Nickocosmic

http://www.youtube.com/watch?v=tSbfdlGZwHM

just posted this video showing what's happening with my car. it's a 2006 cobalt ls automatic. this happened once about a month ago on i-75. thought the car was overheating, even though there was no indicator light for it. saw that my coolant was low, added some more, and the problem went away. until yesterday. has been doing this since. i just had the power steering motor replaced by the dealership thanks to the recall. i don't know if this is an electrical issue, but it seems like one. any help is greatly appreciated. thanks is advance.

Malaclypse

iTrader: (1)

No way to be sure without a scan tool and some codes. I could sit here and guess all day and never come close.

Nickocosmic

yeah, i'm going to the auto parts store tomorrow and gonna have them have a look. just one question though. does the scanner post a code if the check engine light isn't on?

Nickocosmic

okay, got the codes. oddly, the first time they scanned it, it didn't show any codes. the second time, three sprung up:

p0700 transmission control system

u0101 lost comm. w/ tcm

p0128 coolant temp. below thermostat

the guy said these were all sensors. anyone ever have to have these fixed? if so, what was the cost?

Nickocosmic

well i found out that my tcm is fubar. called up a salvage yard to find one, but they don't have any 2006 cobalts. are the tcm's the same for all years? and if i get a used one, does it have to be reprogrammed?

scottie

That is no good man. Usually you have to have ecms/tcms flashed per vehicle. But I can't say 100 percent.

army_greywolf

iTrader: (2)

Stop before you go any further. Did this develop immediately following the power steering motor replacement?

If so, I know exactly what happened. They damaged your harness during replacement, this happens when the oil change guy gets taught how to do the recall.

Nickocosmic

no, it actually first started about 2 months ago, on I-75 no less. but I told the dealership that it started after they replaced the power steering motor lol.

army_greywolf

iTrader: (2)

Since I work for a logging equipment manufacturer that should put me off but it's GM aka the guv'ment.

Sooo no transmission shifting? What I am seeing, looks like a ground problem.

Nickocosmic

well, it wouldn't shift out of first gear, and if kept at around 3-4k rpm long enough, it would finally shift, albeit very jolty. the speedometer would begin to work as well, but i would still get the power steering error.

edit: if it were a grounding problem, how would i go about finding/fixing it without money or equipment?

army_greywolf

iTrader: (2)

First thing is first check your battery, the root of all evil so to speak. Next you need to check the ground for your engine, I am not sure if there is another for your transmission. Basically you want to go through and verify by hand all connectors to the transmission, then to your computer. I know for a fact there is a trans relay on base model cobalts, it's in the fuse box under the hood it might be labeled bcm/tcm or "overdrive" or just trans. One of our service techs bought a used cobalt for $800 bucks brought it to the shop on a flatbed with what we were told would be a trans job. It was a relay. I would be sure your electrical components are tight nothing is broken and you haven't run over road kill or pieces of tire recently have you?

Nickocosmic

I havent hit anything with my car, and had the dealership put in a new battery, as the guy suggested it was a voltage problem (and the old battery was leaking) but am i just checking the fuse box? Of do i need to jack/ lift the car to check the grounds? I'm not very mechanically inclined, mind you.

army_greywolf

iTrader: (2)

I'm leaning on bad battery connections. Even a bad alternator, I look for root cause, a TCM is just a sub component of your ECM as far as I can tell there are only two actual computers on Cobalts one of them is your ECM that controls powertrain functions and then there is the BCM which controls body and chassis functions. High Frequency interferrance is a common do not pass go on modern computer controlled engines, it screws up the readability of sensors among other things. And that comes from your alternator. In the old days a tell tale was a hf interference in your radio right through the speakers that was in time with engine speed, most of the time that meant bad plug wires or a cap and rotor, these days that means the rectifier has **** the bed on your delco alternator. It will still charge and do what it's supposed to do it's just a burnt out suppression circuit inside it. Anyways, there is an easy way to tell. Disconnect it. which means you have to crawl under the car, put really, cant miss it, disconnect the thick + lead to it, tape both ends over start the car, if magically it behaves, you found your root cause. This is not to say it wouldn't act up in the future, most things in electronics are irreversable without professional "rehabilitation".

A BCM is programmed to the car, done at the dealer, yes you can get a used one, but it won't do alot of good since they are hard to find in the U PULL IT yards. ECMs can be swapped so long as it's from the exact same engine/transmission configuration.

From what I saw in the video, your ECM is not receiving a transmission speed output signal, the outside temperature works intermittently and the power steering is intermittent as well. This all tells me you have a voltage problem.

On a final thought, you can try putting your battery on a charger capable of 30 amps or so for about an hour and then immediately take your car for a drive afterwards. This will top the battery to around 13.6 volts which is well within range the car sees as normal. If it suddenly decides to behave under this condition, time to replace your alternator if you've ruled out the battery.

Oh and remember, new batteries have a proven 5% factory defect rate. A condition where they go bad in just a couple months, yet still pass the QA/QC at the factory. Can't be helped, just remember it happens.

Before I log off for the night, I'll ask a few more questions.


Does the car change behavior w/ac on? when you turn the auto headlights off does it drive better? Does temperature or weather affect performance? Was it exhibiting the power steering failure before this combined problem, since I am trying to rule it out as related.

Nickocosmic

army_greywolf, let me just say that so far you've been more help than anyone, and i really appreciate it.

i tried to use the jack that came with my car to get it up, but i don't trust the jack, so i gave up. but while i was under there, i couldn't tell where the positive connection was to the alternator. i was under the front passenger side looking at the alternator. however, i had to start the car and get it off the driveway as it was on an incline, and everything worked fine except i was still getting the 'check engine' light.

as far as charging the battery with a charger, i'll have to see if my friend has one i could borrow.

the car doesn't change behavior if the a/c is on or off. i've also turned off the radio with no results. i haven't tried it with auto lights on/off. i don't know if temperature affects it, as i live in florida and it's hotter than hell all year. however, the first time it happened (almost 2 months ago), i thought the car overheated. when i checked the coolant level, it was really low. so i topped it off, and it didn't act up again until last week. coolant level is at full. weather doesn't seem to affect it as far as i can tell. it also seems like the power steering problem is tied to everything else, as if something is causing a system-wide failure (which is why i suspected electrical).

edit: actually, i remember hitting an armadillo about a week or so ago (he was fine, got up and ran off). it was too late to try to dodge it, so i aimed right down the middle of the car to try to avoid hitting him with my wheels.

Nickocosmic

okay, so according to army_greyworlf, it's looking like a voltage issue, which in this case means alternator. is it recommended i get a new one or can i get a used one online?