Well............... Its either the wires and connections from the switch (in your case the resistor/s) OR something is wrong with the BCM.

Ive seen more than I care to count CORRODED and water damaged BCMs Ive also see BCMs with **** poor solder joints.

Disconnect the Battery neg lead and remove the BCM. Pull the board out of the aluminum box and use a jewelers loop and inspect the solder joints areound that connector.

Look for corrosion or poor solder joints:

Here is an example of corrosion at one of the input connector terminals where it solders onto the board..



Give that a whirl. NOTE!!! Be careful.. All the boards are ESD Sensitive. Don't static ZAP it.

BC

 

Wow. I just picked up a C5 with 93K. It has a lot of the issues spoken about here - traction control, ABS, I don't have working TPS either. I'll have a lot of reading to catch up on.

Just wanted to say thanks for this great info!

 

Well I have my car finally finished with the help of this incredible forum, here is a list of the items that presented themselves after I took ownership.

1. Headlights turned on no taillights - fixed by replacing combo switch

2. Left Headlamp would not always come fully up or go down - fixed by replacing plastic gear with brass.

3. Traction Control/ABS - Took an exhaustive amount of diagnosis as well as serious knuckle rash but was finally able to clear all codes by replacing of all things the complete under-hood fuse box. There was something broken inside the #52 maxi fuse underside location.

4. Oil Pressure reading off the charts - Replaced plastic oil sender with a brass one

5. Fuel Gauge - would read all over the map. Ran some sea-foam through the system and works like a charm

6. Gauges - my gauges would act like there was a demon inside my electrical system. I cleaned every bloody grounding point on this car and all weirdness has left the building.

7. Brakes - while there was plenty of braking power there was a constant annoying squeal every time I touched the brake pedal. Very attractive on a such a beautiful car. Ended up replacing brake pads and rotors.

8. Service Column Lock - at this point I considered arson but after reading the tech postings I installed a CLB and this annoying warning has since been exorcised.

I'm not a mechanic but after reading many many posts was able to transform a problem laden C5 into a very reliable and trouble free ride. If I can do this there is hope for all, just spend the time needed to read and research. The great thing about this forum is that pretty much anything that can happen has and a fix has been documented.

Thanks Again to all that helped.

 

That's great to hear!

I was really afraid I got stuck with a lemon, but it doesn't have quite this many issues. I plan on going though one by one and knocking each of these problems out.

Oh, what pads and rotors did you select?

 

I just grabbed the best ceramic pads I could find here locally. The Rotors I got off a dealer online. I'm not sure of the manufacturer but do know they where from quality material. Good Luck!!

 

Bill....

I have a 2002 Z06 and I've been having codes P1571 and U1040 on for almost 2 years now. I had multiple people look at the car and went through multiple EBCM's (repaired and purchased refurbished ones as well)

I checked ground connectors 101 and 102 in your drawing and they look in very good condition with no sign of corrosion. I also took out all the fuses that have to do with the BCM from under the passenger side dash and left them out for a minute. Some people said that fixed their problem, but no luck.

Is there anything else that you can think of that might help me?

If anyone else has any solutions please let me know.......thanks.

 

I think I have found the electrical problems with the C-5. The Gremlins are coming from the Windshield Wiper Pulse system. There are 3 water drains under the windshield wiper motor which have rubber nipples inserted in them. They need to be cleaned on a regular basis. What happens is that when washing or rain happens the wiper motor basin fills with water and gets the pulse system wet. This system is connected with all the grounds that we are getting codes for. To clean nipples reach under break boost and squeeze the nipples and pull out then clean. I'am going to replace the wiper motor $72. Hope this helps.

 

Bill , Would this issue be the reason my battery dies in three days of non use of my 2000 convert?
Brandoni

 

Bill,
Wanted to report a minor success from reading this incredible thread.
My 2002 Coupe was throwing a series of Codes almost every time I started it up.
Same five codes ALMOST every time:
PCM P1571
TCS C1277
BCM B0432
SDM U1040
IPC U1040
Plus the occasional "Service TCS soon" warning.

