Electrical Issues

Having just fought intermittent electrical issues on my 2003 Suburban Z71 I thought others may benefit from my experience and seeming simple solution.

The background on the problem is that my 2003 sub (82K miles) experienced what seemed to be a major system anomaly one day. I had just crossed over a slight bump when the chimes started going off, the door locks started cycling, the dash lights flashed, the cruise control became inop, the average miles/gallon reading went from 15.2 to 8.1, the ABS light and the parking brake dash light came on, the message center started throwing error messages of all kinds. The engine went into reduced power mode but continued to run. As suddenly as it started everything except the dash lights for ABS/parking brake stopped. I drive straight to my mechanics shop where it was hooked up and threw out two pages of error codes.

We decided the problem lay with the computer so it was decided to replace it. It took five weeks to find a correct ECU/ECM. All the units send to the shop had the incorrect code on the back and did not accept the program for my VIN. It seems the 2003 model is a bit of a red-headed step-child. The electrical system was redesigned for that year from 2002. The 2004 system was also changed which leaves the 2003 electrical architecture as unique.

After 5 weeks of fruitless effort the original ECU was sent out and wiped clean. It then was reprogrammed which it took. It was then re-installed and after a few drive cycles things appeared to be resolved. Key word is "appeared".

The original problems would return from time to time. Specifically when the vehicle experienced a sharp jolt due to a large expansion joint or pot hole.
The mechanic was at a loss. I also took it to the dealer who had replaced the gauge cluster back in 2005. The cluster checked out fine. They suggested letting them run their diagnostics for $100 but they could not promise any solution. They also confessed they had never heard of this issue(s) before.

Then one morning the truck would not start at all. Completely dead. I pulled the battery and had it tested. It came up as good but only had 4% of the charge. After recharging and re-installing it, it still would not start and in the morning the battery was dead again.

I then spent several days researching the issue on the web. I was not the only 2003 owner having similar issues. I found one thread that pointed to the Body Control Module (BCM) which the dealer wanted $301 for plus $107 for installation. Again, no promises this would clear the problems.

I also found a thread identifying a battery drain issue covered by a recall. The recall number is 02066. If you are having a problem with the battery you might check to see if your VIN is covered by this. It was 2003 specific. My truck was not covered.

Finally I found a thread that described my exact issues. The solution was not posted so I contacted the person directly. His apparent solution defies logic in its simplicity.

His solution:
There is a thin ground wire located on the back side of the engine block. It is on the passenger side and you have to remove the plastic engine cover to find it. The connection at the block is a bolted ring lug. This connection was loose on the Tahoe of the guy giving me this information. He moved the connection to terminate with the braided ground strap that connects at the firewall on the drivers side of the engine. He claimed this solved all his problems.

I checked the ground wire on my truck and it was tight. I removed the bolt, cleaned the surfaces and re-installed the ground wire. I was recharging the battery during this time. I also checked all the other wires I could to ensure none were loose. The wire bundles I did come across in the engine compartment, under the dash and in the steering column I moved around as best I could on the chance there may be a chaffed wire somewhere causing a short.

I then re-installed the battery and placed a multi-meter between the ground on the battery and the ground cable with the positive cabe installed. This would show if there was a drain on the battery. The meter showed a constant drain of 3-4 milliamps which is very little and would not drain the battery.

After completing the battery hook-up I tried to start the truck and found it started right up. This was done on 2/21 and the intermittent electrical gremlins have not returned. After starting the truck I drive it over some of the roughest roads in the area trying to make it hiccup again but it did not repeat itself. The truck has started up each time since then.

I know it seems questionable whether one small ground wire/connection could be the source of the problems but the results cannot be argued. If you are having similar issues with your truck you can't lose looking at this solution before tossing hundreds of dollars to your mechanic or more to the dealer.

I hope this helps someone out there. If it does let me know here.

If not for the drain I would say you found the problem with the ground. However with the drain and the problems you are having the BCM would be the cause. This is a common problem.

www.proautoelectricinc.com (http://www.proautoelectricinc.com)

your problem is very common,,,incompentent vehicle repair tech's when it concerns electrical problems...

when ever several non related electrical devices fail it is the grounds that need attention......REPLACING THE COMPUTER !!!!its always the computer because they don't know what there doing....

since your vehicle had this issue ...remove the battery neg terminal and clean all body ground points you can find...

the frame rail next to the fuel tank and the frame rail under the driver feet area is are areas of high probability of poor grounds...