How To Test The Cam Sensor Diagnostic Trouble Codes: P0340, P0341

Testing the cam sensor, inside the distributor on all 4.3L, 5.0L, and 5.7L GM equipped mini-vans, pick ups and SUVs, can be easily and accurately done with just a multimeter.

No scan tool required for the cam sensor test since a scan tool is not gonna' be much help. Aslo a resistance test of the cam sensor will get you no-where since the cam sensor is a Hall Effect type sensor that can not be Ohm-ed (resistance tested) with a multimeter.

I'm gonna' show you a way to do it with just a multimeter (in Volts DC mode) that is so accurate that you'll be able to say, ‘Yes, the cam sensor is BAD’ or ‘No, the cam sensor is OK’. And as you know this is a time and money saver.

This article will also help you to troubleshoot the following diagnostic trouble codes: P0340 (Camshaft Position (CMP) Sensor Circuit) and P0341 (Camshaft Position (CMP) Sensor Performance).

If you need to know if this camshaft position sensor test applies to your specific 4.3L, 5.0L, 5.7L GM mini-van, pick up or SUV, take a look at the ‘Applies To:’ box on the right and scroll with the next button to see all of the applications.

Tools Needed To Test The Cam Sensor

You don't need any expensive tools to test the cam sensor on your 4.3L, 5.0L, 5.7L engine.

Tools You'll Need:

  1. Multimeter.
    1. You can use a digital multimeter or an analog multimeter although the digital one is the preferred one.
    2. If you don't have a multimeter or need to upgrade yours, check out my recommendation here: Buying A Digital Multimeter For Automotive Diagnostic Testing (at:
  2. 1/2 inch ratchet wrench
  3. Socket that will fit crankshaft pulley bolt.
  4. A helper.

Symptoms Of A BAD Cam Sensor

When the cam sensor goes BAD, it will NOT keep your 4.3L, 5.0L, or 5.7L GM equipped vehicle from starting. Yep, that's right your mini-van or pick up or SUV will crank up and start. Now, of course, it's not gonna' run right.

Here are a couple of symptoms that your vehicle is probably experiencing:

  1. The check engine light will be on and the following codes may be stored in the PCM's memory:
    1. - P0340 Camshaft Position (CMP) Sensor Circuit.
    2. - P0341 Camshaft Position (CMP) Sensor Performance.
  2. Your GM mini-van, pick up, or SUV gas mileage is going thru' the roof (in a negative manner-o'-speaking that is).
  3. Your GM mini-van, pick up or SUV idles rough.
  4. Hard start (starts after an extended amount of cranking time).

The very first thing you need to ask yourself, before testing the cam sensor is: Did the codes (P0340, P0341) or the symptoms appear after I replaced or moved the distributor?.

If the answer is YES to the above question then you need to read the next section...

The Trouble Codes Appeared After Replacing The Distributor

In all of the years I've been working on cars (as an automotive tech), the number one cause of DTCs P0340 and/or P0341 has been that the distributor was removed and installed but not synchronized correctly.

If this is the case in your specific situation then you have found the solution to your problem (and diagnostic trouble codes).

You'll need to synchronize the timing marks on the distributor and the crankshaft pulley/ timing cover so that the rough idle, check engine light and trouble codes can go away.

You'll need to use a repair manual (or a Google Search) to find out how to install the distributor correctly since I don't cover any remove and replace info in this article.

If you haven't removed the distributor at all, then this article will help you since it sounds like the cam sensor is defective and I'll show you how to test it.