When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
2002 ML-500 BAS/ESP limp - P2600 transmission code not clearing
Hi, I'm new to this forum, so I apologize in advance for any errors in adhering to posting protocols. I acquired a 2002 ML-500 in January. The truck has 123,500 miles and was garage stored by the previous owner for the past 14-16 months. There were many many issues with the vehicle when I first received it, so I started researching and eliminating one at a time. Here are some of the major maintenance items that I performed:
- replaced air filter
- cleaned MAF but then eventually replaced it (aftermarket). There was no difference noticed with this change.
- replaced all 16 spark plugs (previous plugs were not too bad but wanted a clean maintenance baseline)
- replaced crank shaft position sensor
- replaced the transmission valve cover conductor plate (as vehicle was stuck in limp mode) - started shifting again after this fix. Also performed the relearn reset.
- replaced acceleration pedal sensor (with calibration/relearning)
- replaced fuel filter (previous filter was causing pressure fluctuations. Pressure stabilized at around 58 psi after filter change)
- replace battery with new BOSCH unit (previous battery was not holding charge properly)
- replaced brake lamp switch (based on numerous posting that showed this was a common issue)
- replaced lateral position sensor (no change in vehicle operation so returned part and replaced with old one)
- replaced the Yaw sensor (noticed improved stability - less occurrence of limp mode at various speeds after disconnecting the old one, so decided to replace it)
- reset all fault codes (carsoft i980 scanner that reads/resets MB specific codes)
The vehicle is no longer throwing a check engine light. No more misfire codes and better idling. However, I'm still stuck with one major problem that essentially makes the vehicle unusable. It performs fine up to around 40 mph, shifting normal. However, when I try to accelerate beyond, acceleration is extremely poor and the ML goes limp, loss of power and the BAS/ESP light turns on. When this occurs, I pull over, switch off and on the vehicle and the vehicle seems to operate normal again until I try the same steps (100% repeatable). I've checked numerous postings across the internet and am still unable to pinpoint the issue with this truck. I ran another diagnostic today and noticed that the transmission module is showing a P2600 code (the voltage supply of circuit 87 has undervoltage). The code reappears immediately even if cleared.
Would appreciate any advise to further troubleshoot this issue. I've also noticed that my hair has turned white since I purchased this vehicle. Is that normal?
I believe the code reader you are using is just that, a code reader, which will only read engine codes. You need a scanner type which will read codes in every module and in this case the ETC Module.
Whenever there is a code stored in the ECM which relates to the Trans., there is a corresponding code stored in the ETC (Trans.) Cont. Module. Those codes must be read and dealt with.
So, even if you found and corrected the problem, both the codes in the ECM and ETC modules must be cleared individually. If not, the codes will recur.
ECM codes were cleared after fixing other issues. There are no pending ECM codes. ETC code was cleared but keeps showing P2600.
I checked fuse 22 and both contacts show 12v. Shift indicator is fine and showing correctly on the instrument cluster.
I went through this before but I had the triangle flashing on the dash when losing power at 50ish mph, then the BAS/ESP lighting up. Similar to this, although not braking but refusing to accelerate: https://mercedesforum.com/forum/gene...locking-24171/
Car gets up to speed and one of the sensors reads faulty and the car thinks it is spinning off the road or has gotten into a wreck and shuts down.
It ended up only being a wheel speed sensor starting to go. Other forum threads will corroborate this if you search around. It's pathetic that the whole car shuts down over a wheel speed aka abs sensor, but it does. It wouldn't officially throw a code unless I accelerated quickly (floored it) from 0 mph after the car was warmed up from driving, at which point the BAS/ESP and ABS lights and Check Engine would light up solid and the car would drive normally with the code (P0500) then being readable.
Unplug one of the wheel speed sensors to disable the abs system and then attempt to recreate the problem - you shouldn't be able to. I unplugged one of mine to disable the abs/esp system and be able to drive normally until the new part arrived.
Does your reader give wheel speeds if connected and driving? Maybe try that to determine which sensor. They aren't the best design, are easily compromised and do go bad. You might be able to just clean them. Since you're a proactive replacer, you might as well just replace all 4 - the chinese sensors are inexpensive and good quality but make sure you get the right one using the part number from the actual sensor wire. I believe the '04s are different from some of the pre-'03 W163s.
When I had this problem I remember faulty ABS pump being a recurrent possibility when searching for solutions. Also, steering angle sensor as mentioned in the above link.
Other advice I remember was to reset by turning the wheel lock to lock a dozen or so times.
The next step would be to check cir. 87 with a DVOM at the ETC Cont. Module at conn. #1, wires 1-30 while the connectors are in place.
I checked the voltage on pin 30 and 29 and it read 12v. I also checked 30 + 1 but there was no reading. I wasn't able to perform the test with the connector in place as there's no place to insert the probes while connected.
