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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), GMC Mechanic
Category: GM
Satisfied Customers: 5789
Experience:  GM Grand Master Technician 2007. 14 years experience.
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Replaced the motor in a 2010 Acadia. Now the square

Customer Question

Replaced the motor in a 2010 Acadia. Now the square indicator on the dash showing what gear the Acadia is in is not there which is making the car not start as if it's not in park. Tried putting it in neutral no luck. Tried unhooking the battery no luck. Any ideas?
JA: How old is the transmission? Have you checked the brake switch?
Customer: 2010 only 60k. Brakes are illuminating
JA: Are you fixing your Acadia yourself? What have you tried so far?
Customer: Yes we are a used car dealer with a service shop. We are getting a code U0100
JA: Anything else you want the mechanic to know before I connect you?
Customer: NO
Submitted: 2 months ago.
Category: GM
Expert:  david craig replied 2 months ago.

Hi Im David, thanks for visiting the site. Double check the connections to the transmission. This fault code can be caused by a plethora of things and needs to be broken down to sub codes.

Customer: replied 2 months ago.
David we have triple checked all the plugs and made sure they were connected
Expert:  david craig replied 2 months ago.

well you're missing something. put a scan tool on it that breaks the code down further to communicate with the control modules.

Expert:  david craig replied 2 months ago.

adjust the transmission range switch and check it for the proper voltages and grounds

Customer: replied 2 months ago.
Neutral Safety Switch?
Customer: replied 2 months ago.
Do you have time to talk on the phone?
Expert:  david craig replied 2 months ago.

yes, neutral safety switch. ill send you the adjustment

Customer: replied 2 months ago.
We left a battery saver on the entire time during the engine swap. Could this have been the cause of this? Disconnecting the grounds and such and confused the computers?
Expert:  david craig replied 2 months ago.

always a great possibility

Expert:  david craig replied 2 months ago.

do a master reset. disconnect both battery cables. rub the terminals together for 30 seconds, let them hang loose gor 30 minutes then reconnect.

Customer: replied 2 months ago.
Ok. We left the battery unhooked all nightso we need to rub them together and then sit for 30 mins?
Expert:  david craig replied 2 months ago.

yes and here is the adjustment

Customer: replied 2 months ago.
While the battery was disconnected last night we had the cables touching each other for the night. Would this have done a master reset?
Expert:  david craig replied 2 months ago.

I never tried leaving them together that long. try the 30 second, 30 minute procedure

Customer: replied 2 months ago.
Ok we will give a shot. If it doesn't work will this conversation still be open?
Expert:  david craig replied 2 months ago.

open as long as it takes my friend

Expert:  david craig replied 2 months ago.

I have to get to my shop. Ill be back on in an hour.

Customer: replied 2 months ago.
Ok thank you
Customer: replied 2 months ago.
Ok I thought we had it my friend but unfortunately not. The indicator light came on it stayed on and the motor cranked. I went to try again after the new motor didn't fire right away as its first start and the light went away and back to the same issue? Any ideas?
Customer: replied 2 months ago.
The info window is saying traction control off, service traction control and service stability trac.
Expert:  david craig replied 2 months ago.

ABS light on also?

Customer: replied 2 months ago.
Let me check
Customer: replied 2 months ago.
No ABS light. Just the traction control light and battery light. It now says service battery charging system but it could just be low
Expert:  david craig replied 2 months ago.

ok, its very important to keep the battery charged to at least 12.5 vdc while checking things.

Customer: replied 2 months ago.
I'm just wondering is it stuck in some kind of safety mode? The transmission is about 2 quarts low but we wanted it to run and then add the fluid would that effect it? When the first motor stopped because someone changed the oil and never put new in the car was driven 5 miles or so and it shut down which obviously blew the motor. The car did the same thing it would not turn over at all like the battery was dead. No noise when the motor blew no warning lights just shut down. Do you think it is stuck in a safety mode? If so how can that be erased or fixed?
Expert:  david craig replied 2 months ago.

The only way this can be determined is to find out why the U0100 code is present. This can only be accomplished with a GM TECH 2 scan tool. I cant tell you which modules the ecm is not communicating with over a data bus. There is a limit to what we can do on here. This is going to take the correct diagnostics that I have already attached.

Customer: replied 2 months ago.
We did the diagnostics that you suggested. What we have found is the ignition relay may be the issue? When the ignition is switched on the relay is making a buzz/vibration sound. When it is off nothing. We tried a different relay and it does the same. Any help or direction would be appreciated.