Electrical Module Locations?

[Avenir-2020]

Hello everyone.
My wife's 2018 Regal Sportback Essence 2.0L is having some electrical issues. Very intermittent, but getting worse.
All sorts of warnings randomly pop up on the instrument panel:
Stabilitrak, Advanced Lighting, Power Steering, Speedometer bouncing, etc. Intermittent Codes are P0700, U0073, U0101, which are communication issues with Control modules.
The new trick is it randomly won't start, but eventually does. Battery is 3 months old and is Not the issue.
I've narrowed it down to either the Body Control Module or Gateway Control Module (leaning towards this one based on symptoms). Where are these modules located and do they both need to be dealer programmed?
Thanks in advance for any help...

 

[Jack GS]

How long has this been an issue?

Reason I ask is if this all started about 3 months ago, I'd say you got a bad battery or possibly a bad connection (loose nut) at the battery. I know you explicitly ruled out the battery as the issue, but just clarifying. These vehicles are very sensitive to battery levels.

Edit:
AWD or FWD?

This dictates which transmission is equipped and may make a difference with diagnosis and locations of the modules (doubtful but being thorough)

 

[Avenir-2020]

How long has this been an issue?

Reason I ask is if this all started about 3 months ago, I'd say you got a bad battery or possibly a bad connection (loose nut) at the battery. I know you explicitly ruled out the battery as the issue, but just clarifying. These vehicles are very sensitive to battery levels.

The electrical issues began prior to replacing the battery (that's why I replaced it) and are very intermittent. Like once every few weeks. The battery is Not the issue. It is a communication (module) issue.
FWD 2.0L

 

[Jack GS]

I can provide the module locations tomorrow if someone else hasn't already.

As I'm sure you have, I found multiple instances on other GM product forums pertaining to the same issue. Most never report a solution, but one did and the issue was the TCM.

 

[Avenir-2020]

I can provide the module locations tomorrow if someone else hasn't already.

As I'm sure you have, I found multiple instances on other GM product forums pertaining to the same issue. Most never report a solution, but one did and the issue was the TCM.

L

Post in thread 'Electrical Issues?'

Oct 30, 2023

Final update for everyone.

I get the phone call from the dealer saying that the car is ready to be picked up and everything is working normally again. It ended up not being the BCM but rather just the gateway control module. They found this by replacing the GCM and they were still having problems with it talking to the BCM. They got on the phone with the GM Service Tech line and they recommended putting the original BCM back in as the new one was most likely a bad part from GM.

They put the the old BCM back in the car and everything ran normally. They did a test drive to make sure...

• Lugen

 

[Jack GS]

The Serial Data Gateway Module is located under the dash on the drivers side. It is directly behind the OBDII port and is oriented with the two connectors facing downward. It is retained by a plastic tab.


The BCM is located in the passenger side inboard footwell, behind the carpet. It is also retained by plastic tabs as shown.

 

[Avenir-2020]

Fantastic! Thank you Sir.

 

[Rose011]

Hello everyone.
My wife's 2018 Regal Sportback Essence 2.0L is having some electrical issues. Very intermittent, but getting worse.
All sorts of warnings randomly pop up on the instrument panel:
Stabilitrak, Advanced Lighting, Power Steering, Speedometer bouncing, etc. Intermittent Codes are P0700, U0073, U0101, which are communication issues with Control modules.
The new trick is it randomly won't start, but eventually does. Battery is 3 months old and is Not the issue.
I've narrowed it down to either the Body Control Module or Gateway Control Module (leaning towards this one based on symptoms). Where are these modules located and do they both need to be dealer programmed?
Thanks in advance for any help...

The Body Control Module (BCM) is usually located behind the dash, near the fuse box or driver's side. The Gateway Control Module is typically near the center of the vehicle, under the dash or behind the console. Both may need dealer programming, especially if they are replaced. Since you're getting communication errors, the Gateway sounds like a likely culprit. I'd suggest checking connections first, but if it keeps acting up, a visit to the dealer might be needed to get everything properly reprogrammed.

 

[2018 TourX in Texas]

The Serial Data Gateway Module is located under the dash on the drivers side. It is directly behind the OBDII port and is oriented with the two connectors facing downward. It is retained by a plastic tab.
View attachment 48259

The BCM is located in the passenger side inboard footwell, behind the carpet. It is also retained by plastic tabs as shown.
View attachment 48260

Thanks for posting this !
Are these locations the same on the 2018 TourX Wagon ?

Also - can you point me to the fuse / relay box location ?
Is there more than one ?
I'm getting a crank / no start condition.

The code showed for a "fuel pump driver control module" - which I'm trying to locate. -- if anyone knows please clue me in & Thank YOU !

DAVID

 

[Jack GS]

I would recommend to anyone searching for modules or specific fuse block locations to look at the service manual. I have provided the download link in the forum if you search "Service Manual"

Once you have the manual downloaded, using the crtl+f function allows you to search the entire document.

 

[2018 TourX in Texas]

I would recommend to anyone searching for modules or specific fuse block locations to look at the service manual. I have provided the download link in the forum if you search "Service Manual"

Once you have the manual downloaded, using the crtl+f function allows you to search the entire document.

Ok Jack I have downloaded & opened it in my Laptop.
So we use the CRTL key + F to locate / search for any particular terms ?

I was wondering about that I didn't see an Index listed anywhere.

Much thanks - David in Texas

 

[Jack GS]

Ok Jack I have downloaded & opened it in my Laptop.
So we use the CRTL key + F to locate / search for any particular terms ?

I was wondering about that I didn't see an Index listed anywhere.

Much thanks - David in Texas

Yes, there's not really any good way to quickly jump to a particular section. Searching keywords is the best way to do it, but be careful about the words you choose... it's a large document to search.

 

[2018 TourX in Texas]

Ok that makes sense.
Another way to access drawings on a particular part I used today:
Go to Buick / GM dealer parts counter, I had a part description & "perhaps" part # - also have the last 6 of your VIN.

The parts manager was able to pinpoint the updated part #, quote a price, print me the drawing of where to find it - all of which will help me greatly.

(This was for my "Crank / No Start" Issue that's showing a code pointing at a bad / intermittent connection "fuel pump power control module" - a rare problem, judging by my lack of responses to my thread.)

 

[DrFaustus]

The service manual was really clutch for my dash cam install. I was able to plan the route of the rear camera wiring before doing anything. Knowing exactly where all the various clips were to get into the headliner with the cable and back into the rear hatch. I'm sure it saved me a lot of frustration and foraging around for fitment.