1997 E320 transmission control module - PeachParts Mercedes-Benz Forum

justme300e · #1 01-10-2014, 01:00 PM

I purchased a 1997 e320 recently with the transmission stuck in limp mode.1st gear and reverse only.So I changed the conductor plate on top of the valve body and the associated plug.Installed a new filter and new oil.I purchased the measuring tool to accurately measure the fluid level.Okay.So I go for a test drive and it up shifted one time and went back to limp mode.there are no codes with my autotap 3.1 scan tool,but on the driver information center it reads "Lamp Defective" and when that came back on is when the transmission went into limp mode.So my question is should I change the transmission control module next,and does that unit have to be programmed or is it just a straight swap.I noticed that the right turn signal doesnt work,so I changed the bulb.It Still dont work.So the defective lamp isn't that. I was also thinking ECM ...What do you guys think? My alldatadiy service manual sucks so I got a refund.I'm also looking for factory service manual for this vehicle,any reccommendations? Thanks much!

pawoSD · #2 01-10-2014, 01:36 PM

Once the trans has gone into limp mode, the only way to take it out of limp mode is a code reset/clear by the dealer or a mechanic with the proper factory computer, even if you replaced the part causing the issue. It will then drive normally. So you may have fixed the problem, but until the codes are cleared it will remain in limp mode. No way around it.

Gilly · #3 01-10-2014, 01:40 PM

Well that's a lot of questions.
The trans control module I believe is plug and play. I would get a scanner that can read the etc codes before trying much else. One fairly common problem on the early 722.6 is the range recognition sensor in the shifter, on this one it is available seperately, so that's good, but without a code you are just rolling the dice. If you suspect or can confirm possibly a drink being spilled on the console (or a bonehead detailer squirting cleaner near the shift gate for example) it is a good bet it is the range sensor though. Only a good bet if you think this has happened. Note proximity of cupholder in center console to shifter, doesn't take much to get a splash.
The lamp defective monitor, it would be good to track that down, everything outside is monitored, common spots to overlook are the amber side marker lamps on the sides of the front bumper, the inner oval driving lights (sort of like daytime running lights, inboard of the headlights, there are small halogen bulbs that are supposed to come on and often new owners don't realize they are out), also licence plate lights and the center stop light. I would try to track down why the signal is inop, you don't say which bulb you replaced, but whichever side you replaced (front/rear) check the other one, usually they fail to blink only because of a blown bulb. If not it is a control module probably.
I don't know what you mean by "you were thinking ECM", this is the engine control module, I would try to keep your mind off the engine control module if I were you, LOL, you don't want to go there ($$$$)

Gilly · #4 01-10-2014, 01:44 PM

Oh on the manual, MB never printed a concise manual for this car, by this time everything was going digital. You can get a subscription (last I knew) through Mercedes online where you can access all the info you would need, similar to what the dealer has available. The last I knew the site was something like startekinfo.com?

Found site:
http://www.startekinfo.com/StarTek/

97 SL320 · #5 01-10-2014, 07:18 PM

I have similar symptoms on my 97 E320 parts car. ( Limp mode is 2nd and reverse not first. ) Car was built June 96

The drivers info display has some sort of message ( probably bulb out but it has been a while since I ran the car ), high beam indicator stays on and driving lights turn on. The speedo does work but I think it gets a signal from the ABS sensor on the right front wheel. One time everything returned to normal and the trans shifted fine.

I don't recall if any codes were tripped in the trans or engine computer, I'll check next time my other computer is turned on.

My guess is that some sort of CAN connected module is failing and sending the wrong message. There is something called " Bit Rot " where a PROM / EPROM / EEPROM will start to loose internal electrical charges. This results in loss of memory and all sorts of odd behavior. I wonder if that is what is happening here.

The E320 does have a body computer of sorts, I'd like to see if there is some sort on interaction there.

I'm really like to sniff CAN traffic during the issue to see what is happening.

We need, wiring diagrams for the trans and other related systems.

justme300e · #6 01-10-2014, 08:05 PM

Thanks guys. ..anyone know of a scanner that I can purchase?

duxthe1 · #7 01-10-2014, 08:17 PM

When liquids of all sorts get spilled in the Electronic Selector Module, its common for the connector to start to corrode and the reverse light contacts short out. This causes all sorts of havoc with the trans control. As mentioned previously, the module was offered separately but even new from the dealer they were very hit and miss re: getting a good one. So much so that our shop will no longer replace the ESM. The only guaranteed repair is a new complete shifter, though even a couple of new shifters have had to be warranteed. If you find your connector corroded badly enough, it will need replaced as well. Its a PITA as the contacts are small and grouped in a bunch in the connector.

justme300e · #8 01-10-2014, 08:36 PM

Thanks guys. ..the independent in San Ramon wants 2 hrs labor@$130 an hour to hook up a scan tool and read the codes. I'd rather throw parts at it or buy my own scanner. Can anyone recommend a scanner that will read 1997 e320 transmission control module codes? And clear them

raymond~ · #9 01-10-2014, 08:43 PM

as far as I know, there aren't any code readers which can scan and delete codes
below the $200 mark. you're approaching SDS clones from Asia now, with
repurposed MB gear running upwards of $500.

justme300e · #10 01-10-2014, 08:48 PM

Are they reliable? Will it do what I need?

Gilly · #11 01-10-2014, 09:20 PM

Quote:

Originally Posted by duxthe1

When liquids of all sorts get spilled in the Electronic Selector Module, its common for the connector to start to corrode and the reverse light contacts short out. This causes all sorts of havoc with the trans control. As mentioned previously, the module was offered separately but even new from the dealer they were very hit and miss re: getting a good one. So much so that our shop will no longer replace the ESM. The only guaranteed repair is a new complete shifter, though even a couple of new shifters have had to be warranteed. If you find your connector corroded badly enough, it will need replaced as well. Its a PITA as the contacts are small and grouped in a bunch in the connector.

I hate to be overly picky about terms, but the early 722.6 (before 2000 model year I believe) shifters are not ESMs, they are mechanical except for the range recognition switch, I used to replace them all the time and worked out fine.
In 2000 model year then they were called ESM (electronic shift module), had almost no replaceable parts, just a few little sundries like clips or a screw.
If the shifter is not broken or worn out it would be the best idea to get the range recognition switch.

MAVA · #12 01-11-2014, 12:26 AM

Here is one way to get a cheap programmer. It is fifty bucks.

99 S320 Transmission Rebuild - Mercedes-Benz Forum

Martin