The ECM and battery was disconnected on my 2008 Equinox for head gasket replacement. After 4 days, the car will not turn over. My code reader does not connect to computer when plugged in to car. No security light on dashboard. I tried the key reprogram anyway. I even tried another ECM, same results.

 

When you say "the car will not turn over", do you mean the starter is not engaging at all (you hear nothing when you turn the key to the start position) or do you mean the starter is engaging but the engine won't start running on its own?

 

Just so we are all on the same page.in this thread, Won't turn over (starter does not engage) Won't start (starter turns but engine won't run). Starter will not engage. Battery is new and fully charged. Acts like the key security feature but I have already did a reprogram even though the security light is not showing on the instrument panel. Can't believe computers need to be reprogrammed if removed from the car..I am checking to see if I can take just the ECM to get it reprogrammed. I don't see why you couldn't, you can buy them off the net programed with your VIN and mileage. I think it's the ECM because when my code reader is in, there is no communication between the two. Any input would be appreciated.

 

If it were security issue, nothing but idiot lights would come on.Can you manually "bar" the engine over to make sure it is free to turn?

 

I don't think it's the ecm, as you stated tried a different one with same results. Yes, I have replaced the EM in my lumina, sent the vin to a guy on ebay, and viola. Are you getting a communication link error with your scan tool? Have you tried a different scan tool?

 

Problem resolved. Moving the wire harness around under the hood. I found a connector not all the way pushed in. Thanks for all your input and help. Drives great, no codes, no lights for the first time in a year. Thanks.

 

The ECM and/or BCM don't need to be reprogrammed if disconnected from the battery for a prolonged period of time. You probably have a blown fuse somewhere. The fact that the scantool can't communicate with the vehicle is a telltale sign that the fuse for the Data Link Connector is most likely blown. Check the 10A HVAC/RFA fuse in the interior fuse block along with any ECM/BCM related fuses in both the underhood and interior fuse blocks.

EDIT: I just saw that you got this resolved. I'm glad to hear it was something simple.

 

I appreciate all the help. Thanks

 

I’m having similar problem with my 2008 equinox sport
engine won’t crank
new battery
new starter
first problem was intermittent
engine wouldn’t crank after going to store
checked cables, gave it a boost , still the same
after a while I just kept repeateded turning on ignition and boom it started. Over the period of the next week it started fine, maybe pnce or twice I had to do the key on and off thing but it started. Then one morning it failed to start no matter what I did
.
im a licensed mechanic and I put it in shop thinking it was starter solonoid

after replacing starter it was still the same
i then put a jumper wire from solinoid to battery
engine finally cranks over but no start.i put my code reader and it fails to connect, same as previous posts in this thread. I’ve spent 8 hours checking connection etc and no luck
HELP

 

Check and make sure your relays are good and have a good connection - particularly relays 31 IGN1, 47 PWR/TRN, and 55 CRANK. All of these relays are in the underhood fuse block. If any of them is anything but super tight when trying to remove them, I'd suspect a bad connection. You can try wiggling each relay while a buddy turns the key and tries to start the engine.

Sometimes the terminals in the fuse block that pinch the relay terminals work themselves loose. The solution is to remove the fuse block, take it apart, and gently squeeze the terminals back together. This sounds harder than it really is. Take good pictures of the fuses & relays beforehand so you know exactly how to put them back.