How To Test The 24X Crank Sensor (GM 3.1L, 3.4L)

Testing the 24X crankshaft position sensor (located behind the crankshaft pulley/balancer) or code P0336 (24X Reference signal circuit) is an easy test that only involves a digital multimeter! You don't even need a scan tool (although a scan tool is a very handy tool to have).

The test that I'm going to show you is a dynamic test done by hand cranking the engine. If you're looking to do a resistance test of the 24X crank sensor, forget about it, such a resistance test for the 24X crank sensor does not exist.

The only way to test the 24X crank sensor is in action (as the engine is being manually cranked) and this article will show you how.

If you need to know if this 24X crank sensor test applies to your specific 3.1L or 3.4L GM vehicle, take a look at the ‘Applies To:’ box on the right and scroll with the arrow buttons to see all of the applications.

You can find this tutorial in Spanish here: Cómo Probar El Sensor Del Cigüeñal 24X (3.1L, 3.4L GM) (at: autotecnico-online.com).

Tools Needed To Test The 24X Crank Sensor

You don't need any expensive tools to test the crank sensor on your 3.1L or 3.4L V6 engine.

Tools You'll Need:

• Multimeter.
  • You can use a digital multimeter or an analog multimeter although the digital one is the preferred one.
  • 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: easyautodiagnostics.com).
• Jack
• Jack stands
• 1/2 inch ratchet wrench

Symptoms Of A Bad 24X Crank Sensor

The most obvious symptom of a bad crank sensor is the check engine light (CEL) lit nice and bright and the following diagnostic trouble code stored in the PCM's memory.

Below is a simple list of more specific symptoms that accompany a bad crank sensor:

• Bad 24X crankshaft position sensor diagnostic trouble code (DTC):
  • P0336 24X Reference Signal Circuit.
• Rough idle.
• Bad gas mileage.
• Won't pass the state emission's test (smog check).

The most important thing to remember, is that when the 24X crank sensor has failed, your car will still start and run (although it may not run great).

Where To Buy The 24X Crank Sensor And Save

There's a good chance that you can buy the original AC Delco 24X crank sensor online for a whole lot cheaper than somewhere local.

The following links will help you comparison shop for the factory original AC Delco (and aftermarket) 24X crank sensor:

Unsure if the above 24X crank sensor fits your particular vehicle? Don't worry, once you get to the site, they'll make sure it is by asking you the specifics of your vehicle. If the above don't fit, they'll find you the right one.

What Is A 24X Crank (CKP) Sensor?

Some late model 3.1L and all 3.4L GM V6 engines use two crankshaft position sensors.

One crank sensor is called the 3X (or 7X) crank sensor and this bad boy is:

• Located on the side of the engine block facing the firewall (passenger compartment).
• This crank sensor is a 2 wire type and produces an AC voltage signal.
• The signal that the 3X (7X) crank sensor produces goes directly to the ignition control module and is critical for it to start activating spark and fuel injection.

The other crank sensor (and the one this article will show you how to test) is the 24X crankshaft position sensor and:

• Is a Hall-Effect three wire crankshaft position sensor.
• As such, it produces an ON/OFF DC voltage signal that can be measured with a multimeter, an oscilloscope, and even an LED light.
• The crank sensor test in this article will focus on using a multimeter for the test.
• The signal that the 24X crank sensor produces goes directly to the Powertrain Control Module (PCM = Fuel Injection Computer) and is NOT critical for the activation of spark and fuel injection.

Now, in case you're wondering why it's called 24X, it's because it produces 24 evenly spaced ON/OFF signals for every one crankshaft revolution. These signals are what helps the PCM (Powertrain Control Module=Fuel Injection Computer) to better control idle (and a host of other things) at lower RPMs.

The most important thing to know, is that the 24X CKP will usually not keep the car or mini-van from starting if it goes bad.