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,

__________________
* *
-- Paul W. (The Benzadmiral)
('03 Buick Park Avenue, charcoal/cream)
Formerly:
'97 C230, smoke silver/parchment; '86 420SEL, anthracite/light grey; '84 280CE (W123), dark blue/palomino

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.

__________________
Michael

1988 300 SL (5 Speed)
1994 E320 Wagon
1997 C230

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. . . .

__________________
* *
-- Paul W. (The Benzadmiral)
('03 Buick Park Avenue, charcoal/cream)
Formerly:
'97 C230, smoke silver/parchment; '86 420SEL, anthracite/light grey; '84 280CE (W123), dark blue/palomino

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,

__________________
* *
-- Paul W. (The Benzadmiral)
('03 Buick Park Avenue, charcoal/cream)
Formerly:
'97 C230, smoke silver/parchment; '86 420SEL, anthracite/light grey; '84 280CE (W123), dark blue/palomino

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.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

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.)

__________________
* *
-- Paul W. (The Benzadmiral)
('03 Buick Park Avenue, charcoal/cream)
Formerly:
'97 C230, smoke silver/parchment; '86 420SEL, anthracite/light grey; '84 280CE (W123), dark blue/palomino

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

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.

__________________
* *
-- Paul W. (The Benzadmiral)
('03 Buick Park Avenue, charcoal/cream)
Formerly:
'97 C230, smoke silver/parchment; '86 420SEL, anthracite/light grey; '84 280CE (W123), dark blue/palomino

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.

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?

__________________
* *
-- Paul W. (The Benzadmiral)
('03 Buick Park Avenue, charcoal/cream)
Formerly:
'97 C230, smoke silver/parchment; '86 420SEL, anthracite/light grey; '84 280CE (W123), dark blue/palomino

Seen it for less,much less.

Could help alot.

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

__________________
08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280