Pontiac Firebird P0340: CPS – Circuit Malfunction

P0340 is a somewhat common and difficult trouble code to diagnose. The Pontiac Firebird is no exception to this rule. That’s because it’s a generic powertrain code. Generic codes tell you that there is a problem, but they don’t really tell you what particular part of the system is throwing the code.


Pontiac Firebird P0340 Diagnosis


OBDII P0340 means that there is a problem with the Camshaft Position Sensor (CPS) circuit. While it can be tempting to throw a new camshaft position sensor in and see if it fixes the problem, the CPS doesn’t always end up fixing the problem. Since the CPS can often be difficult to get to, testing the wiring going to it makes good sense for step one.

Below, we’ll go over the symptoms and potential causes of P0340 in your Pontiac Firebird.


P0340 Symptoms: Pontiac Firebird

The CPS helps an engine determine optimal timing for combustion. When it is not functioning properly, it can cause a lot of drivability problems in your Firebird

They include:

  • Failure to Start
  • Poor Idle Quality
  • Decreased Fuel Economy
  • Drop in Engine Power


Pontiac Firebird P0340 Causes

P0340 Pontiac Firebird

As stated above, the P0340 code is often caused by a failure in the Camshaft Position Sensor itself. Here are the most common causes:

  • Wiring Issue– The Camshaft Position Sensor wiring is exposed to harsher conditions than a lot of the wiring in your Firebird. It is worth looking at it to see if it has developed a short, or to see if the harness connector is loose or damaged. Here’s a great article on how to diagnose a short in a car. It’s really not complicated once you get the hang of it.
  • Camshaft Position Sensor Failure– After examining all of the wiring around the CPS, it’s going to be time to test the sensor itself. Here is a fantastic video on how to do that with a multimeter.

There are significantly less likely causes for P0340 as well. These include the PCM failing or the Crank Sensor failing. You’ll need to check the voltage at the camshaft sensor to see if it is within spec.



P0340 is a serious concern and should be addressed as soon as possible. We recommend taking your Firebird into a mechanic as soon as possible. If you have any suggestions for improving this article, please feel free to leave a comment below. Good luck!