'97 C230, CEL Code P1747: Urgent?

[Benzadmiral]

Hey, all,

For the last week the 722.6 transmission has been acting a little oddly. I'd brake sharply, and then if I tried to accelerate immediately, the transmission would seem as though it were not engaging. I'd give it gas, and then it would shift properly. This didn't happen if I braked sharply and then waited a second to accelerate. I was planning to have a fluid and filter change done this month; it's been about 4.5 years and 35K miles since it was done at the dealer for the previous owner.

Today, as I sprang onto the Greater New Orleans Bridge at rush hour, I braked sharply . . . and felt a jerk, and my Check Engine Light came on!

The car seemed to drive normally, though. I went to Autozone to get a quick code check, and the scanner came up with P1747, "Pressure Control Solenoid 'A' short circuit." The CEL was out when I restarted the car after this, and didn't come on during the 3-mile drive home. Again, the car seemed okay.

I've done a search, and found nothing on this topic. Any ideas? I'll call my regular Merc independent tomorrow, Friday, but he probably won't be able to take the car until Tuesday or so. In the meantime, I need the car for errands and to get to work. Will I be okay until next week? Are we talking about major tranny work?

TIA,

[Michael K]

Get ready to spend ~$1,000. If I remember correctly, it's to replace the "valve body." The good news is the $1,000 cost includes new fluid and filter.

[Benzadmiral]

Hey, Michael,

Don't surgarcoat it, boy, gimme the straight dope!

Seriously, maybe I've been on borrowed time. Before I bought the car, I was aware, through research here, of the possible problems with the 722.6. The dealer service history indicated about $950 of work -- "customer complains trans not shifting properly" -- at 49,000 miles. So I was sure the fluid had been done, and possibly the software upgrades. I'll stop at the local dealer tomorrow and see if somebody can tell me from the printout codes what actually got done.

The CEL didn't return during the 9-mile drive to work this morning, and the car behaved perfectly. My aforesaid independent was reassuring, saying I'm fine to drive the car until Tuesday. He works on these 5-speed boxes all the time, he says, and he's always tried to *save* me money on this car and the W126, so we'll see what we'll see. . . .

[Benzadmiral]

Hello again, knowledgeable folks,

The 722.6 in the '97 C230 (87K miles) is still acting poorly at odd intervals, usually about once a week, for the last 6-7 weeks. About a month ago I had my regular independent guy change the fluid and filter, using the MB fluid of course, and he said he saw no shavings. He thought the filter hadn't ever been changed, which is odd, given the service MB did on it 35K miles ago (see above).

The problem has continued to crop up: a refusal to shift out of 1st for several minutes when the car is warm. Sometimes restarting the engine helps. Otherwise I can drive, sort of (20 mph gives 3000 rpm!), and it usually "snaps" back into the proper gear after a few minutes. The CEL doesn't always come on when this happens, though.

Anyway, my independent researched the P-1747 CEL code. Alldata gives instructions to check the ETC (Electronic Transmission Controller?) and the CAN (Controlled Area Network?). This is not something that Kevin can work on; his suggestion is to go to the dealer.

Before I go, I'd like to see if anybody's had a problem like this. Is the controller something that can be replaced without requiring an entire new transmission? Is the network something that can be reprogrammed?

I have his printout from Alldata, and can scan and post it tomorrow at work, if that'll help.

TIA,

[stevebfl]

Unfortunately you probably have the early design valve body that had numerous problems. One of those problems was a conductor plate (the internal wiring harness) that had unshielded leads. Accumulation of normal wear debris can give electronic glitches to these. The plate also holds the temp sensor and speed sensors.

While the plate is less than $200 the valve body is available from MB for an outstandingly low price (less than $400 last one I used). The valve body includes the plate and all the solenoids so it makes a hugely better deal, except that for the early models one will also have to replace the controller.

Again, experience is a valuable commodity in the one you pay to fix this.

[Benzadmiral]

Thanks, Steve,

That $400 parts cost sounds a lot better than a new transmission! Any idea how much to replace the controller too? Is this a one- or two-day job, generally speaking? I have to rent a car while this is going on, and so I need to take this into consideration as well.

In your experience, once this is done, will the transmission (with proper fluid & filter service) be good for a long time? And would you expect an authorized MB dealer to have the experience necessary?

(Gah, this has been a lousy year -- in April I was rear-ended -- and it's only half over.)

[stevebfl]

The code you got is probably coming from the ME controller as an emissions code. The transmission has a world of diagnostic capability built into the software and available with a real scanner/diagnostic computer.

There is a lot of risk in the 97 trans. There were significant mechanical mods made that changed the planetary support and one way clutches. I have seen many go forever but the risk is significant that a electrical repair now might do nothing to long term mechanical risk.

I would look to make the repair with the conductor plate if it answers the issues, the control unit is rather pricy.

