May I ask how old is the battery and has it been tested extensively?
When the electronics/lights go kaflooey, the battery is the culprit

The SLK wants a great battery, not a good battery

 

I would start by inspecting the area around the pilot bushing and the transmission controller - the controller's in the passenger footwell under the carpet, styrofoam, and equipment bridge. Check for any signs of wicking transmission fluid, especially look for transmission fluid in the yellow foam rubber insulation in the area where the wire comes up through the floorboard.

 

From what I have gathered and experienced so far, a lot can revolve around those brake (speed) sensors. I had all the symptoms with the lights but not the top. I can see how it would affect the top as well seeing how the top up and down function is only allowed based on vehicle speed (less than 3mph on mine). My issue was a bad right front brake (speed) sensor. You said you replaced both rear, yours not have front as well? Technician stated to me that this is the most common cause of these problems and the trick is finding out which sensor is bad. If you have only two sensors on rear and you replaced both, could be defective sensor. These things sure do go bad a lot (I think its a racket to jack peeps wallets, $400-$500 to replace one and its so easy). I would check those sensors
b4 I went any further. I really think these sensors are manufactured to fail after a short period:|

 

Thanks for the good comments and suggestions. We had the battery checked and it was down a little on CCA's even though it was only a couple years old. New battery installed under warranty and problem is still there. Also checked for wicking of transmission fluid around wires in passenger floor area...everything looked clean and good. Have ordered the two front wheel speed sensors, although not sure what these sensors control other than the ABS, of course. With regard to the rear wheel speed sensors that were previously replaced, only the left one had what appeared to be some damage on the end of it. By the way, even though the car is 18 years old, it has only approximately 90K miles on the odometer.

 

Those sensors (magnetic) only do one thing, they tell the computer what speed the wheel is turning. This affects everything associated with the brakes, ABS (anti-lock brake system), ESP (electronic stability program), ETC (electronic traction control), brake hold feature (BAS), even CEL light can come on. All these systems utilize the brake system to function and need individual wheel speed input from these sensors. I am sure the wheel speed monitoring also affects things like top up and down, maybe tranny as well. Please post results after you replace the front sensors, I am almost certain it will fix your problem. Be interesting to know as this is proving to be a common problem, hope it works for you:smile:

 

The front wheel speed sensors came in today and we installed them late this afternoon. The result: No change except the "CHECK ENGINE" light was not on during the very short test drive. Speedometer/odometer still inoperative, automatic transmission does not shift, top does not work (red control knob flashes), and these lights are still on: “BRAKE”, “ABS”, “BAS-ASR”, and the worn brake pad icon.

A few days ago I found this at justanswer.com during a google search using "P0500" and "P1747" and "transmission":

Have a 99 SLK230 with a P0500 and P1747 code. all warning light

The "expert's" answer was that this could be a problem with either the transmission shifter mechanism/electronics or the transmission speed sensor on the conductor plate (internal to the transmission). So...considering a possible shifter problem, we decided to test drive the car in the "W" (winter) mode after flipping between the "S" (summer) and "W" setting several times. During this test drive, all the warning lights went out, but the speedometer/odometer still did not work and the transmission did not shift and the top still did not work. We now tried the car with the transmission in the manual mode, starting in 1st gear. Although the top still did not work, all warning lights remained off, and the transmission shifted. However, a new problem showed up: there was a noise from the rear (right side?) and the ASR symbol light (triangle with exclamation point in center) flashed. This happened several times during the short drive of about 100 yards. Checking the brakes calipers, the right rear one was too hot to touch. The left one was not even warm. (The car continued to make the noise with the flashing ASR light with the transmission in the automatic mode.) Now, I'm wondering about the ABS electronic module attached to the ABS hydraulic unit. Are these known to be problem?

 

Man, all these speed sensors (tranny got one too:|) Something causing right rear caliper to brake, all sensors replaced, I would have to assume module next as well. With all these issues (could have more than one problem) I would have to get codes read either from technician or just buy you a Mercedes specific code reader (iCarsoft 980 ii). At least you can get pointed in the right direction and know for sure instead of part swapping (can be more costly)

 

From personal experience: clear the codes wth a code reader. Then pull the negative terminal on the battery for 10 minutes or so. Afterwards take it for a test drive and see where things are at. Don't forget to turn the steering wheel left to right several times, lock to lock.

Correcting the problem without resetting the system is often insufficient.

tn

 

3rd UPDATE: We installed a salvage yard shifter assembly and still have the lights on the dash (except "CHECK ENGINE" light which went away after the front wheel speed sensors were installed), car still lurches when put in drive or reverse with foot on brake pedal, and top still doesn't work. I inspected the electronics under the floor panel on the passenger side of the car (my brother had looked at this earlier and noted no apparent problems). However, in my opinion, something is going on there...there's a redish stain aroung the cable feed-thru in the floor and the cables leading to the the connector on the left side of the transmission control module (TCM) are oily. Also, when this connector is disconnected, there appears to be a slight oil film on it where it attaches to the multiple pins of the TCM. By the way, over a year ago, we had installed a new connector for the cables entering the right side of the transmission. This was because of small transmission fluid leak, which we understood was a common problem with the o-rings on these connectors. Since that installation, my brother has not seen any external leaks at that connector (or anywhere on the transmission). Here's one other thing that I should mention. My brother had found on-line a "TCU reset procedure" apparently for a 2006 SLK55 (his is a '98 230SLK) that involved turning the key to the on prosition, pressing the gas pedal down for 5 seconds. So we tried this. After going thru the procedure, when the car was started, the lights indicating the problems we are having with the car went out (as they should with the normal operation of the car)...great! However this was very short lived...they quickly came back on (within a second or two). Again, any thoughts are appreciated. By the way, as he has thought from the beginning, my brother thinks we need to replace the transmission's conductor plate and it's connecter.

