Crank Position Sensor

What is the Crank Position Sensor?

The Crankshaft Position Sensor CKP https://amzn.to/3R4RQEK is a crankshaft reluctor wheel triggered hall effect sensor that allows the computer to know the speed and position of the crankshaft in it's rotation.  This is required for proper injector timing for engines with sequential fuel injection systems and helps the computer know if the engine is misfiring.

The most common symptom that is first noticed with a faulty CKP is that the engine won't start or will start hard.  Usually it will set a DTC, sometimes this happens right away, sometimes it takes a LOT of cranking before the DTC sets.  As always a DTC doesn't always mean that the sensor is bad, it could be the wiring/connectors/grounds/power/etc as well.  This is why diagnostics are important.  You can also have issues with a rough idle, stalling, misfires, backfiring, etc.

One quick way to test if the sensor and wiring are working at all is to pull the sensor, check for wear marks on the front of the sensor, and bring it close and farther away from a steel object like the sub-frame on the A/S vans, you should hear the fuel pump turn on if the sensor/wiring/etc is functioning properly.

Here are a few things to keep in mind:

1. Make sure to check the wiring and connectors when replacing the CKPS

2. As the crankshaft bearings wear, it can cause an issue with the reluctor being too close or actually hitting the CKPS, this can also happen with a replacement sensor.  You must have at least a 0.030" air gap between the sensor and the reluctor wheel, this can be checked with the proper gauging compound.

3. Always do a CKP System Variation Learn procedure using a proper scan tool when you replace the sensor/engine/timing cover/PCM/balancer/shims/etc.

4. When replacing the sensor, the sensor tip and reluctor should never touch, sometimes the sensor will require 1 or 2 0.5mm thick shims GM 12565102 (check dealer) or https://amzn.to/3KxQsrS and might cause false misfire detection or DTCs to be set if there is not enough space between the two.  You could also make your own cut from an aluminum can. TSB #02-06-04-059  Some replacement sensors come with a pack of shims included.

5. Replace and lube the o-ring when the sensor is removed, torque is 8Nm or 71 lbin.

How do you do the CKP System Variation Learn procedure?

1. Connect the proper scan tool, only the Tech2 or other high end scanners have this option.

2. Within the scan tool, select the crankshaft position variation learn procedure.  Which includes stepping on the brake and going to specified RPM.

3. Follow directions on the scan tool.

Where is the CKPS located?

It's located on the bottom passenger side of the timing chain cover.  Lay under your van and and look up, you will see the crankshaft pulley with the belt on it, and right behind that on the plastic cover will be the crankshaft position sensor.  You can see pictures of the cover and pulley on the Distributor page.