340 code, the computer is telling you that it’s isn’t seeing the signal coming from the camshaft sensor.

Most common causes of a P0340 code

Faulty camshaft position sensor
Broken wire in the harness from the ECM to the sensor or corrosion in the electrical connector to the sensor
Chipped or missing teeth on the crankshaft tone ring

How to diagnose the problem with the camshaft position sensor signal

This image shows a typical camshaft position sensor

Typical camshaft position sensor

Always start by checking the condition of the wiring harness near the camshaft position sensor. Look for signs of chaffing, rub-through or cut wires. Next, disconnect the connector to the sensor and check for bent/loose pins or corrosion. Repair the problem if you find one.

Follow that up with voltage checks using a shop manual to locate the expected voltages.

Diagnosing the sensor itself for intermittent operation is difficult for DIYers because the best way to test is with a scope. If the wiring harness checks out, check the condition of the tone ring before replacing the sensor.

The sensor operates just like a wheel speed sensor where it monitors a tooted ring on the crankshaft. A chipped or missing tooth can cause a P0340 code.

© 2012 Rick Muscoplat

Posted on by Rick Muscoplat



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