Check engine light on . . .
Thread Starter
Team Owner
Joined: Mar 2014
Posts: 21,631
Likes: 1,144
From: Below the bottom of Berby Hollow, NYS
Check engine light on . . .
Ha, well I knew it had to happen sooner or later -- I'm surprised it didn't happen sooner. Just last week I commented on some thread that my '07 with 34k miles has been trouble-free and that everything works.
Well it ain't no more. The engine light came on after I started it last night and was heading home. No weird symptoms and no DIC messages.
I plugged my cheap scanner in and got "U0073" and "U0073 P." I Googled them and got a bunch of stuff, wiring problems, loose connectors, etc. It's all jibberish to me.
What to do next? My go-to buddy is out of town for the week.
Well it ain't no more. The engine light came on after I started it last night and was heading home. No weird symptoms and no DIC messages.
I plugged my cheap scanner in and got "U0073" and "U0073 P." I Googled them and got a bunch of stuff, wiring problems, loose connectors, etc. It's all jibberish to me.
What to do next? My go-to buddy is out of town for the week.
Pro
Joined: Dec 2014
Posts: 708
Likes: 47
Ha, well I knew it had to happen sooner or later -- I'm surprised it didn't happen sooner. Just last week I commented on some thread that my '07 with 34k miles has been trouble-free and that everything works.
Well it ain't no more. The engine light came on after I started it last night and was heading home. No weird symptoms and no DIC messages.
I plugged my cheap scanner in and got "U0073" and "U0073 P." I Googled them and got a bunch of stuff, wiring problems, loose connectors, etc. It's all jibberish to me.
What to do next? My go-to buddy is out of town for the week.
Well it ain't no more. The engine light came on after I started it last night and was heading home. No weird symptoms and no DIC messages.
I plugged my cheap scanner in and got "U0073" and "U0073 P." I Googled them and got a bunch of stuff, wiring problems, loose connectors, etc. It's all jibberish to me.
What to do next? My go-to buddy is out of town for the week.
Mark
Team Owner
Joined: May 2000
Posts: 53,727
Likes: 5,613
From: Plantation Florida USAF(Retired) 1966-1990
U.S. Air Force
St. Jude Donor '05 thru '26
NCM Sinkhole Donor
My 05 last month threw on the check engine light after refueling. So I bought new gas cap, and the check engine light went out, for about month, and last week, it came back on again. So I just took a piece black tape over the check engine light. You know the old saying, out of sight out of mind.
Well today drive, the light went out again. I'll see how long with this time it stays off, have nothing on the DIC, and car has power.
So I'll just leave it alone, till the car needs to go to the shop for repairs.
Well today drive, the light went out again. I'll see how long with this time it stays off, have nothing on the DIC, and car has power.
So I'll just leave it alone, till the car needs to go to the shop for repairs.
Thread Starter
Team Owner
Joined: Mar 2014
Posts: 21,631
Likes: 1,144
From: Below the bottom of Berby Hollow, NYS
Although the battery is four years old, it is always on a tender when home. I load-tested it this spring and it was still excellent. So, who knows?
My 05 last month threw on the check engine light after refueling. So I bought new gas cap, and the check engine light went out, for about month, and last week, it came back on again. So I just took a piece black tape over the check engine light. You know the old saying, out of sight out of mind.
Well today drive, the light went out again. I'll see how long with this time it stays off, have nothing on the DIC, and car has power.
So I'll just leave it alone, till the car needs to go to the shop for repairs.
Well today drive, the light went out again. I'll see how long with this time it stays off, have nothing on the DIC, and car has power.
So I'll just leave it alone, till the car needs to go to the shop for repairs.
Last time I changed them was when I bought the new battery. Maybe they're due. 
Le Mans Master
Joined: Feb 2014
Posts: 5,463
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From: Chino CA
Race Director
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From: Washington Township Michigan
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Bruce, there is a GM Service Document with a lot of information on it related to U0073.
