what causes loss of communication with transmission?

Asked by Jul 29, 2013 at 06:47 PM about the 2007 Chevrolet Cobalt

Question type: Maintenance & Repair

speedometer stoped working and it will not change gear. check engine light is on and it also indicates a problem with the power steering. I had a diagnostics test ran at auto zone and that's what it read loss of communication to transmission. what can cause this and how do I fix it?

7 Answers

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~

6 of 6 people found this helpful.

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~

2 of 2 people found this helpful.

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~

2 of 2 people found this helpful.
140

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

2 of 2 people found this helpful.

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

15

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?

1 of 1 people found this helpful.

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..

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