Car not starting - Replaced CPS

So I have had what I thought were the classic crank position sensor failure symptoms. Over the last 3 months the tach has intermittently dropped to zero and the Trac Off light comes on. The car stalled a few times while driving (normally at low speed) and became increasingly hard to start until a few days ago when I couldn't ever get it started. The engine turns over fine and I can hear the fuel pump kick on and also get gas coming out of the pressure release valve when I press it. I haven't pulled spark plugs yet for fear of destroying the plug wires in the process but that might be happening soon.

I replaced the crank position sensor last night and had no luck. Car still doesn't start. Do I need to reset the PCM after installing the new sensor? Could this be part of the problem? I am also wondering if I maybe have a broken wire going to the CPS sensor. I want to check continuity on the wires, but don't have a wiring diagram (if you have a diagram and could help me out I would be extremely grateful). Is there anything else I should be looking at? Any suggestions are greatly appreciated.

Thanks,

Ryan


1998 Grand Prix GT 3800
~95k miles

Maybe its just a bad module?

As in maybe the new CPS is bad? Or are you talking about the ignition module? Or maybe something I'm not aware of yet?

Welcome to AF.

What brand CPS did you install?

I replaced my CPS on my GTP at approx 80k. I used a new delco one from the dealer. I got everything back together and the car would not start. I ended up disconnecting the battery, removing the crank pully, checking my work, and putting the crank pulley back on when I didn't find anything wrong. When I finsihed, I hooked the battery back up and the car started this time around.

Maybe disconnectg your battery for 10 minutes and then try it. It might need to re-learn the new sensor.

Yeah I used the BWD brand from Advance Auto parts. I noticed the connector was extremely difficult to plug in and the fit seemed different than the stock sensor. I just ordered an AC Delco sensor and I will try that tonight. I'll post an update when I have some news. Thanks to everyone for your help so far.

I have found and fixed the problem. When I took the BWD brand sensor out I saw that one of the pins was bent out of shape and presumably not making contact with the plug. My guess is it was slightly misaligned to start with and I bent it further when pressing the plug on. The plug fortunately was unharmed. I popped in the AC Delco and everything fit like a glove and car runs great again. So I guess like everyone told me use a quality replacement . . . I learned the hard way. Thanks for the help.

Ryan

i have a 99 GP SE 3.8. i need to replace the CPS on my car. do you have a write up on how to replace it or know where i can get one. the link in the tips and maint does not work.

I wasn't able to find a good write up either. Here are the basic steps. (sorry no pictures)

1. Remove serpentine belt

2. Jack up front right and remove wheel

3. Remove black plastic cover that separates the wheel well from the engine compartment. It's not the wheel well lining. It's another cover that starts around the oil filter and goes forward.

4. After removing the cover you have access to the crank pulley bolt. I used the starter trick to loosen it and that worked like a charm. Place breaker bar/ratchet on the crank bolt and position the arm so that it rests on the frame towards the front of the car. Go turn the ignition in very short spurts 1 to 3 times just to crack the bolt free.

5. Disconnect the battery (just for safety)

6. Remove crank pulley bolt. (Should come out easily after cracked loose)

7. Use a large gear puller to remove the crank pulley. (Alternatively, you can use a harmonic balancer puller. The pulley has 3 threaded holes in it that I believe are 1/4"-28 thread. You can get a couple of 1/4-28 bolts to use in conjunction with the harmonic balancer puller to get the job done.)

9. Disconnect CPS plug.

8. Remove plastic housing that sat behind the crank pulley. (Can be stubborn, but it does just pop off so try to pull or pry in a few different areas)

9. Unbolt bolt the old CPS and lift/pry straight off. (The dowel pin going into the backside of the sensor can make it a little stubborn)

10. Replace with new CPS

11. Replace plastic cover over the sensor.

12. Plug harness into new sensor.

13. Replace crank pulley. I used a big bearing that came with a harmonic balancer installation kit (loaner from Autozone) to press the pulley onto the shaft. Sandwich the bearing between the pulley and the head of the crank bolt and tighten the crank bolt down pushing the pulley onto the shaft. When the pulley stops moving, remove the crank bolt and bearing. (Using the bearing just keeps the head of the crank bolt from turning the crank pulley while it's being pressed on. It made life easier, but probably isn't necessary. A bit of grease between the bolt and pulley would likely work as well.)

14. Install crank pulley bolt. I didn't have an impact wrench or an easy way to keep the engine from turning so I tightened the bolt as best I could and then gave the ratchet a couple of hits with a deadblow hammer to shock load it a bit tighter.

15. At this point I reinstalled serpentine belt, reconnected the battery, and fired it up just to make sure everything worked (glad I did b/c I had a problem and needed to get back to the sensor again)

16. If everything checks out, reinstall the wheel well cover, wheel, and let the car down.

17. (Quasi-optional) Take the car to a GM dealer or equivalent with a Tech II to have a "Crank Variation Relearn Procedure" done.


If anyone wants to add pics, detail, or correct something please feel free. It would be nice to get a good writeup on this procedure posted again.

Good luck!

Ryan


Note: This was based on my experience with a 1998 Grand Prix GT 3.8L