electrical fault - wiring fault - Diesel Engines (Mk4 Mondeo) - TalkFord.com

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electrical fault - wiring fault

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#1 beardyman



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  • 11 posts
  • Vehicle Driven:Focus
  • Name:Dave
  • Location:South West

Posted 15 October 2020 - 09:21 PM

It all started after I had exhaust parts replaced, there has been loud exhaust noise and juddering feeling like that car was about to cut out.  This occurred in stop/start driving situations. 
         Electrical issues opening windows.  This was intermittent and after a few days disappeared and has not come back. 
         Light bulbs blew – replaced and fine. 
         These two could be red herrings! 
Engine malfunction P244C appeared and Investigated….
dpf vaporiser checked for blockage + resistance tested ok
pump for vaporiser bench tested ok
visable wiring around pump and vaporiser checked, fuese + relays for pump checked ok
pump is receiving live but no earth signal

car suddenly won’t start
Roadside assistance found the following after checking all feeds that go to and out of the relay when pressing the stop/start button: 
• Permanent feed going into relay = ok
• Trigger wire coming out of stop/start control module (the button).  The feed is coming out and there is a feed coming in to the relay on PIN1 = ok. 
• Checked main engine earth = ok
• Checked main chassis earth = ok
• It is not the relay that is at fault as this was swapped for another with the same configuration.
• Checked all fuses – not a feed problem, it is more of an earth problem
• Checked earths on Chassis rail = OK and clean

• What is missing from ECU there should be a “switched earth”.  I was advised when the ignition is switched on / car started it should send on the engine management side a “switched earth” to the relay to say start.  This earth is not there. If the “switched earth” cannot give the circuit an earth the components won’t work to send the feed down to the starter motor.  This is not happening due to no “switched earth”. 
The guys wire diagram was not fully detailed shows it coming from the EC it doesn’t show any connections it just goes to the “starter replay” - is there any connections?
• It is not felt to be an ECU fault and is either a wiring fault (corroded earth) somewhere or it is a connection problem somewhere
• The car can be started by bypassing the relay. 

Any ideas what it could be? 
How do I address this problem, I assume it either needs to go to main dealer or a specialist car electrician?  To ensure I am not paying for duplicate checking what if anything should I encourage them to check out?  thanks.

Edited by beardyman, 15 October 2020 - 09:32 PM.

#2 nicam49


    Little Megger

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  • 4023 posts
  • Vehicle Driven:Mondeo mk3
  • Name:Nick
  • Location:Leicestershire

Posted 17 October 2020 - 05:38 PM

Well, how about the ignition switch being faulty. If its not passing a switched earth when on - either the earth to it or the switched earth from it needs testing out.
<p><p>nicam49 2002 Mondeo TDCi Ghia X Estate mk3 pre facelift Stardust Silver+Rust.[b] 308,000+miles, but been off the road since Nov 2019 after timing chain slipped during fuel pump transplant. Awaiting return of mojo

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