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I was driving in stop and go traffic on the freeway, 0-5 mph for many miles. While on a slight incline my warning lights all came on at once and I had to push on the brake pedal really hard to get the car to stop. As I tried to get over to the shoulder, I noticed the acceleration was not working — I had to coast. The headlights and radio remained on the whole time. I made it to the shoulder and turned the car off for a few minutes. I turned it back on and there were no warning lights and the idle felt normal. I drove about 10 more freeway and street miles without incident. Stopped for dinner after which I drove about five miles without incident. What happened??
I was driving in stop and go traffic on the freeway, 0-5 mph for many miles. While on a slight incline my warning lights all came on at once and I had to push on the brake pedal really hard to get the car to stop. As I tried to get over to the shoulder, I noticed the acceleration was not working — I had to coast. The headlights and radio remained on the whole time. I made it to the shoulder and turned the car off for a few minutes. I turned it back on and there were no warning lights and the idle felt normal. I drove about 10 more freeway and street miles without incident. Stopped for dinner after which I drove about five miles without incident.
What happened??
An odd condition caused your engine control module to get into Limp-Mode. Restarting the car cleared the condition like nothing ever happened.
I believe this is caused by computer networking.
Many shops including dealers may replace tons of parts for zero result and no warranty. Be sure to refuse estimates done without any TESTING.
Get a complete scan report to hopefully provide clues - I think this is a stealthy unlogged condition... not too uncommon.
Last edited by CaliBenzDriver; Feb 16, 2024 at 04:09 AM.
Welcome to what could be a very long diagnosis. Intermittent faults are usually the hardest to find. Don't be fooled into changing anything at the start unless there is unequivocal proof that it's the fix.
There are too many stories here of people who've unloaded the parts canon on their cars at great cost, and yet they still have the problem, or it turned out to be something simple they overlooked at the start.and theyve spent a heap of cash on parts they didn't need.
Time, research and a scan tool will help as well as a good independent MB mechanic.
I'd suggest like CaliBenz that you most likely have an ECU or harness/wiring fault. Preparation prior to diagnosis is the key. Start with checking battery (incl terminals) and alternator to make sure everything has adequate voltage. 11.7v minimum engine off and 13.7v engine running. Then the ground wires and connections to make sure there's no corrosion and they have a good contact base.
After that, you can then start on more specific areas depending upon where your research and advice sends you. Its essentially a process of elimination. Best ot luck.
Last edited by BlackML550; Feb 16, 2024 at 07:25 AM.
I would hook up my obd scanner and see what if any faults are showing. Write them all down then erase them. Post the results here, im curious what they show.
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
As @BlackML550 said, "Time, research and a scan tool will help as well as a good independent MB mechanic."
My face is blue from saying this over and over, get a Mercedes-specific scan too!
Many recommend the LAUNCH Creader Elite 2.0 BENZ, though iCarsoft and Foxwell are also recommended. Any of them should be under $200 and less on Amazon. You will not only know exactly what codes were thrown, but sometimes simply stopping and restarting the car will not work, while using the scanner to clear the codes will. Clearing codes will not fix the root cause of any fault, BUT may get you back on the road far enough to get home or at least a safe place.
Your car is 14 years old. You need the right scanner more than a brand new car (though I recommend one for new cars, as well).
Last edited by JettaRed; Feb 16, 2024 at 09:53 AM.
As @BlackML550 said, "Time, research and a scan tool will help as well as a good independent MB mechanic."
My face is blue from saying this over and over, get a Mercedes-specific scan too!
Many recommend the LAUNCH Creader Elite 2.0 BENZ, though iCarsoft and Foxwell are also recommended. Any of them should be under $200 and less on Amazon. You will not only know exactly what codes were thrown, but sometimes simply stopping and restarting the car will not work, while using the scanner to clear the codes will. Clearing codes will not fix the root cause of any fault, BUT may get you back on the road far enough to get home or at least a safe place.
Your car is 14 years old. You need the right scanner more than a brand new car (though I recommend one for new cars, as well).
I am 4.5 years into a "6 year" Interstate battery (two prior Mercedes batteries crapped out after about barely 3 years each), so I'm hoping it's something simple like that. Also, I just had the intake manifold replaced (cc: Tim C300) and a day later the check engine light came on. It turned out there was a problem with a vacuum hose that was easily remedied. I wonder if this could be another hose/harness/wiring fault stemming from that repair. Meanwhile, I am terrified of going into limp-mode again, but at 70 mph instead of 2.
In any case, I ordered the LAUNCH scanner and will update. Thanks for all the responses.
Last edited by Aging C300; Feb 16, 2024 at 01:04 PM.
