How To Test a Chevy Blazer Crank Sensor

When your Chevy Blazer crank sensor begins to fail, it can create a dangerous driving condition for your vehicle. If you own a Blazer with an automatic transmission, a failing crank sensor can cause your engine to shut off. Because the crank sensor informs your ECU of the crank position and crankshaft speed, your engine cannot run without this information.

This is why if you are seeing a crank sensor problem or OBDII check engine trouble code, you must take action quickly to test or replace your Blazer Crank Sensor. When your crank sensor is failing it can even cause a non start condition or cause your Blazer to have starting problems.

Today I’ll be showing you how to test a Blazer Crank Sensor in a 2003 Chevy truck. This truck is equipped with a 4.3 liter engine, and this how to can be applied to any 4.3, 5.0 or 5.7 liter Chevy engine of this era.

This crank sensor is connected by a three pin weatherproof connector. These three wires are made up of power, ground and the signal wires.

Before you can begin testing your Blazer Crank Sensor, you will need a multimeter to test the values at each wire. Because the crank sensor is located near your transmission bell housing, you can reach this from underneath your vehicle. If you aren’t sure what a multimeter is, or how to use a multimeter to read the DC voltage of a wire, check out our handy guide here.

How to test your Blazer Crank Sensor

Your sensor connector is made up of three pins, and you will need to test for power first. To do this you must insert the Blazer ignition key and turn the key to the “ON” position. With your key inserted and turned to the “ON” position, you will be powering the sensors in your engine bay.

To test the Blazer crank sensor for power and ground, you will need to use the diagram above and correspond it to the harness side. Once you’ve located the crank angle sensor on your Chevy we can begin.

Symptoms of a failing Blazer Crank Sensor

Many of the common symptoms of a bad crank sensor can range from your Blazer not starting or difficulty starting. This can also lead into you Chevy Blazer shutting off while driving or not starting at all. Of course because our test vehicle is made after 1996, there are also several OBDII check engine trouble codes that can arise from the failing sensor.

• P0336 CKP Sensor Circuit Performance
• P0337 CKP Sensor Circuit Low Frequency Code
• P0338 CKP Sensor Circuit High Frequency Code
• P0339 CKP Sensor Circuit Intermittent

These crankshaft angle sensor check engine trouble codes are just the beginning of your problems. Failing crank sensors can be very dangerous, especially if you own an automatic transmission equipped Blazer. If your engine stalls at speed, there’s no chance that you can restart it at speed without some serious risk or danger.

Testing the Blazer Crank Sensor for Power

To begin our how-to guide to testing your Blazer Crank sensor, you will begin checking for power and ground. This is done through your wiring harness, and keep in mind that you need the ignition key inserted and turned to the “ON” position.

The pin you will be testing is PIN 1, and this wire should be a 12 volt DC signal from your engine harness. This is the same whether you own a 4.3L, 5.0L or 5.7L equipped GM vehicle. If you have power at this wire, you can move onto checking for the low reference ground signal.

The ground wire is PIN 2, and if you have a ground signal here, that means your crank angle sensor should be working just fine. Chances are if your sensor is getting power and ground at these wires, your crank angle sensor in your Chevy has gone bad.

You can take one step further if you can trace the wiring harness back from PIN 3. If possible you should be able to tap into PIN 3 to check and see if there’s a 5 volt signal being sent when you crank your engine.

Never stay under the vehicle when you are cranking your engine, and you should skip this step unless you can trace back the wiring to a safe location. Do not attempt to test or check this wire from under the vehicle or near your crank angle sensor. If you have any questions check our guide on safety for working on your vehicle here.

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