Majority deal with intermittent connections and power loss, as U codes typically refer to Can Bus communication. Attempted to save it as photos, would have inserted them here, but I stopped at 14.
Check underhood for any "chafed" wires on the intake manifold area first, easiest to see. Unless you are going to tackle this yourself, better off to wait for "your guy."
Majority deal with intermittent connections and power loss, as U codes typically refer to Can Bus communication. Attempted to save it as photos, would have inserted them here, but I stopped at 14.
Check underhood for any "chafed" wires on the intake manifold area first, easiest to see. Unless you are going to tackle this yourself, better off to wait for "your guy."
Thread Starter
Team Owner
Joined: Mar 2014
Posts: 21,631
Likes: 1,144
From: Below the bottom of Berby Hollow, NYS
Bruce, there is a GM Service Document with a lot of information on it related to U0073.
Majority deal with intermittent connections and power loss, as U codes typically refer to Can Bus communication. Attempted to save it as photos, would have inserted them here, but I stopped at 14.
Check underhood for any "chafed" wires on the intake manifold area first, easiest to see. Unless you are going to tackle this yourself, better off to wait for "your guy."
Majority deal with intermittent connections and power loss, as U codes typically refer to Can Bus communication. Attempted to save it as photos, would have inserted them here, but I stopped at 14.
Check underhood for any "chafed" wires on the intake manifold area first, easiest to see. Unless you are going to tackle this yourself, better off to wait for "your guy."
I will look tomorrow although I won't expect to see anything obvious. Everything is bone stock and the engine and surround looks pretty much like it did when new. But, that doesn't necessarily mean anything.
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Thread Starter
Team Owner
Joined: Mar 2014
Posts: 21,631
Likes: 1,144
From: Below the bottom of Berby Hollow, NYS
Yer a great buddy to have, always the one with the level head and somehow coaxing me off the window ledge.
Supposed to get a lot of rain tomorrow so the car stays in the barn. Maybe on Wednesday I'll stop at a local garage where I know the guys and have them check it.
Race Director
Joined: Dec 2002
Posts: 10,461
Likes: 1,149
From: Wayne Township WI
Given nature of code, wiring damage due to mice?
Can be hellacious locating damaged line(s) since it's a random location unlike known/documented chafe points.
Evidence of chewing @ harnesses etc are obvious tells, pray it isn't under dash.
But if inside a nest somewhere is in play, also.
Been down this road twice, living in the country.
Here's to hoping something electronic failed & not rodent damage.
Thread Starter
Team Owner
Joined: Mar 2014
Posts: 21,631
Likes: 1,144
From: Below the bottom of Berby Hollow, NYS
Parked in a barn?
Given nature of code, wiring damage due to mice?
Can be hellacious locating damaged line(s) since it's a random location unlike known/documented chafe points.
Evidence of chewing @ harnesses etc are obvious tells, pray it isn't under dash.
But if inside a nest somewhere is in play, also.
Been down this road twice, living in the country.
Here's to hoping something electronic failed & not rodent damage.
Given nature of code, wiring damage due to mice?
Can be hellacious locating damaged line(s) since it's a random location unlike known/documented chafe points.
Evidence of chewing @ harnesses etc are obvious tells, pray it isn't under dash.
But if inside a nest somewhere is in play, also.
Been down this road twice, living in the country.
Here's to hoping something electronic failed & not rodent damage.
Hope you get it figured out soon and cheap.
Le Mans Master
Joined: Aug 2007
Posts: 8,735
Likes: 412
From: WV
Bruze, do you know anyone with a Tech 2 unit, it may help isolate the problem farther.. With a Tech 2 you can run scans on different areas to help narrow the problem down.Also may want to erase the codes and see if they come back, they may not..... WW
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Last edited by WW7; Aug 21, 2018 at 10:45 AM.