Reason: Add info
PS I have a rudimentary scanner, Motopower MP69033. This $20 scanner threw a cylinder misfire code after the intake manifold was replaced -- which turned out to be the vacuum hose issue -- but did not show the intake manifold flap malfunction code that both the dealer and my mechanic saw on their genuine scanners, which was the impetus for replacing it. So I guess Moto only shows a handful of codes, It showed no fault codes this morning when I hooked it up. I'm sure the Launch will do better.
In your 1st post you mention having to push the brake pedal hard then acceleration issues with warning lights coming on. Vacuum leak may cause all that. I know in my M272 the brake booster is connected directly to the vacuum pump.
Were you braking and then the warning lights came on?
The vacuum hose is the one on the left with white numbering all over it.
In your 1st post you mention having to push the brake pedal hard then acceleration issues with warning lights coming on. Vacuum leak may cause all that. I know in my M272 the brake booster is connected directly to the vacuum pump.
Were you braking and then the warning lights came on?
The vacuum hose is the one on the left with white numbering all over it.
I was riding the brakes on a downhill slope going like 3 feet and braking then 10 feet and braking then 2 feet and braking, etc. So the lights probably did come on while I was in the process of braking. I will look at the condition of that vacuum hose tomorrow in the light of day.
I would hook up my obd scanner and see what if any faults are showing. Write them all down then erase them. Post the results here, im curious what they show.
Launch Creader 2.0 Health Report Fault Codes:
P0606 - Component Y3/8n4 (fully integrated transmission control control unit) is faulty.
B18CC01 - The output for actuator "Fuel filler flap" has a malfunction. There is a general electrical fault.
9dd015 - The output for the mirror heater has a malfunction. There is a short circuit to positive or an open circuit.
I also checked the alternator and battery and got the following data:
Alternator ID - 3
Battery - 13.66v
Calculated Alternator Torque -5.5
Electrical Fault Alternator - NO
Engine - 690 RPM
Mechanical Fault Alternator - NO
I don't know how to check the transmission with the scanner, but I got to the part where is showed the data. Do I drive around with the scanner plugged in and print a report??
P0606 - Component Y3/8n4 (fully integrated transmission control control unit) is faulty.
B18CC01 - The output for actuator "Fuel filler flap" has a malfunction. There is a general electrical fault.
9dd015 - The output for the mirror heater has a malfunction. There is a short circuit to positive or an open circuit.
I also checked the alternator and battery and got the following data:
Alternator ID - 3
Battery - 13.66v
Calculated Alternator Torque -5.5
Electrical Fault Alternator - NO
Engine - 690 RPM
Mechanical Fault Alternator - NO
I don't know how to check the transmission with the scanner, but I got to the part where is showed the data. Do I drive around with the scanner plugged in and print a report??
PS I deleted the codes and went for a drive, using both S and C driving modes. Transmission did not seem weird at all. When I returned home I scanned again and the Health Report did not have the TCM or mirror heater fault codes. The fault code for the fuel filler cap remains. No idea if that could have put the car in limp-mode as described above.
Have you had a flat battery or had to jump start it? The codes you have a far and wide. But it looks like your battery and alternator are ok.
The fuel filler cap is probably leaking and letting in air. Try and few layers of plastic wrap around the inside of the cap and reseal it and see what happens.
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
"P0606 - Component Y3/8n4 (fully integrated transmission control control unit) is faulty" may be early warning of an intermittent or worsening tranny conductor plate failure. Usually, when the code gets thrown and you go into limp mode, turning the car off and then back on will "fix" it for a while. A conductor plate replacement will run about $2000 (my guess--it could be more) and normally must be done by the dealer. Mercedes will not sell you the part directly. However, since it was STORED and not CURRENT, it could have been triggered by a weak battery. When running, my car normally shows 14.3V, so 13.66V is actually a little low.
Did you have all electrical consumers (A/C, lights, COMAND, etc.) off when measuring the voltage?
How many miles on the car?
When was the transmission last serviced (i.e., fluid and filter change)? Your car is 14 years old and should have been serviced at least once, if not twice. Tranny service is required based on either miles or age.
"P0606 - Component Y3/8n4 (fully integrated transmission control control unit) is faulty" may be early warning of an intermittent or worsening tranny conductor plate failure. Usually, when the code gets thrown and you go into limp mode, turning the car off and then back on will "fix" it for a while. A conductor plate replacement will run about $2000 (my guess--it could be more) and normally must be done by the dealer. Mercedes will not sell you the part directly. However, since it was STORED and not CURRENT, it could have been triggered by a weak battery. When running, my car normally shows 14.3V, so 13.66V is actually a little low.
Did you have all electrical consumers (A/C, lights, COMAND, etc.) off when measuring the voltage?
How many miles on the car?
When was the transmission last serviced (i.e., fluid and filter change)? Your car is 14 years old and should have been serviced at least once, if not twice. Tranny service is required based on either miles or age.
