You can test the crankshaft position (CKP) sensor with either a multimeter resistance test or a multimeter performance test.
In this tutorial, I'll explain how to do both tests so that you can find out if the crankshaft position sensor is good or bad.
Contents of this tutorial:
APPLIES TO: This tutorial applies to the following vehicles:
- 4.2L Chevrolet TrailBlazer: 2002, 2003, 2004, 2005, 2006, 2007.
- 4.2L GMC Envoy: 2002, 2003, 2004, 2005, 2006, 2007.
WIRING DIAGRAMS:
Symptoms Of A Bad CKP Sensor
When the crankshaft position sensor fails, it'll usually cause the engine not to start.
You'll also generally see a CKP diagnostic trouble code registered in the PCM's memory and the check engine light illuminated on your Chevrolet Trailblazer or GMC Envoy's instrument panel.
If you do have the check engine illuminated by a CKP sensor diagnostic trouble code, you'll see:
- P0335: Crankshaft Position (CKP) Sensor Circuit Failure.
- P1335: Crankshaft Position (CKP) Sensor Circuit Failure With The Engine Running.
In some cases, the CKP sensor will fail intermittently. In other words, it'll work fine most of the time, but then it won't.
If your 4.2L Chevrolet TrailBlazer (GMC Envoy) is experiencing an intermittent no-start problem, you'll need to test the CKP sensor when the engine is not starting. Otherwise, the CKP sensor will always test good.
Where To Buy A CKP Sensor And Save
The crankshaft position (CKP) sensor isn't an expensive component. Still, it's important you avoid buying a knock-off sensor. Here are my recommendations of known automotive brands:
Important 4.2L CKP Sensor Testing Suggestions
The CKP sensor on your 4.2L Chevrolet TrailBlazer (GMC Envoy) is located next to the starter motor.
Its location, which I think you'll agree isn't the most accessible part of the engine, complicates getting to it and testing it.
The three options, ranked from easiest to hardest, you have when diagnosing the CKP sensor are:
- Just replace it.
- Remove it and bench test it.
- On-car CKP sensor's performance test.
OPTION 1: Replacing the CKP sensor without testing it to see if the problem goes away seems to be the de facto way of diagnosing the CKP sensor for many. For most folks, this makes sense for two simple reasons:
- The CKP sensor is not an expensive component.
- The CKP sensor is in an inaccessible testing location.
OPTION 2: If you need to make sure the CKP is bad (before replacing it), the quickest and easiest way to find out is to remove it and bench-test it. TEST 1 explains how to do this in detail.
This method still has its possible complications because the CKP sensor or its rubber seal may get damaged/destroyed when removing it. If this happens, you'll need to replace the CKP sensor even if it tests good.
OPTION 3: The on-car performance test of the CKP sensor is a bit more involved. In a nutshell, you would have to:
- Buy a CKP sensor pigtail connector (online or at your local auto parts store).
- Connect the pigtail connector to the CKP sensor.
- Connect your multimeter to this pigtail connector.
- Crank the engine.
- See if the multimeter reports an AC voltage.
In TEST 2, you'll find the on-car performance test of the CKP sensor described in detail.
TEST 1: Checking CKP Sensor Resistance With A Multimeter
OK, in this test section, we'll resistance-test the CKP sensor with a multimeter in Ohms mode.
Since it's pretty challenging to perform a resistance test on the CKP sensor on the vehicle, I'm gonna recommend that you remove it to bench test it.
The CKP sensor's resistance specification is 500 to 900 Ohms.
IMPORTANT: You'll need to raise your vehicle and place it on jack stands to access the CKP sensor. Don't trust the jack alone to keep the vehicle up in the air while you work underneath it.
Let's get started:
- 1
Disconnect the CKP sensor from its electrical connector.
LOCATION: The CKP sensor is located next to the starter motor. - 2
Remove the CKP sensor.
- 3
Place your multimeter in Ohms mode.
- 4
With your multimeter test leads, probe the male spade terminals of the CKP sensor.
- 5
You should see a resistance of 500 to 900 Ohms.
Let's analyze your test result:
CASE 1: The CKP sensor's resistance is within specification. This is the correct and expected test result and it tells you that the CKP sensor is OK.
Although not necessary, you can further confirm the CKP sensor is good by performing TEST 2. Go to: TEST 2: Testing The CKP Sensor's Output With A Multimeter.
CASE 2: The CKP sensor's resistance IS NOT within specification. This test result confirms that the crankshaft position sensor is bad and needs replacement.
Although not necessary, you can further confirm the CKP sensor is bad by performing TEST 2. Go to: TEST 2: Testing The CKP Sensor's Output With A Multimeter.