Thread Starter
Team Owner
Joined: Mar 2014
Posts: 21,631
Likes: 1,144
From: Below the bottom of Berby Hollow, NYS
I'm pretty clueless about modern cars and scan tools. The manual with mine said to be careful about erasing codes, something about "Freeze Frames," and "manufacturer specific data," none of which means anything to me. Is there a real reason why I should not erase them and see if they come back? I originally bought this because I had tranny problems with a 2011 truck I had, and I do remember erasing codes with no ill effects. But the electronics in this car scares the crap out of me.
Not sure if this helps with diagnosing or not, but FWIW: Sunday I drove about 25 miles, made two stops a short distance apart, then drove 35 or so miles back to the local "watering hole." When I left there is when the light came on and no, I wasn't drunk, no burnouts, no wild women distractions.
Pro
Joined: Jul 2016
Posts: 547
Likes: 27
Check battery voltage first, then check all fuses in both boxes, pull out and reinsert a few specific ones that are related to the modules to check for corrosion causing a bad connection.
Have you done anything to the car recently, changed any part, replaced anything, installed anything, got anything wet, or had anyone work on it? If so that could help point you in the right direction.
Finally, you can clear codes without causing any issues, just remember to record all the codes before erasing and see if they come back. You might get lucky.
Have you done anything to the car recently, changed any part, replaced anything, installed anything, got anything wet, or had anyone work on it? If so that could help point you in the right direction.
Finally, you can clear codes without causing any issues, just remember to record all the codes before erasing and see if they come back. You might get lucky.
Instructor
Joined: Nov 2017
Posts: 198
Likes: 48
From: Dallas, Texas
Good luck, Bruze. I hope you find the problem and a quick solution.
My mechanical skills are close to zero, so problems like this get my attention bc Im sure that at some point I will encounter this problem or something similar. I also have an 07, and wish I could contribute.
Following....
My mechanical skills are close to zero, so problems like this get my attention bc Im sure that at some point I will encounter this problem or something similar. I also have an 07, and wish I could contribute.
Following....
Thread Starter
Team Owner
Joined: Mar 2014
Posts: 21,631
Likes: 1,144
From: Below the bottom of Berby Hollow, NYS
Check battery voltage first, then check all fuses in both boxes, pull out and reinsert a few specific ones that are related to the modules to check for corrosion causing a bad connection.
Have you done anything to the car recently, changed any part, replaced anything, installed anything, got anything wet, or had anyone work on it? If so that could help point you in the right direction.
Finally, you can clear codes without causing any issues, just remember to record all the codes before erasing and see if they come back. You might get lucky.
Have you done anything to the car recently, changed any part, replaced anything, installed anything, got anything wet, or had anyone work on it? If so that could help point you in the right direction.
Finally, you can clear codes without causing any issues, just remember to record all the codes before erasing and see if they come back. You might get lucky.
Okay on clearing the codes. For four years now I know I've been running on fumes, I knew at some point an electronic problem like this would pop up that I knew nothing about fixing or diagnosing.
A guy a few miles down the road is an old gearhead (my age) and he's got an old ratrod in front for sale. It's a '30s-something, just primered. Every time I drive by it it tempts me -- at least I know how to fix it.
Good luck, Bruze. I hope you find the problem and a quick solution.
My mechanical skills are close to zero, so problems like this get my attention bc Im sure that at some point I will encounter this problem or something similar. I also have an 07, and wish I could contribute.
Following....
My mechanical skills are close to zero, so problems like this get my attention bc Im sure that at some point I will encounter this problem or something similar. I also have an 07, and wish I could contribute.
Following....
Burning Brakes
Joined: Jun 2005
Posts: 913
Likes: 129
From: Toronto
Control Module Communications Bus Off is code U0073....It may be the connectors under the passenger foot well. could be loose...Take a look and re-seat them. You can erase the code with no issues with a scanner. See if it comes back
Last edited by crusher1; Aug 21, 2018 at 09:24 PM.