Somewhere in the 73 Pages of this thread I found someone who had the same problem and the suggested cure was to clean the contacts of the Ignition switch module. That is a daunting task for a guy who is not a mechanic or electrician, however, having been married for 45+years, I can follow directions. With help of many other thread suggestions, and a UTube video of how to remove the console to get to the ignition, I was able to complete the task in about 2 1/2 hours. Several starts later, still no codes.
Fingers crossed for a little while.
thanks,
Hapiduffer

 

As our cars age,,,,,,, the ignition switch issue will become more and more of an issue.

Glad that solved your issues! See,, wasnt that easy??

BC

 

Hello dear gentlemen

I am writing to you from Europe to Hungary

It would be two problems


* have a nice c5 95 silver, beautiful factory LED taillights do not work but I changed the megfellelöen and Electrical drawings would be needed and the entire electric car drawings are well done and I would like to renew

* the other is that I want to revive the factory claret and black seats I would not change her plain black dye if someone needs it I want it to black mail I think can be solved
This reminds me of the sudden capita email address Jaffa 12@freemail.hu

Thank you for your help in their accident-free way for everyone

 

I'm sharing this today to give KUDOS specifically to Bill Curlee and Tom aka "Hapiduffer"(a couple of posts above) who have posted in this thread. Their words & posts helped me fix all my issues with my '98 A4 coupe w/81K miles on the clock.

Beginning in early 2012, I started getting the following DTC's on a consistent basis, which left my car without the HVAC and F45 electronic suspension working...as well as ABS and Traction Control warning lites on the dash display. At first the problems would come and go, then the functions quit completely last summer. I even cleaned all the chassis grounds, but that didn't solve my issues.

10 PCM
P0134H-C
P1571H-C
P1631H
P1644H-C
P1652H-C

28-TCS
NO COMM

38-RTD
NO COMM

60-IPC
U1040H

99-HVAC
NO COMM

A1-RDCM
B2265H

BO-RFA
C2100H

40-BCM
B0432H-C
B2723H

For over a year, I've been studying my GM service manuals, reading this post when I could and asked every C5 owner at car shows if they had similar issues with their cars. I definitely learned the most from this post started by Bill Curlee. Finally this spring I talk to an owner who said his HVAC quit on him and he changed the ignition which fixed it. I also had a local non-dealer technician try to diagnose my issues but all he recommended after 1.5 hours of labor, with my assistance, was to r/r the EBTCM and BCM. I was not comfortable with that nor just throwing money and parts at my car without really knowing.... so I kept researching.

Then a week ago, I read Tom's (Hapiduffer) post above and Tom's isssues sounded like my problems, but instead of cleaning the ignition contacts as described by Bill Curlee that Tom did, I opted to just buy a new unit....from AutoZone for $89. I still wasn't very confident in doing this repair so I PM'd Tom and he called me within a couple of hours and convinced me I could DO IT! I'm 69 with bad knees but with a lot of mechanical experience, and have always done my own service on my Vettes and Blazer but I was sure nervous about this ignition repair and not knowing if it would really fix my issues. So finally...last Saturday I gathered up all my notes, ignition pics (inc.instructions from Vette Essentials) to r/r the console and IP center trim.... and headed out to my garage and disconnected the neg. battery terminal...and spent about 3 hours on this project. I took my sweet time so as to not break plastic parts and probably spent most of the first 1.5 hour learning the removal technique for each of the electrical connectors that had to be taken apart. Seems each one had a different method of removal...well maybe not, but it sure seemed like it! Once I actually got to the ignition, it was easy from there on, and I had it replaced and all the trim pieces carefully back together in 30-45min. I reconnected the neg. battery cable and started my car...praying it would be back to normal again.....and it was!! I think I was actually surprised to NOT see that damn ABS and TC warning lite not ON, but to see my climate control HVAC temp reading again was the best thing since my a/c etc had not worked for over a year. After several test drives over the weekend, everything worked like a champ and it feels like I've got a brand new C5 again. What a great feeling and relief that it's normal again.

fyi....I took apart my old ignition on Sunday and 2 of the 5 contacts were quite burnt or corroded.....just like the points in my old '56 Chevy distributor used to look like. I'll clean them and re-arch the tension in the spring arms and just keep it as a back up for now.

