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Matt, Mechanical Engineer
Category: Mercedes
Satisfied Customers: 24224
Experience:  BEng hons Mech engineering, in auto industry 22 years
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I have a 2001 Mercedes C220 CDI. Kept going into limp mode

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I have a 2001 Mercedes C220 CDI. Kept going into limp mode and discovered the primary catalytic converter was clogged up, removed and cleaned and also replaced the air filter. Have cleaned ERG valve and MAF sensor. reset all error codes.
Then started getting a check coolant level and the radiator fan is running flat out and car now permanently in limp mode.Checked coolant level and it is fine, no leaks anywhere and car is not overheating, on the advice of someone else on here I disconnected the battery and went through an ECU master reset procedure. Still getting coolant level warning and now getting ESP warning as well. i have not driven the car as yet. Any ideas as to what is going on? Only had this car for 3 weeks and I just want to sort it so that i can get rid of it ASAP. I hate the thing with a vengeance and will never buy either a diesel car or a Mercedes ever again.


OK the coolant level warning is usually a faulty level sensor in the header / expansion tank so thats usually rectified by cleaning the sensor and washing out the tank

now regarding the ESP warning then this is quite possibly the reason for the limp home mode

The quickest route to repair is to have the car plugged into a diagnostic machine which will read off the fault code stored in the ECU (providing the light is still on at this point) and indicate which sensor has failed or whether the fault is more serious.

However with ABS / ESP systems 99% of the time its a problem with one of the wheel speed sensors and I'd first check the connections at all four corners first for any signs of corrosion or chafed wiring.

The sensor is located in the wheel hub so you'll have to remove each wheel in turn to inspect them all.

Also check that the toothed wheel that the sensor points to is clean and free of any debris.

you can check each sensor's function by plugging the two output wires into an AC voltmeter and spinning the wheel quite quickly, you should get a voltage signal that increases with rev's.

Its possible that the fault is only a bad connection to one of the wheel sensors.

This may be remedied by removing each wheel in turn and unplugging each sensor and cleaning the contacts with a squirt of electrical contact cleaner. Then refitting.

If the battery has been disconnected then it is necessary to perform a zero point calibration of the steering angle sensor. To do this you need to start the car and turn the steering wheel all the way to the left and then all the way to the right 5 or 6 times

Customer: replied 2 years ago.
The car was going into limp mode long before the ESP light came on, that only came on today after disconnecting the battery.


the coolant level sensor can put you into limp home so its well worth rectifying that and try the steering wheel calibration to see if that removes the ESP fault too

Customer: replied 2 years ago.
OK cheers ***** ***** give that a go tomorrow


just get back to me on this post

Customer: replied 2 years ago.
Hi MattI tried cleaning the cooling system sensor and tank but the error still persists, I have ordered a new sensor for both tha header tank and for the washer bottle, good news is that after turning the wheel back and forth the esp error dissapeared.Had the car on diagnostics yesterday and was showing the following:Electric suction fan Open circuit
Charge pressure control Open circuit in wiring signal wire
B2/5 Maf signal voltage is low
EGR Open circuit
M55 Inlet port shutoff motor Check signal line of component M55 for discontinuity.this is the first time these errors have shown up.having performed diagnostics 3 times in the past 2 weeks i have noticed that I am getting completely different errors each time.I noticed that on starting the car the dash display and interior lights fluctuate in brightness regardless of whether on tickover or when driving. i put a voltmeter across the battery with engine off and was getting around 12.6 volts, with engine running the voltage seems to fluctuate very quickly up and down between around 12.8 and 14 volts.
I have therefore assumed that the voltage regulator on the alternator is breaking down and causing spurious voltages.
Could this upset the ECU and cause the different errors to keep showing up?

thanks for the extra information

yes a low and variable battery voltage will create all sorts of odd spurious faults

what quite likely is the battery may be on its way out as if this has a burnt out plate then this greatly lowers its capacity to absorb voltage spikes

if you were to have it load tested then this would confirm this

also check the condition of the engine earth connections and the main battery connections

all must be bright and tight to avoid issues

Customer: replied 2 years ago.
Going to drop test the battery tomorrow, all ready checked all battery and earth connections, but will double check just in case I have missed one, looking on the bright side by the time I get finished I shall have a much better idea of how all the comms systems and sensors work.Many thanks will let you know what I find tomorrow.Dean


good luck


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Customer: replied 2 years ago.
Hi MattFinally resolved the coolant warning issue and problem with car going into limp mode.
Discovered blown fuse number 54 which feeds some of the sensors that were all showing errors. replaced fuse and after a few mins it blew again, investigated further and found a short circuit in the wiring to the charge pressure sensor, rectified the problem and replaced fuse and the car is now running fine and showing no faults. many thanks for your input.regardsdean