Can ANYONE help me on this one????
Thread Starter
Junior Member
Joined: Apr 2009
Posts: 43
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2004 C240
Can ANYONE help me on this one????
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.
Thread Starter
Junior Member
Joined: Apr 2009
Posts: 43
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2004 C240
MAF
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!
Super Moderator
Joined: Jun 2008
Posts: 19,942
Likes: 192
From: Llandudno, Cape Town, South Africa
late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
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.
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.
MBWorld Fanatic!
Joined: Sep 2005
Posts: 5,769
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From: NJ
'08 E550 4Matic
https://mbworld.org/forums/c-class-w...-diy-faqs.html
look half way down in the ENGINE/MECHANICAL section
look half way down in the ENGINE/MECHANICAL section
Senior Member
Joined: Aug 2008
Posts: 273
Likes: 6
From: SE PA
2001 C320
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.