 

Sounds like you have found the problem. I think your bro is right, that would be my next step (fixing the leak and cleaning the connectors)

 

I've seen vague suggestions that you can open a fluid-fouled TCU and clean it up, but I've never actually done it myself. It might be worth a try.

Try cleaning the connectors and wiring thoroughly too before you reassemble.

 

4TH UPDATE: Removed TCM and cleaned terminals with contact cleaner. Only the left connector seemed to have any oil (very, very light) on the connector (and it did not appear to be red). Used contact cleaner on all contacts on the TCM; also sprayed cleaner in both connectors. Also removed circuit board from the TCM and inspected...no apparent problem and no oil on the board. Installed the TCM and cranked the car. The lights are still on and, this time, the "Check Engine" light came back on (had been off since the front wheel speed sensors were replaced). Uncertain of what to do next. Any recommendations?

 

Did you clear all the codes with reader yet or do you have one?

 

What is the Month and Year of manufacture of your car (see your B-pillar plate)?

See Thomas Nelson's post too.

I think you've reached to the point where you really need some good diagnostic tools, e.g. CAN diagnosis, to avoid any further guesswork. You earlier mentioned a CAN problem... and you also mentioned red stains around the wiring loom... those are smoking ****.

In the absence of better diagnostic tools - I would first inspect the CAN wiring, then replace the transmission controller, then the CP.

 

I agree, check codes first if possible. Maybe TCM bad now due to possible shorting from oil? Could be the case if you saw wire color stains from overheating.

 

QUICK RESPONSE: I'm sorry for the delay in responding to questions. The car was built in December of '97. We've cleared the codes a couple of times but they came back after just a few seconds after starting the engine.

 

FIFTH UPDATE: We went ahead and replaced the brake light switch, not expecting much and that was the case...no change. We also replaced the bushing on the automatic shift lever. Also, we reinstalled the original shifter mechanism after removing the one from the salvage yard that we had tried earlier. Of course, the bushing had no effect on the problem we are trying to solve (the original bushing was completely missing...I suppose it just broke and dropped out). By the way, on the subject of replacing the brake light switch, this was no easy job. Two panels under the dash had to be removed (one involving the hood release and diagnostic connector) with the largest one involving dealing with the very fragile plastic connectors and screw retainers. I will say that the plastic used by Mercedes is of the poorest quality I ever seen in an automobile. The plastic pieces can simply fall apart unless they are treated very carefully. When I bought the car several years back (reminder: my brother is now the owner), the biggest job at the time was tearing the dash and console apart to refinish the peeling red paint, which I understand is a very common problem with these cars...bad, bad, bad quality from a manufacturer that seems to take pride in its quality!

 

PROBLEM FOUND/REPAIRED: After replacing all four wheel sensors (new), the transmission shifter (from salvage yard), and the brake light switch (new) over a period of about 5 months, as well as trailering the car to two independent shops (one who worked only on European cars, especially, MB's and BMW's), we decided to go ahead and replace the transmission conductor plate (and electrical connector). We did this in my brother's garage after watching several internet videos, realizing that after the replacement we'd have to carry the car to a Mercedes dealer to "reset" everything. So, after the conductor plate replacement with the transmission filled with new fluid to the correct level, we loaded up the car and headed to Mercedes of Huntsville (AL). The tech there took care of that but also found the real reason for the problem: the K40 relay board. Earlier, before we did the conductor plate job, we'd removed this board from the car and examined it. Unlike some internet pictures of this board when it had failed, we could find no evidence of anything bad on it (e.g, burned/bad solder joints). Not only did the Mercedes tech find this problem and replace it with a new board, he also told us that the two new front speed sensors (after-market) that we had installed months earlier were the wrong ones and would not allow the ASR to function. We drove the car home with the ASR switched off. He suggested we reinstall the original sensors, which we did and now the car seems to be fully functional (i.e., all warning lights off, transmission shifting normally, and the top working as before*). So...much thanks to Mercedes of Huntsville for finally solving the 6=month old problem! And thanks to all who offered us advice on this very troubling problem.

* prior to this problem, we had, and still have, erratic top operation...sometimes when lowering the top, the deck lid opens and then the top does not release and lower, although the hydraulic pump continues to run.

 

I am wonder weather the problem was Really the k40 as you cleaned the terminal in the pilot bearing at the same time as you replaced the k40 .... the pilot bearing leaking onto the terminal at the tranny connector could have caused the tranny issues.