THANKS again to BILL & TOM .....and all you other owners who have had posted in this thread about your own electrical issues.

If I can do this.....you can too.

Fix

 

Bill Curlee, you are the man! Thank you for all this great information.

Your sticky on the ignition switch has solved several electrical problems that have had me baffled for months. Several of the contacts in the ignition switch were black and pitted (130k). Now she starts properly, doesn't cut off, maintains a 14v charge, and no more ghost codes. I am one happy C5 Z06 pilot today. Thank you, thank you, thank you.

 

Im very happy that you guys are finding the information helpful. As always, I and always willing to help.

Bill

 

This is a great thread! I have a 2001 Coupe with about 21,000 miles. I have been having a heck of a time with a strange engine noise and, lately, the engine continuing to run after turning the ignition switch off. The following is thesequence of events:

1. About 2 days after driving through about 6" of standing water my check engine light came on.
2. After 3-4 days decided to have codes checked and, on the way to the shop, noticed the Check Engine light had gone out. Great, or so I thought.
3. About 2 days later I started the car and there was a loud noise coming from the right side which sounded like I had something caught on the fan blade. Sounded really bad. Turned engine off, then back on and same noise. Drove it out of parking lot, "punched" it and noise went away.
4. next morning same noise, turned engine of and back on and noise was gone.
5. After 3-4 days of this I finally took it to the dealer but he couldn't find the problem because the noise would not occur even though he kept it for three days. I was particularly concerned because on the day I took it to the dealer, the car tried to continue running even after the ignition switch was turned off. It seemed like the right bank of cylinders tried to continue running.
6. After taking it back from the dealer, car seemed fine for a couple of weeks and I thought the gremlins had died.
7. No such luck. Got in car this morning and noise was there. Now, when I tried to shut the engine off, it kept running like it was possessed though again it was on the right side. Sounded like it was "diesling" like the old days with poor fuel but I always use 93 octane. Drove the car a few hundred yards with noisy engine, tried to shut down again and no luck. Finally, I just turned the ignition back on and gunned it. Noise went away!!
Drove car and no problems restarting, etc.

Any ideas? Could it be a faulty ignition switch which tries to keep the starter motor engaged initially and then does not entirely turn off when I turn the key off?

Any help greatly appreciated.

 

The problem has been there for three years. Horns don't blow, then with no apparent change, they blow weakly, or one horn blows weakly, or when I use the fob, the horns blow weakly, or one horn blows weakly, horns blow when I press the steering wheel center, but blow weakly, or only one horn blows, and then they stop working and the horn doesn't blow when I lock with the fob. Or, one horn blows barely audibly when I lock with the fob.

Then they stop working. No horn button, no fob, no noting makes the horn blow. .they start working again as described above.

The interval between not working and working and back to not working is random, sporadic at best.

Dealer said the horns were bad, replaced them, horns worked for a few days then stopped working. Independent garage said relay(s) were bad, replaced them, horns worked a while then stopped. Then they started working again feebly then quit.

I'm about $%^&* tired of this but can't figure out what is going on. Does this sound like a membrane switch issue? How can it be intermittent if the horn swith membrane is bad?

Any ideas on what to do are more than welcome.

Charlie

 

My HUD does not display. If I look down in there is moves up and down but does not light up.

Any suggestions? Is there a backlight bulb?
How do you remove the unit?

Thanks for your help in advance.

 

CHARLIE

Your problem is most likely just a bad ground. Your main horn ground is chassis ground G-102 and that is located directly reward of the passengers head light assembly. Its on the top of the frame and bolted to a stud with a 10mm nut. Dont just remove the box from the stud. You have to disassemble the ground assembly. There are male and female pins inside the connector and there lies the corrosion. Its a good idea to also clean G-101 and it is in the same place but on the drivers side of the frame.

G-102: & G-101 look like this






Disassembled:






The other horn ground is G-201 BUT,, I doubt that it is the issue.

Bill

 

Anybody? Should I just buy a new HUD?

 

The HUD projector image looks just like the image you see in the windshield. Its a vacuum florescent image that gets projected on that mirror and on to the windshield.

You need to make sure that the HUD is properly plugged into the the IPC. Remove it and inspect the connections.

BC