slammer111

My car is starting to give me weird electrical problems.

Sometimes when I start my car, I get a "Light Sensor" error in my cluster display. This happens maybe once a week, and always during a cold start in the morning. Sometimes in addition (during those instances with the Light Sensor error) I will also get one or both of a) ESP error, and b) SRS error, also in the cluster. So I will get 1, 2, or 3 malfunctions, and Light Sensor is ALWAYS in the list whenever I get errors.

I can get the error(s) to go away by turning off the car and restarting a few times. In every instance, the CEL does NOT come on.

One time I did NOT do this, and decided to ignore the the Light Sensor error. As soon as I put the car into D, the car SLAMMED into gear (ie HARD lurch forward), triggering the ESP + SRS errors!

Not sure if this is related, but last week the CEL came on while I was flying down the highway. My mechanic diagnosed it as a P0128 Low Temperature problem and reset the CEL for me. I noticed my car runs around 70-80C now instead of 80-90C normally, but it's also winter here in Canada with temps around 0C. So I've been monitoring the CEL, and it's never come back.

Any idea where to start looking? Dealer wants $200CAD before they'll even pop the hood. I'm hoping it's just something stupid like a loose harness somewhere. Thanks in advance.

Glyn M Ruck

Well - you need a new thermostat for your P0128 - thats a definite.

The others will be less easy to diagnose. Something was triggering limp. The light sensor should have zero to do with limp & might be getting genuinely tired. Could equally be a bad connection in the overhead console.

It could be a sign of lazy battery or charge circuit/alternator.

Has your car ever had cam sensors leak oil into the engine harness?

Has your electrohydraulic bush on the transmission ever leaked oil into the TCU harness?

pcy

^ +1.
Glen pretty much covered everything I can think of.

1st lite

I had the "Light Sensor" error show up in my display a few years back. As Glyn mentioned turned out to be the battery on its way out. Would mainly get the error message once in a while when starting my car in the morning. The error would go away after driving to work.
After the battery was replaced, the "light sensor" message never showed up again.

Funny you should mention a P0128 code. I have noticed that my temperature has not risen above 80C. It hasn't thrown the P0128 code yet, but I suspected my thermostat was starting to fail.
Looks like there's going to be some MB owners in Vancouver doing some DIY projects this month. Good Luck.

e1000

slammer111

Thanks Glyn + all the others who chimed in.

I had my battery replaced maybe 3 years ago at the dealer.

Yes I had the cam sensor leak, but it was a small weep when discovered by the dealer (I'm guessing around 10mL), not litres as some of you experienced. Fixed under recall.

Yes I had the TCU leak as well, but the dealer found and fixed that one in maybe 2006 when I brought it into service once. Also fixed under recall.

Now that I think about it, considering it always happens in the morning or after I don't drive it for a few days, it might be the battery. I'll check the voltage before driving from now on.

As for the P0128 code, a quick Google search shows maybe 5 possible problems/causes associated with it. How do you know it's the coolant temp sensor, and not, say, a low coolant level, which is also listed as a possible cause? Or is this common for the W203? It hasn't shown up since at all.

Glyn M Ruck

P0128 is common on W203 - Benz thermostats are designed to fail open. For sure it's the thermostat.

alanchan

sorry to hear that ED,

I had mine CL230 park outside for the last 3 months and it fire up fine, no error.

hope you get it fix soon so we can meet.....

cheers

slammer111

Glyn, I found this post.

https://mbworld.org/forums/c-class-w...ml#post4283901

A quick search of RMEuropean shows only a 271-203-05-75 (90C) sensor. Can anyone verify if a 87C version still exists, or if both 00-15 and 03-75 have been superseded by this one?