We have just bought a used Blazer. After 3 weeks the thing would not change gear. The mph dial wavers up and down, too. If you let it sit a while, then drive it it may jump into second gear, then that is it. Reverse works ok. I did play around underneath and for a time it worked fine (a short time!). NOw it is back the way it was. Would it be the PCM? Or the speed sensor? I have limited dknowledge but just read the manual.. is was real vague...... Tranny oil looks and smells fine but level is way over the full mark (related?)

Is the check engine light on? Does it start out in first gear and stay in first gear? If the check engine light is on it sounds like electrical problems with the wiring or control of the shift solenoids, or possibly a vehicle speed sensor problem (the fluctuating speedometer). If it is an electrical problem and turns on check engine light it should go into default and start out in third gear and reverse won't be affected.

I looked at it again today (Sunday 23rd NOv 03). The speedometer still goes from nothing to regular speed then nothing, all the time. Sometimes not even doing that, just sitting still. I can manual select first gear and second and it works ok. When I used 3rd or Drive, it feels like it slips in gear or does not know what gear to select. Is it expensive to get a computer put on it to check? I am not sure where one is near though (Zip 36502). I could change out sensors etc and waste money. I hate this ! Could it be the PCM computer... I do not mind spending some money if it gets fixed.... for sure !

The engine light does come on sometimes, we have even had the Anti Lock Break symbol come on too, yet the anti lock does still work.

Her borther has a Blazer, is it worth swapping out the PCM to see if that cures it or would that mess his up, too ???

I would not recommend trying a PCM out of another vehicle. I would recommend finding a transmission shop at this point and see if someone will look at the transmission fluid (color and smell) and drive it so they will know for sure if it is slipping. The transmission shops around here will usually take it for a quick drive and let you know if it needs attention. Good luck.

i had a short in my engine harness which killed everything. i fixed that, then had basicly the same problems you described with the trans. i talked to friend at work he went out and started to check fuses. he found the 'ecm' fuse blown. boy do i feel stupid. i mean, here i was thinking it was my pcm itself that was bad. my susgestion is to check ALL the fuses. a $0.50 fuse is better than $50.00 or more garage fee.

hmmmmmmm........ is that fuse located under the hood or inside the car. I checked the ones under the hood and they seemed ok...

Would that not cause the motor to stop too.. Good point thoughhh !!

i have a 93 blazer, so i couldn't tell you( different style). all i'm saying is sometimes we forget the basic things when we look at our problems. pull every fuse you see. should only take 5-10 min. is there a fuse panel under the dash? as far as motor stopage is concerned, no. unless the circuit involves a component needed to run the eng. i.e.: fuel pump(to get fuel to the eng), altenator(to keep the battery charged), ect..

Go to Autozone and have them check your check engine codes for free. (Not all codes will trip the light, by the way.)

Also, you may want to consider an extended warranty. Buying my Jimmy used at 56k miles, I added a 50k mile/4 year warranty for $2000. Experience tells me it will pay for itself. $100 deductible per incident. Below is a link to the provider my dealer suggests for GM vehicles.

http://www.efgcompanies.com/Products/Mapcontracts/mapcontracts.html

Good luck!