Hey guys,

Brand new here and I got a question. I recently bought an 04 Monte Carlo SS for my wife. I got it real cheap with some issues. The biggest of which is the transmission not shifting out of first gear. The radio displays LOC and pretty much every light in the car is on. ABS, service traction system, sometimes the brake light is on, the speedo doesn't work and the fuel gauge bounces all over the place. However, I can disconnect the battery for 1 hour and the radio works and it will shift just fine, until the car is turned off. Then back to square one. I've already replaced the PCM thinking it may have been faulty but there is no change in the car. I also know that I need to replace the hub to fix the abs and traction lights. But with the radio saying LOC and the car not shifting out of first gear, I'm thinking something with the security system. Thoughts?

Thanks in advance!

 

Hello and Welcome to the forum!!

I had very similiar issues, ended up being the BCM (body control module) was abou $500 or so, the dealership has to program the new one. Guess you could read up on signs of BCM failure on the net and see if you think they are similiar to yours.

 

It's a bad BCM partially. They're $120 on amazon new.
It takes 15 minutes to put in yourself. It'll take 30 minutes to relearn security (3 cycles, turn key to crank and leave in on position for 10 minutes until security light turns off, turn to off and then repeat 2 more times) and then the car will start and you can drive to a dealer for them to finish the programming.

The idiot lights and LOC on the radio (and likely keyless entry doesn't work) is the BCM.
The not shifting out of first gear could be related as well but it's not a typical symptom.

I'd personally throw a BCM in it, do the key relearn and see how it drives (if it shifts out of 1st) and if the ABS/TRAC lights go away. If the ABS/TRAC remains I'd take it to a place like advance auto for them to read the codes for free.

 

Hey guys,

Just an update, new PCM wouldn't let it shift at all. Put the old PCM back in and replaced the speed sensor on the transmission. It does much better, but still not right,and the radio LOC and idiot lights are still on. The speedo tried to work but would act kinda wacky so I'm pretty sure you guys are right with it being the BCM. Still got a long ways to go on the restoration of this car, but it's my wife's dream car, so it'll be worth it.

Thanks a TON!

Wayne

 

I just bought a 2001 ss and having the same issue with the fuel gauge going haywire! Actually ran out of gas for the first time im my life! I know my MAF sensor needs to be replaced and Im going jjnk yard shopping later do you guys think the BCM is bad too? Bought the car for 900 dollars so I dont mind sinking money in but mechcanics keep failing to tell me all the problems in one shot...

 

Going haywire how? When the gauge read low did the low fuel light also come on? It could be a bad stepper motor or bad sending unit. If you have and ODBII reader that can read fuel level it might be useful to compare it to the gauge behavior. If the ODBII reader goes haywire too I say BCM or sending unit. If the ODBII data is correct but the gauge is haywire I say stepper motor.

 

I am having the same issues as well in my 03 Monte LS. I have a New BCM and taking it to shop Wednesday to have it programed. My question is how long after I do the key re-learn do I have to get it to shop?

 

Once you do the 3 10 minute key relearn cycles the vehicle will start and drive just fine with no defined timeline of you need to get the BCM programmed by __ date or it will stop running. It's just that the options on the vehicle and things like the radio won't work until the BCM is fully programmed with the sticker info in the trunk.

 

I bought a used BCM on ebay trying to save a buck and took it to the dealer for reprogramming and they couldn't reprogram it due to it being secured by the last vehicle... just bought a new BCM to be reprogrammed....132 bux on ebay. And the kicker is everything works... lights, locks, key fobs, radio,etc.

 

Well I guess that's a plus. Thanks for the update and glad you got everything working.