[Benzadmiral]

Originally Posted by stevebfl

. . .

There is a lot of risk in the 97 trans. There were significant mechanical mods made that changed the planetary support and one way clutches. I have seen many go forever but the risk is significant that a electrical repair now might do nothing to long term mechanical risk.

I would look to make the repair with the conductor plate if it answers the issues, the control unit is rather pricy.

Oh, I was aware of the risk, from researching here, before I bought the car. I guess I (perhaps foolishly) assumed that the significant work at 6 years/49K would have included all service and updates. If that work hadn't been in the records, I might not have bought the car. And much as I love this W202, I'm not sure I want to deal with a "significant" risk of mechanical trouble in future.

We'll see what the dealer has to say, if they can get me in this week.

[Michael K]

My humblest opinion about this is a dealership's service department may not be the best place to get this resolved. They're likely to report back, "sir, so that I can get you back on the road, would you please authorize $6,000 for a whole new tranny." A KNOWLEDGEABLE independent Mercedes shop would be, I think, a better choice to properly diagnose and fix the issue. Good luck.

[Benzadmiral]

Originally Posted by Michael Kerley

My humblest opinion about this is a dealership's service department may not be the best place to get this resolved. They're likely to report back, "sir, so that I can get you back on the road, would you please authorize $6,000 for a whole new tranny." A KNOWLEDGEABLE independent Mercedes shop would be, I think, a better choice to properly diagnose and fix the issue. Good luck.

Knowledgeable? I'd love to find more than one in The Great Swampland.

There are a couple of other shops here, none of which I've ever been to, with the exception of the guy who wanted $3000 to change the timing chain and guides in the 420SEL. (What did he want to do, take the engine out and bring it home with him?)

If the dealer tells me what you suggest (which is my fear, too), I'll try checking out the shop in Kenner recommended on the Good MB Shops forum, Lindsey Automotive. I just got off the phone with him, and he does indeed work on these trannys. "See what the dealer reports," he says, "and then check with me."

I love the car. It's 90% paid for, and I want to keep it. But I can't justify paying more than half of what the car is worth for a transmission, and I can't live with the problem. . . .

We'll see what we see.

[Will_w202]

Reassurance, or jinxing myself, I was fortunate to have had CPO fixes for mine from 80-95k, including conductor plate, controller, and 2 fluid and filter changes since then. It now has 155k of mostly highway miles, so 70k in 2 years. Yes, I drive the hell out of it, and though it's highway, I give it a workout quite often, and it usually does fine, with the occasionally funny shift. I'm about to do another fluid and filter at 160k, or 40k interval. I'll see what the shop says about wear particles, etc.

[Benzadmiral]

I just heard from the dealer service advisor, who surprised me this morning by sounding quite knowledgeable. She it was, not me, who mentioned the valve body in regard to transmission problems.

Anyway, she says that they are not 100% sure of the solution. They drove my car repeatedly, trying to reproduce the problem, and of course the little gold beast behaved flawlessly (as it usually does). They have codes that point to the controller being the culprit, but she hesitates to simply throw a $1500 part at the problem when they're not sure. (I have to say I'm impressed for the first time with Benson Mercedes of Metairie. Others have told me of poor service experiences there, but so far they seem pretty sensible.)

So should I take a chance that the controller solves the problem? I'll get the codes tomorrow when I pick up my car, and I can post 'em. Is it at all possible that, if the new controller doesn't solve the problem, I could at least get my parts cost back? Or is it, "No return on electronic parts -- you used it, you keep it"?

[Michael K]

Personally, if it were me, I'd feel justified asking the dealership to take responsibility and assume the cost risk. Should they not 100% be able to tell what the problem is by the stored fault codes? My attitude is you sold this model and support the manufacture: you fix it. Have they tried to sell you a new car yet?

[Benzadmiral]

Originally Posted by Michael Kerley

Personally, if it were me, I'd feel justified asking the dealership to take responsibility and assume the cost risk. Should they not 100% be able to tell what the problem is by the stored fault codes? My attitude is you sold this model and support the manufacture: you fix it. Have they tried to sell you a new car yet?

No, they haven't tried, and that's what impresses me -- it doesn't feel like a sell job. (No "Your car is dying, sir. Can we interest you in a 2007?")

When I go back tomorrow, I'll ask just why is it that the stored codes don't give the answer; isn't that the reason for having them? What would it take to get 100% -- for the transmission to fail completely in front of the dealership?

ETA: I just talked to the service advisor. No, the controller wouldn't be returnable, so it would be a crapshoot. She explained that the controller that's in the car now was active -- despite the code that it tossed out, the unit hasn't failed -- and so they can't nail it down that the controller is the culprit. They've wiped all the codes, and so we're starting fresh.

I'm pleased that they're not being casual with my money, but does this make sense?

[Michael K]

Post the codes.