Hi All,
I have a 2004 C320 Sedan that we occasionally bring it to a mechanic to have him "reset" the transmission computer to stop a jerking it's being doing for quite some years now, and for some reason, this guy has been the only of 2 mechanics to be able to access it and reset it and the issue goes away for a few months. But he says the time will come when it may not accept a reset anymore, so we are rolling with it until then. He suggests some "body valve" issues in the transmission.
Fact of the matter is that we haven't been able to bring it to him since symptoms reappeared, but a week or so ago, one day in the afternoon while my wife was city-driving for a while, the ESP light came on, lost power and had to roll to a safe spot, turn the car off, wait a while, and turn back on to find out that ESP light went off and issue disappeared. This happened to her on that day 3-4 times, until she was able to arrive home and park it
Last Saturday I brought it to the mechanic to check the ESP issue since it was a new thing, and to "reset" the transmission. But after hooking up all his computers -he has a couple that uses to solve issues, he wasn't able to access the right modules and kept saying there was a comms issue to most modules -I think he could only connect to the engine's at that point.
​​​​He said battery was OK, so discarded issues there; he checked all fuse boxes -side dash and under hood and found no issues there either. He did mentioned some cables showing some off readings but he seemed not to care much about it and moved on to check other things. Then mentioned that possibly the "Control Gateway" (CGW) may be faulty, but needed to rely on someone else to have that looked at closer and have it repaired or swapped if necessary.
At the end of the day he wasn't able to determine the reason for the ESP light to came on since he couldn't access the right module to pull off the memory; he couldn't reset the transmission because couldn't access the right module. So until he could regain communication with the CGW, there's not much he can do to diagnose any further. Keep in mind that in previous 2 visits he had a hard time accessing the transmission module to reset it, but after tinkering for a while with a couple different computers he was finally able to, but not this time.
He also had a hard time determining where the CGW in this car is, since it is not where diagrams tells him, he suspects it is part of the ignition switch, so it requires dismantling dashboard to access it.
So off I went to wait for his call to come back when ready to check the CGW issue, and on my way home ESP light came on twice and experienced same issue as my wife -loss of power and had to pull aside to turn off and back on. I decided to turn off ESP after second time and was able to drive home without it showing up again - it is a pretty long drive. After that I've being doing that when needing to move around, unsure if right or wrong -mechanic says it should be fine as long as issue doesn't come on and let's me drive until we get it solved.
In the back of my mind I want the issue to be battery related, so today I drove to AAP to have the battery checked, they used a "modern" needle tester and said it was GOOD. Then I went to an AutoZone and they used a "digital" tester, which also measures crank power, and said it was BAD. Since I know these cars kinda act up when battery is faulty, I'm just wishing that replacing it will solve some of the issues. It was initially bought in 2021 and I'm sure I had it replaced before the 3yr warranty expired, so actual battery may be 1-2yrs old, not that old to be replaced
I'll appreciate your feedback regarding the battery, ESP light & CGW mentioned, thank you all.
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I had a similar problem on my C55 AMG. What fixed it was cleaning and tightening the ground near the ABS module on the driver side of the engine bay. No problems since.