Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   PeachParts Mercedes-Benz Forum > Mercedes-Benz Tech Information and Support > Tech Help

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 02-14-2006, 05:48 PM
Secret Squirrel's Avatar
Registered User
 
Join Date: Mar 2005
Location: Commerce City, CO
Posts: 74
Smile Oxygen Sensor grounded to chassis on 300SEL?

I went to put a new O2 sensor on today and the old one had a big copper wire with a red jacket attached to a screw into the chassis. It made it a real chore to even turn the wrench with that dang wire smashed down against the threads.

Why would someone have done this? Some type of bypass on the O2 sensor? It wasn't getting as good of mileage as I thought it should have... 17-19 on long cruising trips and occasionally the check engine light would come on after it hadn't been driven for a couple weeks and needed some carbon burned out of the system.

But why the ugly ground wire attachment??

__________________
(2) 1988 300 SEL W126
Reply With Quote
  #2  
Old 02-14-2006, 06:54 PM
Moderator
 
Join Date: Mar 2000
Location: Gainesville FL
Posts: 6,844
The sensor voltage of the O2 sensor is very small by comparison to other sensor readings. In many instances a .2v voltage drop is inconsequential. In a O2 sensor it is s deal breaker. An O2 sensor voltage of .5v needs to reference the same ground as the control unit. One of the surest ways to do that is make real sure both are referenced to the same thing: chassis ground.

In newer 4 wire O2 systems the ground for the sensor is brought back to the control unit to assure they are the same. I presume someone was just making sure.
__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician
Reply With Quote
  #3  
Old 02-15-2006, 12:46 PM
Secret Squirrel's Avatar
Registered User
 
Join Date: Mar 2005
Location: Commerce City, CO
Posts: 74
Steve thanks for the reply,

So is this something I should worry about? I had put it all back together (without the wire) and it's running fine as far as I can tell... no check engine light or anything.

__________________
(2) 1988 300 SEL W126
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -4. The time now is 11:36 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page