I also performed the following:
I allowed the vehicle to warm up good and then rechecked the transmission oil. It was a bit low and I ended up adding about 1/2 qt. I also disconnected the plug from the transmission wiring connector and cleaned it with contact cleaner and then used compress air to blow out any debris.I checked the transfer case oil and topped it off (about 1/3 qt). Finally, I reset the transmission adaptive learning. Took the vehicle for a drive (taking it really easy). I allowed a gradual/smooth shifting (without heavy acceleration). After about 20 minutes I started increasing the speed and was able to get it up to around 65mph (for the first time) without the BAS/ESP light tripping. I took it back out for a second run a couple hours later. It seemed to be shifting good (not perfect, but much better that before). I stopped for a red light and another driver pulled up beside me and said my brake light are on all the time. This is odd because I changed the brake lamp switch a few weeks ago (guess I will need to get another). My CEL also came on about 5 mins before I got home. It's showing a P0101 code (Mass air flow). Probably the aftermarket MAF failing. So I plan to replace both the brake lamp switch and the MAF with an OEM part. The ETC is still showing a P2600 code, but the trans seems to be working much better after correcting the fluid level. I will post an update once I make the changes next weekend.
The next step would be to check cir. 87 with a DVOM at the ETC Cont. Module at conn. #1, wires 1-30 while the connectors are in place.
Originally Posted by Aar Sto
I went through this before but I had the triangle flashing on the dash when losing power at 50ish mph, then the BAS/ESP lighting up. Similar to this, although not braking but refusing to accelerate: https://mercedesforum.com/forum/gene...locking-24171/
Car gets up to speed and one of the sensors reads faulty and the car thinks it is spinning off the road or has gotten into a wreck and shuts down.
It ended up only being a wheel speed sensor starting to go. Other forum threads will corroborate this if you search around. It's pathetic that the whole car shuts down over a wheel speed aka abs sensor, but it does. It wouldn't officially throw a code unless I accelerated quickly (floored it) from 0 mph after the car was warmed up from driving, at which point the BAS/ESP and ABS lights and Check Engine would light up solid and the car would drive normally with the code (P0500) then being readable.
Unplug one of the wheel speed sensors to disable the abs system and then attempt to recreate the problem - you shouldn't be able to. I unplugged one of mine to disable the abs/esp system and be able to drive normally until the new part arrived.
Does your reader give wheel speeds if connected and driving? Maybe try that to determine which sensor. They aren't the best design, are easily compromised and do go bad. You might be able to just clean them. Since you're a proactive replacer, you might as well just replace all 4 - the chinese sensors are inexpensive and good quality but make sure you get the right one using the part number from the actual sensor wire. I believe the '04s are different from some of the pre-'03 W163s.
When I had this problem I remember faulty ABS pump being a recurrent possibility when searching for solutions. Also, steering angle sensor as mentioned in the above link.
Other advice I remember was to reset by turning the wheel lock to lock a dozen or so times.
My iCarsoft i980 scanner is able to read the ABS codes. I checked and found code P102400. The scanner states that The fault code is not found in the database. I wasn't able to find much information on this code. I plan to clear the code and will check again after driving for a bit. I may take your advice and replace all 4 wheel sensors since it's an inexpensive fix (although I would expect to see some fault codes if the sensors were failing).
If your brake lights are always on it definitely could cause TPS and MAF problems. This car talks to itself too much. I think the order you need to look at in resolving your problems should start with the ABS system. I recall having maf problems after doing the 2 minute key-in reset because of the failing wheel speed sensor. The BAS/ESP is a good indicator that the car is spazzing out from lack of alignment, from bad abs sensor, from bad steering angle, other sensors. Obviously, you've tried the clock to clock to reset the steering angle alignment?
I replaced it a few months ago when the car was stuck in limp mode after seeing numerous postings that a malfunctioning brake lamp switch could cause this issue. It seemed like an inexpensive and easy fix at the time. My issue was clearly speed sensor related and was only fixed after replacing the conductor plate. I purchased the switch on ebay from a big parts seller that I've used before. The part is black... which I realize now is likely incorrect but their fitment software indicated that it was correct for my vehicle. I ordered a new one (blue) which should arrive later this week.
In the mean time access your BLS and manually push down the brake pedal and with the other hand pull out the actuator pin as far as possible. Then pull up on the brake pedal and release. Turn key on and see if you brake lights are still on.
If the brake lights go out, then clear all codes in every module.
As I mentioned in my initial post, I purchased the car in in January from California and had it shipped to New Jersey. The car was garage stored for over a year and the owner was just about to donate it to free up space in his garage. When I received the car, it clearly had some issues. Transmission was stuck in 2nd gear which got resolved after replacing the conductor-plate. Still, there were issues with acceleration. For a big engine there was hardly any power and the car felt like it was choking. I changed the acceleration pedal sensor and that fixed another DTC I was reading. Still no power. Vehicle was hesitating on acceleration and would go into limp mode. I checked the fuel rail pressure and it was fluctuating from 0-30 psi rapidly. I changed the fuel filter and pressure stabilized at around 58psi. I also did a full tuneup on the vehicle. There was some improvement but still no big power and acceleration remained poor. I finally decided to replace all breather hoses and to fix the leak on the breather valve covers last weekend. When I took off the air tube going to the intake manifold, I found the following:
Needless to say, after removing the blockage and finishing the breather valve and hose job, the vehicle came alive. The acceleration and overall power is through the roof!! I'm still not sure what is causing the P2600 code on the ETC but for now I'm enjoying the ML-500. Thanks to Maj. Dundee & Aar Sto for taking the time to assist with my troubleshooting. Much appreciated!!
06-03-2018, 01:42 PM
2002 ML-500 BAS/ESP limp - P2600 transmission code not clearing
