kingjoe206

Hi, I hope this issue hasn't been addressed already. I've seen plenty of threads with similar issues, but mine seems to be different. My girlfriend's Dad has a 2001 c240 w203 with 167k miles which has been nothing but problems since he bought it.

The car looks like almost everything was taken apart at one time and not put back together properly. It's missing screws, heater control knobs are missing/ broken, various pieces under the hood are also missing. Nothing that should affect anything mechanical or electrical, but shows whoever worked on it was probably not the most competent person ever.

I don't know exactly how this started, but currently to the car won't start, or even crank. Fuel pumps turns on fine, it starts when I put 12 volts directly to the starter, but it drives really slow. I don't even need to press brake to shift out of park, and the dash doesn't recognize I'm shifting gears. When I first get in and try to start I hear a loud clicking noise coming from the center of the dash, almost behind the stereo or the center vents. Also there is a high pitched noise coming from the maf or throttle body that will eventually sound like a fan cutting out. The brake lights work, the car idles nicely, alternator works, it was missing auxiliary ground to body, but I attached one. The key fob lights up when I press the buttons, but won't lock/unlock the doors.

I was only able to hook it up to a generic diagnostic tool, I don't remember the exact codes, except P0600 (obviously generic), but they were all related to no communication with tcm or pcm. I can't see any water damage to the ECU. But the windshield wipers won't turn on so I can't even remove the ECU.

I checked all relevant fuses (except wiper fuses, just realized that problem last night when it was already dark and I was done working on it). None of the starting system fuses are bad, the battery is new and up to specs, and as far as I know there is no neutral safety switch on the w203's.

Sorry for the long post just wanted to be as specific as possible. Hope you guys can help. And thanks for all the great info on these forums, I'm a new member but the info on these forums has saved me a few times.

Plutoe

kingjoe206

Yes. I said that in my first post.

Plutoe

I deleted the redundancy in post 2---However my further comments are related to the starting issue!

In the front SAM you have the 15 and 15R relays--I would check them!

Secondly, although you did not advise whether you could move the key in the ignition control module, I am assuming you can't--if that is the case then you may have an issue with the Drive Authorization System(key, module, steering lock module)one of the components is faulty!

How do I test systems like yours, I use DAS Xentry diagnostic tool to quickly determine the faults------what do you do without a similar tool--IHGTFFI! except find help with with someone with factory or equal diagnostics.

kingjoe206

Sorry if I wasn't clear, but the key does turn. It does start when I manually engage the starter.

I know there is s transmission control module under the passenger side carpet. I was wondering if it's bad would that prevent the car from starting? And why I can put it in drive without even touching the break pedal? And what the clicking in the dash might be?

I'm leaning toward bad ecu or tcu, but don't want to start buying expensive parts unless they are necessary.

Kazi04

First thing I would do is check your battery voltages when the car is running and when the car is not. That will tell you if your battery has enough juice to turn the starter along with everything else it does when the key is turned. A have heard of a bad battery causing all sorts of electrical issues.

kingjoe206

Ok thank you I will try later today.

kingjoe206

Ok, tested the voltage. I got 12.45 when the car is off and 14.07 when running. I'm not sure with Mercedes but sounds like that should be enough. What is the best way to test the relay?

Trinidad Local

Please replace relays m p and r. M and P can be replaced with any normal relay. R is a big pronged relay.

Trinidad Local

The tcu is not getting the engine signal, it is running in failsafe mode.

kingjoe206

Will replacing the relays help this issue? If not is there something else I can do? Thank you for the response btw

C240Keese

Im pretty sure you have a bad shifter since the car doesn't show you shifting out of park. You not having to hit brake is another symptom of the same part. Mines used to shift out of park with brake held but once I past reverse it wouldn't go back up past neutral as if I let go of brake. and also didn't show whether I was in P,R,N,D

TCU/TCM has nothing to do with you holding the brake and shifting out of park. There is a cable that goes from the shifter to the ignition switch that is what's responsible for that. Because if the car knows your not in park you can't take the key out.
The TCU is responsible for the learned shift points and driving mode like C,S,or W

I have also heard of the TCM causing no start issues but im not sure. Get yourself a multimeter with the continuity test. also check voltage of the wires going to starter then back track were the voltage stops. It takes time but you'll have you answer for sure.

Clicking in the dash is the stepper motor there's a big thread on that already.

You say you attached a ground wire is that from the battery to the chassis, if so did you attach a thick enough one. I had a skinny one on mines that i bought it gave me random no crank symptoms. Ended up having to get a thicker one.

And the slow acceleration might want to check your MAF and throttle body if ones dirty they both are both pretty easy to remove and clean but only use MAF cleaner on the MAF. I remove my throttle and clean it with dish detergent then let it dry and put it back on. I now have the V8 throttle and MAF on mines. It gets better gas for sure. I avg 24 mpg just driving regular cruising I get 26.