what causes loss of communication with transmission?

hate to sound like a stuck parrot here on cargurus....but the black cable that connects to the chassis must be wirebrushed with a coarse wirebrush so that solid ground can be achieved...this connection must handle 300 cold cranking amps and also the delicate 750 mA of the ECU...so it is imperative this one be free of corrosion or anything what may cause "brown power" to happen creating an ECU failure~

get a NEW battery if five years old or older~ could mean trouble for your alternator and charging system as batteries will stop accepting a charge 10%/yr. get a good one NAPA, prestolite, Interstate....make us proud~

on a side note this connection when pulling the 300-700 cold cranking amps will "weld" the connection...just like an arc welder works...and will leave you with a corroded with electrical action (corrosion) to create this condition in the first place...normally it is alright as the ECU can see thru the corrosion to the good power, but varying amperages and voltages is the stuff ECU failures are made of~

i had the same problem disconnect the battery in the trunk for 30 minutes take out two fuses #25 10 amp and the 2amp above it replace them both then clean the fuse holder the computer is next to the fuse box check every wire in the connector by touching and moving it this is the fuse panel in the passenger side of the console when you are finished it will be fine

im haveing the same problem with no engine light on it says power steering and air bag service watch a couple movies to see if it will help did't back to sqaure one any anwsers

my colbolts check engine light came back on right after it got fixed then today the speedometer stopped working and it was working perfectly yesterday anyone know what they could be?

07 cobalt had same problem with my speedometer not working and wouldn't shift in OD. I found a video how to fix the problem.. and it worked.. just to make a good ground wire from the TCM and connect to the nut on the strut to ground it..

hello. don't have answer to anyones problems on how to fix their cobalt problems....My problem is the same as everyone else, but mine is a manual transmission...Any ideas?

Had the same problem on my 2005 chevy cobalt 2.2 automatic. There is a speedo sensor that connects near the transmission in the back of the engine bay super cheap and easy to change. Spliced it in a sottered it baout 6 months ago havent had any of the problems since. Hope this helps.

Just make sure u splice it far enough that the wires are well in tact.

Had an issue with my 2006 cobalt ss with the traction control power steering and not shifting from first gear and speedometer not working i changed the vss sensor on the transmission and all better.

Just run ground wire from ur tcm to strut gound just had same prob on 05 cobalt fixed it

That run a wire from tcm to strut tower is a lie total bullshit i have traction off sevice airbag service power steering service abs it will not give me top gear in theautomatic trany and speedometer not working replaced speed sensor ran that wire and no change zero fix