'97 C230, CEL Code P1747: Urgent?
 

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,

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.

Update
 

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. . . .

Update: 722.6, P1747 CEL code
 

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,

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.

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.)

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.

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.

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.

Other indie shops? in NO?
 

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.

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.

Update 3: The Dealer
 

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"?

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?

Post the codes.

The code isn't on my receipt, but the service advisor said that they were getting the same one I had before, P-1747.

How did this all play out? Find a good shop? I am interested because I am looking for a shop in The New Orleans area for my mother's 1990 300e. Idle is up and down at stops lights.

Maybe a dirty MAF could be causing the erratic shifting.A new maf(amm)improved my shifting.Try resetting the ECU also.

Upshot
 

The C230 has been behaving fine the last ten days or so. It stuck, then slammed into gear the day after the dealer visit, but has been fine since then (!)

The advice I've gotten from two independent shops here, one being the guy I've gone to for more than five years, is just what the dealer said: Until they can reproduce the problem, they can't be *sure* replacing the controller would fix it.

300B: If it's the MAF, wouldn't there be other driveability problems, poor gas mileage, etc.? My mileage is tip-top.

In the meantime, I'm having the shifter bushing(s) replaced to solve a nasty rattling I've been hearing in the cabin on ripple-bump roads. Seems to me I saw a post here that suggested that, just possibly, if the shifter isn't making the right contacts, the transmission could get confused and not know what gear to go into. Maybe that'll help, or even solve, the issue?

Daveuz, I don't know the board rules about posting the names of shops outside the Good Shops section. Have a look there; I've posted the contact info for my regular mechanic. Or you can PM me.

This problem is easily resolved. Do a search on throttle position sensor; use my ID if you have to. You basically have to clean it with some carb cleaner - lots of it, maybe 1/2 a can. Then you hose it down with some WD40 and the up/down idle will be gone. It worked for me when I first bought my 300E and it had the same problem. Hers (1990) has the same engine setup and everything. Give it a try.

Just wanted to point out the C230 and 300E have completely different engines, so the fix for the C230 wouldn't apply.

My driveablilty and MPG's were good and I didn't have a code however my AMM was bad(finally got the dreaded P0170 and P0173).

A new Maf cured a sometimes hesitant and slighty confused 722.6 in my C280.:sultan:

AMM, huh?
 

Thanks for the tip, 300B. Without codes for it, however, is there any way to test to see if the AMM is bad? That's a $300-$400 part, even from here on Fastlane, and I'd like to be sure before spending. Or could I just clean up the wires?

Seen it for less,much less.

Could help alot.

AMM prices
 

I've been doing a little 'net research, and have found Bosch units for as low as $242.99 at All OEM Parts.com. Was Bosch the OEM supplier?

Are you driving it in S or W mode? I noticed sloppier, improper shifts in S mode than in W mode so I leave it in W at all times. Smooth as a button and the transmission is getting more torque.

Admiral
 

Do you have any slop/play whatsoever in your shifter when it's in "D?" Next time it's in gear, try to move it in millimeter increments toward "P" and "3," not actually clicking it into the next position, but seeing if it will move out of the "d" position and NOT pop back where it is suppose to be. Mine was doing this for a while and after the shop spent $1500 of MBUSA's money, they figured out a 3 cent screw holding the linkage to the transmission was causing jerky shifts and slippage.

BenzOnline,

I've always used S mode, so the car starts in first gear from a light. With the A/C on, I find it helps the little 4-cylinder's acceleration. The W mode is fine . . . once the transmission is out of that warmup mode where it delays shifts for a minute or so in order to improve emissions. About two years ago I accidentally set it to W, and the car acted so weird I thought the transmission was going out. But once I'm past the warmup period, you're right, it is smoother, and I guess would bypass any problem with shifts from 1 to 2, because the tranny would bypass 1 entirely.

Will_w202,
Yes, there is a small amount of play, enough to rattle on ripply surfaces. The sound seems to vanish when I drive with the selector snicked over to 4: no play. I'm having those bushings replaced today, and will report.

Bushings are separate from what I had replaced. It was literally a screw or bolt. The bushings may help though......

Update, again, and a Q
 

Hey, all,

The C230 has been great and trouble-free for more than two weeks, until yesterday. I got the refusal to shift/slamming into gear symptoms again, and as I parked the car, the CEL came on. However, the car started and drove perfectly this morning -- though with the light still on.

It seems I get this problem *only* when, upon starting the car from cold, the idle is immediately too low. By that I mean, instead of first idling at about 1000 rpm then dropping down to 550 within a few moments, the car starts and almost instantly drops to 600, then 550. Almost invariably, if this happens, the car will refuse to shift correctly and will slam into gear (it feels almost as if somebody is rear-ending me!).

From what I've read here, this sounds like an air mass meter going bad. I know I need to get the codes read again. Qs about the CEL situation:

1) Can a standard scanner, such as Autozone's, pull the right code? Or do I have to go to my independent?

2) Can the codes be read with the CEL off? The light comes and goes, and I've been told that if the light is off, there is no stored code to be read. Is that correct?
.

A cheap scanner ( i.e. Autozone ):D should be able to retrieve that code.
Yes, the code will still be there, even if the CEL is not on. ;)

New info (?)
 

Went to AZ yesterday and got the same code, P1747, regarding the solenoid.

However . . .

On another site, I was sent a link to this service center: http://www.robisonservice.com/servicedep/merc_faults.asp

Their description of the code says "P1747 Electronic Gear Selector Module: Defective Interaction of CAN with control unit A1 (instrument cluster)".

I presume "CAN" is the controller unit the dealer spoke about? Anybody else have an issue like this?

Looks like you're on the right track. CAN is the area network that connects most of the systems of the car together. I would think that a problem with a gear selector thingy would be causing some odd trans behaviour.

p1747
 

I just got this code today and it occurred when the third brake light was out due to spark at the connection and by sticking it to have it go on it cause a short and the fuse went out, fixed the light by soldering a wire and engine light was on p1747, I clear it and that all. The car has 166500 miles and never had a problem with transmission. Hope that can help .