donald4972

Sorry for longwinded, but trying to give a picture of my issue as best I can:

I have a 2003 C5 base coupe. A4 transmission, with about 55,000 miles. Had it for several years, and love it. Three years ago, when I still lived in Illinois, I drove to Tennessee. Got stuck in a rain storm so hard late at night, I had to pull over for poor visibility. After the storm moved on, my C5 showed the message 'service active hndlg, service traction sys and service abs'.
Since I was far from home, i just continued on to my motel, about 50 more miles. The next day, a sunny nice weather day, I went out and started the car, and NO message. Problem gone, seemingly. I finished my trip without event.

No more codes for a long time, well over a year. This car is a daily driver, and runs flawlessly, always. Except for this Code C1242; which I wish to fix.

About six months ago, just after washing my car, I got the same messages, and same code (C1242). Now I suspected a grounding issue, as I'd been reading up on this code to try to understand what's going on. I'm only mildly mechanical, so I thought to take it to my mechanic soon. But, the next day, the message was gone. Car fine. Again, I figured moisture got in somewhere, and then evaporated, or something like that.

I quit washing my car, months ago. I use the Chadwicks stuff, and almost never spray water on it. But, I still put a blanket over the wheels, and spray them with water lightly, then clean them. I put a barricade of sorts, over the wheels, so no water gets on the 'painted surface of the car', when doing this. So, after washing/cleaning my wheels, I got the same message issue with the DIC. The ONLY code I have, is C1242, in the TCS module. At times the code shows history, and at times it shows Current. All other modules always say 'no codes'. So now, also; I'm thinking it's a ground, somewhere close to one of the wheels where I sprayed some water to clean brake dust off.

This time, the DIC messages did not seem to go away, and continually flash, and dash icons lit up. Of course after a few days, it cleared. I think this has something to do with 50 or so cycles, and no further issue, the fault clears (or something like that, I read ???). In any event, it cleared. All the while, during these times, the car drives perfectly; and there are NO other codes, at all.

I've been trying to read threads on the Forum, to understand this, and it seems related to bad ground. With previous history of issue after washing or rain storm, maybe this is a ground that needs a very good cleaning and reassemble.
So, I had occasion to take my car to my mechanic friend (who owns C5 Z06 Corvettes, and is familiar with C5. We went through all the grounds we could find and cleaned them. Read all of Mr Currys info, and pictures of bad grounds, and cleaned all of these. Finally again, the car ran perfectly, no codes, for months. Thought we had it.

Then last week, I drove my C5 up the California coast from LA area to north of San Francisco, over to Lake Tahoe, then home.
On the 3rd day, started the day getting gas. No codes. After filling with fuel, started to drive away from gas station, and now have the same messages again, and still with only the C1242 code. No rain or car wash, or anything like that. Damn.....

Drove the rest of the trip, about 3 days, with messages flashing, and or the dash icons lit up. Then, on the last day while driving home, and after rest stop; codes cleared, and drove home. I'm guessing enough cycles again and it reset (???). The next morning at home, after it sat in the garage overnight, went out to start the car, and messages/code returned.
Next day after that, no code again, and no message. This time, could only have been 4 or 5 cycles of starting and driving, then cleared.
So now we are surely 'intermittent' with this issue.

When I read every Corvette forum thread I can find on this, some guys have a whole bunch of other codes with similar problems. I only have the C1242.
So I still think ground wire somewhere is bad, or loose, or still corroded making partial contact, intermittently..... But, what do I know?????? The first few times I got the code, it seemed to correlate with after rain, or car wash; moisture. Last times, not so at all.

Most recently (Monday), we got the car back up, and took apart the two (one large, one small two wire) connectors to the EBCM. We cleaned them, and put them back together. The large one, did show some white, what looked like corrosion, in the upper left corner. Thought we had it! We cleaned this out really well, and put it back together, after also cleaning the smaller connector, as well. But no, still had the DIC messages, and code C1242 H C.
The code reader we have, sees the C1242. It resets it. And then the open ground comes back, a second later. I can clear the DIC, and the Code C1242; the code clears, the two lights on the dash go out (the icons for abs, traction); and then just a second or two later the code comes back and the icons on the dash light up again.

We also pulled and cleaned all 4 of the wheel speed sensor connectors.

We're out of ideas, and thinking it may be time to send EBCM to absfixer, or similar repair service. Is it time for this?

Would appreciate any other thoughts, or advice to help figure this out? Does ONLY Code C1242 indicate that the usual failures of the EBCM will cause this lone code?
Since my C5 always and only gets the one code (C1242), is that telling of anything peculiar, or directing me to 'one' place to search for the problem? Is it time for absfixer ? We've gotten as far as we can, and will appreciate some direction from more knowledgable guys.

The only mod, really, is that I had it SuperCharged by (A&A), earlier this year in February. A retirement gift, from me to me. But the issue with C1242 was ongoing intermittently at least 3 years ago, and subsequent to the SC install. So I'm as certain as I can be, that had nothing to do with this issue. There were no codes for months before, and after the SC install last Feb.
I also put a new Die Hard battery with 850 CCA in the car two years ago, and it seems strong all the time, so I don't think weak battery is an issue here. When the old battery that was in the car when I bought it started to fail, it happened rather suddenly, the DIC threw some codes, and all that cleared up when I got the new battery, and never missed a beat since, or failed to start, since then.

Thanks, and appreciate any help, suggestions or advice.
Don

Castor

Old problem, but it seem that I found the resolution.

Also was having service ABS / Traction / Active handling with only C1242. Was going to make same dances with EBCM wiring.
But noticed that - if to move a key with cylinder in ignition before starting - issue is appearing and disappearing.
Played a bit and, got 100% correlation.
Removed central bezel, and tighten loose bolts, which are holding ignition lock.
Have no idea how it works, but problem gone now.

Let's see for how long...

PS: In any case ordered new ignition lock, as cylinder itself is feeling loose. Will replace when get it and advise.

Alley Oop

You might want to check this as well...There are 2 electrical connectors in the door wiring accordion. The female pins may be loose which could cause your electrical issues.

There are two connectors, one contains pins and one contains sockets, you have to use a small flat blade screwdriver to expand the metal tabs of the sockets

Castor

Thanks.
Is it in the door or under the dash ? any PN to search fro pictures / precize location ?

Thanks in advance.

oelarse

I think Alley Oop is refering to these sockets in door hinge area

Alley Oop

Just where oelarse indicated.
Cheers,
Mark

GettnBetter

Check the ground connection on the battery. If ground isn't clean, nothing on the car works

Castor

Thanks, had never noticed socket there, will check !

Castor

This had been checked first. And most of grounding points - wherever in reach had been checked too.
Seems that my issue was in grounding of ignition lock - while sounding funny