1. I think everything was off.
2. 133k
3. Transmission fluid and filter were replaced at 80k service (March 2018).
Have you had a flat battery or had to jump start it? The codes you have a far and wide. But it looks like your battery and alternator are ok.
The fuel filler cap is probably leaking and letting in air. Try and few layers of plastic wrap around the inside of the cap and reseal it and see what happens.
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
I would say to keep an eye on things, but the tranny going limp doesn't warn you ahead of time. Power off reset often is a good temp fix. Now that you know what to expect if it happens again, try to move out of traffic before hitting the brakes.
I had the same thing happen on my 2004 SL500 while going through a construction zone in rush-hour traffic. Not fun trying to get to a safe place when all the shoulders are blocked. Shortly after that, I had my conductor plate replaced by the dealer. I think it was around $1700 at the time. But that did of course include a tranny service.
Have you used the heated mirror function since clearing the codes?
Isn't the code for the fuel filler cap having to do with it locking/unlocking the filler door? Does the door lock and unlock when using the key fob? I'm assuming it is if your getting gas.
Mines a 2010 and records show trans serviced at 40,000 miles, 80,000 miles and now its a little over 150,000 miles and Im just waiting for nicer weather to do it myself, along with replace the rusted trans pan. My Maintenance manual says it should be serviced every 40,000 miles.
Awhile back I was pulling into my parking spot in the back, i do a large half circle then back up into my spot which is on an incline. Soon as I stepped on the brakes to stop and put it in reverse it stalled, oddest thing. Hasn't happened again since. Maybe this was just an odd one time issue. few months ago my red battery light was showing on the dash, was driving me crazy trying to figure it out. hasn't happened since.
last thing, when you mention going down an incline im wondering how much gas you had in the tank, if it was very low maybe something with the fuel pressure, Im totally speculating on this one.
Have you used the heated mirror function since clearing the codes?
Isn't the code for the fuel filler cap having to do with it locking/unlocking the filler door? Does the door lock and unlock when using the key fob? I'm assuming it is if your getting gas.
No. The fuel tank is pressurised so the evaporative system draws fumes from the tank through the charcoal cannister and then to the inlet manifold to burn the fumes and reduce pollution. If the gas cap is not sealing properly, the system loses vaccum and that triggers a code. You could drive around without the gas cap door and the car wouldn't know.
Have you used the heated mirror function since clearing the codes?
Isn't the code for the fuel filler cap having to do with it locking/unlocking the filler door? Does the door lock and unlock when using the key fob? I'm assuming it is if your getting gas.
Mines a 2010 and records show trans serviced at 40,000 miles, 80,000 miles and now its a little over 150,000 miles and Im just waiting for nicer weather to do it myself, along with replace the rusted trans pan. My Maintenance manual says it should be serviced every 40,000 miles.
Awhile back I was pulling into my parking spot in the back, i do a large half circle then back up into my spot which is on an incline. Soon as I stepped on the brakes to stop and put it in reverse it stalled, oddest thing. Hasn't happened again since. Maybe this was just an odd one time issue. few months ago my red battery light was showing on the dash, was driving me crazy trying to figure it out. hasn't happened since.
last thing, when you mention going down an incline im wondering how much gas you had in the tank, if it was very low maybe something with the fuel pressure, Im totally speculating on this one.
I didn’t even know I had a heated mirror function!
I don’t have a lever or button or anything to open the fuel filler door — I just push and it pops open if the car’s unlocked. So kinda confused about that fault message.
I feel like the transmission service should’ve been done at 120k! My mechanic blew it. Maybe I’ll have my new mechanic do it and replace the battery while I’m at it.
Gas was about 3/8 full for the incident.
I will keep an eye on things and pray this was just a fluke like your battery light.
Thanks.
Last edited by Aging C300; Feb 19, 2024 at 05:24 PM.
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
I "think" the fuel flap door may have something to do with the locking mechanism, but that is just a guess. If the fuel cap was left off, I think you would get a purge valve error, but definitely a CEL.
I found out my drivers mirror is heated when I was fiddling around with my Mercedes scanner, came across an option to test it, turn it on and off using the scanner. I think it works automatically when the heat is turned on, or maybe the defrost. I was thinking maybe the code didnt come back because the heated mirror function hasnt been used since clearing the codes, or it was a random code and fixed itself.
I think the fuel filler flap actuator is mounted to the back of the filler door assembly. Its what lock/unlock the door from being opened. I know my fuel door wont open unless the car is unlocked. looking at the parts diagram it shows a harness at the filler door (900). And part 440 is the emergency pull located in the trunk if theres an electrical problem so you can get the door opened.
Try your door, see if its always opened.
photo os a used filler door on eBay, can see the electrical connection.
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