Part 2 in a 3 part, in diagnosing hard starting in cold weather. Last time we replaced the ignition switch, hoping that would do it. It was a temporary solution. We ran into a computer code showing that the crankshaft position sensor might also be the problem. But this trouble code came up about three weeks later and so I plugged in my scanner to the Trailblazer to be sure, then once I was sure that was the problem, I went on the hunt to locate it in the engine. It was a bugger to find! [Remember to disconnect your negative cable from your battery BEFORE starting this project because it is an electrical repair and on GM vehicles they require unhooking the negative cable on any repairs done.]
Once we found it we went and picked up the new part. Now the owner of this vehicle says she has looked it up on Youtube and other mechanics have suggested using a flexible shaft socket extension to get these bolts out because there are two. One for the sensor and one for the mount holding the bolt for the sensor. So we purchased the said extension. It was a 3/8 drive so we get back to the car and start doing the repair. They say you have to get to the sensor through the left front tire wheel housing. So we jacked up our left side and braced it with a jack stand
too. 
Now, when I got in there with my flex shaft extension, it started to bend and twist from the pressure that was put on it while trying to break the bolts. So whoever says those flex shaft socket extensions are the best way to get to these bolts are UP IN THE NIGHT!!! So I got in there with my vintage 2 inches long 3/8 drive socket extension and it did the job very well but I had to use a shallow socket on it but it still did the job!
Once the crankshaft position sensor was out I was able to unplug it from its clip. Now be careful with the clip on these. Have patience with it. It’s a little bit of a bugger to undo. Especially when you can only feel it and can’t see it and the short length of wire they have on it.
After getting the sensor out and unplugged it doesn’t look too bad. But if this is causing our trouble code we will replace it with the new one and hope this stops the service engine light from coming on and rid the Trailblazer of having a hard starting in cold weather.
Look at the pictures of the new versus the old crank sensors. The old sensor may have been the original sensor from the factory to this engine. By looking at it, it was greasy and it doesn’t look it had never been taken out before. 
Now installation is the reverse of removal of the sensor. Be sure to check your plug connection to the crank position sensor and it is clear of any debris and be sure the surface of the engine where to reinstall the mounting base of the sensor is clean and make sure the threads of the bolts are also clean so it will be a clean installation. So this will be a very successful and perfect repair.
Now, remember to reconnect your negative battery cable to the battery before starting your vehicle and checking for any trouble codes. If this doesn’t fix this problem the PCM will be our next item to look at.
