enap66

My 2004 C240 started running strange. Wouldn't start properly, sometimes the engine would just turn and turn and turn but didn't start. I took it to benz, they told me it was the CPS. I changed it. It ran fine for a week, started fine, etc. Then the CL came on. So I bought about a $70 dollar code reader. It told me that the TPS was bad among other codes like the P171-P175. I took it back. This time they claimed it wasn't the TPS but rather the MAF. So I put a new one in, after market. It worked again for about a week, then the light came back on and it's idling strange. Dies at times at lights or surges suddenly. So I bought another MAF, this time a BOSCH. I put it in yesterday, the codes go away and the car runs fine. The car ran fine for a day, 50 miles or so, then today, again with the CL light and again with the codes P171 thru P175. I was doing some reading and apparently a bad TPS can ruin or give the reading that the "MAF is bad." Mercedes should have changed the TSP, it's almost at the "covered to 70k warranty" point, perhaps that's why they didn't? Don't know but I need to bring it back and tell them that it's NOT the MAF but rather the TPS, correct? Is there any way to test the TPS myself so I go in to them with extra ammo? I just don't trust them. Any help would be appreciated.

phoenix_iii

Get the problem documented before the Warranty is up (from what I've read). Why spend your own money on a new MAF, etc? Was that not covered? Is the TPS then?

enap66

The MAF isn't covered. Fine, I'll pay for that. But the TPS, that's a lot of money and some work. I'd rather have them do it. Anyway, this whole thing has been trying and I'll never buy another benz. This isn't the first silly issue I've had with them. BMW all the way, COVERED from bumper to bumper from the beginning to the end!

Glyn M Ruck

P0170 = Fuel Trim Malfunction (Bank 1)
P0171 = System too Lean (Bank 1)
P0172 = System too Rich (Bank 1)
P0173 = Fuel Trim Malfunction (Bank 2)
P0174 = System too Lean (Bank 2)
P0175 = System too Rich (Bank 2)

These idiots could not diagnose their way out of a wet brown paper bag.

The CPS & TPS might be problematic but these are all fuel trim codes. Prime causes
MAF
Vacuum leaks
O2 sensors

Generic MAFs never work on these cars - that said, are you sure that the correct Bosch MAF has been fitted. Where did the MAF come from & does it have the correct MB part number on the black plastic cover? Frequently VW/Audi MAFs are sold on the internet at good prices & suitable for Merc which is wrong. They look identical & fit. They won't work on a Benz V6.

Next steps

Was the correct CPS fitted - Check
Was the correct MAF fitted - Check
Do a throttle reset
Cancel all codes

Then drive the car and see what codes return. Let us know the outcome & we'll take it from there.

enap66

Thanks.

C24owner

https://mbworld.org/forums/c-class-w...-diy-faqs.html

look half way down in the ENGINE/MECHANICAL section

PA_Pete

I believe the TPS is part of the throttle pedal assembly. That being said, It isn't too hard to replace, that is of course, if that is the problem. But yes, it isn't cheap, I just bought one.