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 03-21-2019, 10:38 PM
Registered User
 
Join Date: May 2007
Location: Grayson, GA
Posts: 20
1990 W124 300E Checkengine light at low RPM

I have been getting a check engine light at low (idle) rpm. When checked the codes are for the #14 pin the following:
2: Fuel pump relay (circuit 87) not functioning
3: TN/TD signal (RPM) interrupted
4: Output for oxygen sensor heater control defective
5: Output for air injection pump control defective
6: Output for kickdown switch control defective
12: Output for A/C compressor control defective
13: Excessive A/C compressor clutch slippage
When I check the wiring diagram most of these go through the Engine Systems control unit. Could it be this unit or actually all of these things? How to check?
The check engine light goes away upon acceleration.
__________________
Buddy Ligon
1985 300SD
1969 280SE Cabriolet
Reply With Quote
  #2  
Old 03-21-2019, 11:02 PM
Registered User
 
Join Date: Sep 2001
Posts: 677
What is the idle RPM?
Battery good or great?
What is the charge voltage at idle?
I'm asking/thinking the idle RPM is too low causing low voltage, there is a charge output problem (regulator) or a bad OVP relay.
Remove, clean and reinstall the grounds at and near the battery.
Good luck!!!
__________________
Does a Caddy stretch? No, but a Mercedes bendz.
Reply With Quote
  #3  
Old 03-22-2019, 12:40 AM
Registered User
 
Join Date: May 2007
Location: Grayson, GA
Posts: 20
reply

Thank you.
Idles at 500-700 with trans engaged and 700-800 in neutral
Voltage in neutral has been 13.7 to 13.9 at the battery haven't checked with trans engaged.
Battery seems solid less than year old Mercedes battery. Starts easily etc.
Ill checked the terminals for the corrosion and give it a good clean.
I was thinking at the low idle maybe the alternator was dropping to low for all the systems to working properly but I thought that was more on newer cars. I did take unscrew the grounds in the engine bay and clean each of them for good contact to the body point. I know on my other Mercs that grounds have a lot to do with having things work properly especially the ones behind the instrument cluster and in one case the antenna aerial ground for the speedo (other model)
__________________
Buddy Ligon
1985 300SD
1969 280SE Cabriolet
Reply With Quote
  #4  
Old 03-22-2019, 12:42 AM
Registered User
 
Join Date: May 2007
Location: Grayson, GA
Posts: 20
reply

Oh and did check the OVP works great.
__________________
Buddy Ligon
1985 300SD
1969 280SE Cabriolet
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 01:23 AM.


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