Thread: Tac quits and goes to zero/trac off light comes on

I have a problem and need imput. While driving my 99 grand prix gt,sometimes intermitantly, the engine will miss quickly, then the tachometer will go to zero and quit working,while at the same time the trac off light comes on. The engine continues to run normally, just with no rpm reading. i can stop ,turn off the ignition key and start the engine back up and the tach will work as normal and the trac off light goes off. There are no ckeck engine light codes that are associated with this problem.
any one else have this problem. if so what fixed the problem....

I'm having exactly the same problem with my '99 GT. It started last summer and happened pretty randomly until winter. For whatever reason it didn't happen at all this winter. Just today it finally did it again.

In addition to this, I'm having another problem that I think is related. I'll go to start the engine, and it will crank and crank, but not fire. After multiple attempts and a few minutes later, it will just all of a sudden pop right off when you hit the key and idle perfectly like nothing was wrong. If you just let it sit for several minutes, the same it will start too. The reason I feel these problems are related are that they started happening at the same time, and they appear to both be electrical issues affecting ignition.

I have had the car into a couple mechanics, but like you said - there are no codes in the system and everything checks out. I think it would have to act up with the diagnostic equipment hooked up to see anything.

So, unfortunately, I don't have a solution, but I'm as interested as you are in what it could be.

One thing that was suggested to me that I haven't tried yet is to swap out relays in the fuse panel under the hood. Is there any possibility that a relay could be causing these problems in the ignition circuit?

Eric.

2 me it sounds like the crankshaft position sensor going bad. For more info on replacing it take a look here.


Crankshaft Position Sensor Replacement '97-'03 - Automotive Forums .com Car Chat


hope this helps solve the problem:

Yes Mine also has the cranking issue ,exactly as You described it also.

Alot of the reasearch that I have read also says the crankshaft position sensor....

my 1997 gt does that too except for the trac off light doenst come on. the tac just dies

It is the CPS !!!!!!!!!!!

Thanks, i will be changing the crank position sensor this weekend....hal

man my car did this and is still doing this...
I think Im going to have someone replace taht sensor for me this weekend...

okay.....I am a woman...lol and I have owned my 99gt for 7 years since it has had 30,000 miles and it now has 170 miles. I have had this very problem with my car on and off for 3 years....being a woman of course doing nothing. I am at the point now where I have let the problem go on so long that it has not started due to me killing the batterie and then having to leave the car and come back to It like a few hours later then getting it jumped and starting right up..........only to stall like a mile away. thus me leaving it there and getting it towed to the shop the next day......the stalling was so bad that I had to replace the starter from having to crank it so much so that it would start while being stalled on a busy street or late at night on the freeway.........FRANTIC for it to start...chick.....car problems..lol Now I am having the problem of it being at the mechanic for two weeks and them not knowing what is wrong with it cause it is starting up and driving around for them just fine.....prob not going on trips and stop and go traffic......so they really arent listening to me when i say it is some kind of sensor.....it runs awesome and then just stalls along with all these signs that always happen right before the stall of the tachometer going to 0 and the trac off light coming on and the enginge studders then dies...... I also was trying different things to see whats up and had it in 3rd gear and it did the usual before it stalled but instead of stalling i would push on the gas and it would just rev...then i slipped it into drive and then it stalled.....please help me cause these mechanics are saying other things.........

Replaced the camshaft position sensor and it still sends my tac down to zero about half way in my ride to work. Will have to replace the Crankshaft position sensor to see. It also could be a short somewhere too.

Did you read through this post (from 2009 btw) at all?? You should have started w/ the crank position sensor. This is the usual suspect when dealing w/ the issue you stated. Hold onto your old cam position sensor as it probabaly works fine.

Check the wire harness to the crank position sensor and see if its chaffed anywhere. If not, then replace and enjoy!

Welcome to the site!

I have a '97 SE with the 3.8 NA. Owned for about 5K miles now 164K. I've got problems with electrical systems. I get low trac light for like 3 minutes, then check tire pressure and trac off lights both come on and stay on until restart. Pretty sure its a hub sensor though, no tach problems.

Related to your post: my car is always easy to start, but warm starts exhibit the strange symptom of suddenly and very abruptly snapping right to a certain idle speed, followed by chugging for 5-10 seconds. After that its all good. Note: I just realized my "micro relay" #15 in the engine fuse box is gone, it is for fuel pump/speed control or something of the like. Not meant to be missing according to the diagram! Also, my post mentions a slow mist of oil residue coming out the back of the engine which is in itself a problem, in addition to soaking various wires and parts of the electrical harness.

Currently I'm working my way into the engine from the airbox cleaning and replacing anything thats compromised before paying a mechanic. Right now I'm at the throttle body, and next the actual fuel lines and fuel injectors. Its kind of a process of elimination but heres my thread if you want to follow along with it.

http://www.grandprixforums.net/chug-...ned-44927.html

1997 Grand Prix 3.8 L GT 120K miles

About a month ago I replaced my water pump (2nd one in 100K miles). It sprayed anti - freeze all over the place. So I cleaned the engine and replaced the camshaft sensor. I guess I will try the relay fuse first then replace the crankshaft sensor. I dont know if the anti freeze got to some of the sensors or destroyed some of the parts, so I will eliminate one thing one by one.

I replaced the crankshaft position sensor and the tac doesn't have any problems anymore. The car runs great, with no hesitation.

My 99 GTP has been doing this for a few years and I think I am convinced it is the CPS after reading from this thread. But one question I have from the original post from 'holorinhal'. He states, "The engine continues to run normally, just with no rpm reading". Does this mean that the engine shuts off, then comes back on and continues to run normally or it never shuts off and the tach just happens to go to zero? Here is why I ask - as I am driving down the highway, the tach will go to zero for maybe 1 second, but my engine dies during this 1 second. Since the car is moving, it restarts itself and its then like nothing ever happened. The tach has gone to zero when sitting at a stop light too (rarely), and when this happens, I need to manually restart the car. Always restarts with no problem. These momentary "shutdowns" have been occurring on average about once every couple months for a few years. Do my symptoms still sound like a bad CPS or something else? Thanks!

Yep, still sounds like a bad CPS to me.

Thanks for all your posts everyone. I just had the tach/trac light problem for the first time and within 2 minutes, you have diagnosed the problem AND given me a great step by step(with awesome photos) how to....http://www.grandprixforums.net/cps.php. I think I'll send some love($$$) this way whan I'm done fixing this---LOVE THIS SITE!!!!

I just completed this R&R yesterday and the instructions found here were AWESOME!!! They probably saved me several hours of running around with dirty elbows finding all the parts I needed to do this job( Lowe's has the 1/4"-X" bolts needed for the H.B. puller...) A big "Thank You" goes out to everyone here who takes the time to posts hint/tips posted on this forum

I'm having the same problems here. Tac goes to 0 whenever it wants and then when i start the engine it begins to work again. went to auto zone and the diagnostic test said i had a bad crankshaft position sensor, bad knock sensor, and a bad O2 sensor. I figured I'd wait to buy the position sensor because i wanted another opinion on it but after reading this i'm going to get it. The guy at the store gave me instructions on how to replace it and it seems pretty simple, as for the knock sensor i really don't care because im 99% positive the engine does not have a knock and just a faulty sensor. My O2 sensor is the last fault that i had and i think it is due to a bad gasket near my catalytic converter, it makes a noise as if there is a flutter in my exhaust, if you would post another reasons for these problems please let me know! Thanks