Engine immobilised

alanlondon · Unread post by **alanlondon** » 05 May 2022, 20:19

Hell Razor5543 wrote: 05 May 2022, 13:05 Something that might be worth trying is to clean the blades of the fuses. A couple of months ago my C5 threw up a suspension fault. After faffing about a bit I found the fuse blades were very tarnished (not burnt), which had increased the electrical resistance. I did a BSi reset, and (while the battery was disconnected) I popped each fuse out and (using a model rail track cleaning rubber) cleaned the blades (they went from dull grey to shiny silver), and she has not had an issue since.

I will be replacing all the necessary fuses with new; which may mean all of them as my dashboard fusebox is nothing like shown in the handbook. I've no idea what half of them do and, I am not going to diagnose the function of them all. I have already used contact cleaner on them, but as I have hundreds of fuses sitting around, why not?

Hell Razor5543 · Unread post by **Hell Razor5543** » 05 May 2022, 21:43

Watch out for the SHUNT 'fuse'. It is NOT a fuse; it is used to switch the vehicle from 'showroom' to 'customer' mode, and in 'showroom' mode the vehicle will not work properly (as some equipment will be turned off). The SHUNT fuse is one of the 'cabin' fuses, and is typically large and grey. The following link shows the various fuses/fuse boxes, and the SHUNT 'fuse' is in fuse box C;

https://imgvehicle.com/citroen/c5-i-dcde/fuse-box

alanlondon · Unread post by **alanlondon** » 05 May 2022, 22:59

Hell Razor5543 wrote: 05 May 2022, 21:43 Watch out for the SHUNT 'fuse'. It is NOT a fuse; it is used to switch the vehicle from 'showroom' to 'customer' mode, and in 'showroom' mode the vehicle will not work properly (as some equipment will be turned off). The SHUNT fuse is one of the 'cabin' fuses, and is typically large and grey. The following link shows the various fuses/fuse boxes, and the SHUNT 'fuse' is in fuse box C;

https://imgvehicle.com/citroen/c5-i-dcde/fuse-box

Hi James,

Thanks for your reply.

I'm aware of the SH fuse! Not intending to touch it.

The website appears to show a later car than mine; certainly nothing like my under bonnet fusebox and, the interior fusebox is also different. Wish I could find an image that matches mine.

alanlondon · Unread post by **alanlondon** » 05 Jul 2022, 07:41

Sorry to drag this old thread up again! I have had some health issues which have been somewhat of a problem...

So now back to making the old bus go again.

Snap on scanner will not communicate with ECU.

5 volts at Mass air sensor.

Fuel pump tested ok but no power to pump.

No spark.

All fuses replaced with new. BTW I eventually found a diagram which matched my fusebox as the handbook didn't show mine! If anyone has the same issue it was here: https://fuseandrelay.com/citroen/c5.html

Lovely sound of electricals working in the engine bay when ignition is on!

Further ideas welcome. (But guessing I could do with a decent Lexia!).

Unread post by **xantia_v6** » 05 Jul 2022, 12:07

Is the immobilizer light showing when you try to start it?

alanlondon · Unread post by **alanlondon** » 05 Jul 2022, 12:17

xantia_v6 wrote: 05 Jul 2022, 12:07 Is the immobilizer light showing when you try to start it?

No. Only flashed up when first stopped.

wheeler · Unread post by **wheeler** » 05 Jul 2022, 12:50

Do you have the VIN so i can take a look at a wiring diagram. Wont be able to do this till later this evening.
Im still thinking this is likely a BSM issue.
In the meantime unplug the 16 pin grey connector on the under bonnet fuse box (BSM) and check pins 11 or 12 (there will probably only be one of these wires present) look closely at both the pin in the fusebox and in the plug for signs of overheating, it usually has signs of discolouration, this wire is the output to the fuel pump & this is a known issue with mk1 C5’s however i have only ever known it to affect diesel models.

alanlondon · Unread post by **alanlondon** » 05 Jul 2022, 13:18

wheeler wrote: 05 Jul 2022, 12:50 Do you have the VIN so i can take a look at a wiring diagram. Wont be able to do this till later this evening.
Im still thinking this is likely a BSM issue.
In the meantime unplug the 16 pin grey connector on the under bonnet fuse box (BSM) and check pins 11 or 12 (there will probably only be one of these wires present) look closely at both the pin in the fusebox and in the plug for signs of overheating, it usually has signs of discolouration, this wire is the output to the fuel pump & this is a known issue with mk1 C5’s however i have only ever known it to affect diesel models.

Having read about this on the forum, I have already checked and, there is no sign of any overheating whatsoever. Pins clean and no melted plastic! Wiring intact and as new(ish).

I'll post the VIN when I return home.

alanlondon · Unread post by **alanlondon** » 05 Jul 2022, 15:23

VIN Number:

VF7**************[VIN obfuscated, can be read by forum staff]

wheeler · Unread post by **wheeler** » 05 Jul 2022, 19:11

On the under bonnet fusebox Pin 11 of the 16 way grey connector and pin 1 of the 16 way black connector can you see if there is 12v at both these wires when you crank the engine over? check with everything plugged back into the fusebox.
Can you confirm that you have checked all the fuses including the maxi fused on the underside of the under bonnet fusebox?

alanlondon · Unread post by **alanlondon** » 06 Jul 2022, 12:56

wheeler wrote: 05 Jul 2022, 19:11 On the under bonnet fusebox Pin 11 of the 16 way grey connector and pin 1 of the 16 way black connector can you see if there is 12v at both these wires when you crank the engine over? check with everything plugged back into the fusebox.
Can you confirm that you have checked all the fuses including the maxi fused on the underside of the under bonnet fusebox?

Hi wheeler,

Thanks for checking that out. Only residual voltage on both those connections >0.2V.

I did check the maxi fuses but am happy to have another look. However, I am assuming (a dangerous thing to do!) that I have just been testing the fuel pump and coil connections. If so, will be interested in your thoughts.

wheeler · Unread post by **wheeler** » 06 Jul 2022, 16:08

Both of those wires are powered up by an internal relay inside the under bonnet fusebox the pin 11 on the grey plug is the output to the fuel pump & pin 1 on the black plug is the power supply to the injectors, oxygen sensor heaters & a few other things. Out of curiosity you could try back feeding one of these wires with a fused 12v feed. When you do this the fuel pump should run & hopefully the engine should be able to start up. If the engine is able to start like this then I would suspect the under bonnet fusebox is at fault.

alanlondon · Unread post by **alanlondon** » 06 Jul 2022, 16:28

wheeler wrote: 06 Jul 2022, 16:08 Both of those wires are powered up by an internal relay inside the under bonnet fusebox the pin 11 on the grey plug is the output to the fuel pump & pin 1 on the black plug is the power supply to the injectors, oxygen sensor heaters & a few other things. Out of curiosity you could try back feeding one of these wires with a fused 12v feed. When you do this the fuel pump should run & hopefully the engine should be able to start up. If the engine is able to start like this then I would suspect the under bonnet fusebox is at fault.

Spot on wheeler. Pin 1 to battery.

Immediate start. (and how lovely it sounded!).

Is there an electrical genius on the forum who can repair these?

wheeler · Unread post by **wheeler** » 06 Jul 2022, 19:16

Thats great news & pretty much confirms the fusebox is at fault. As for repairing them, I have never tried & dont know how easy it is to source internal parts, I would imagine the repair is pretty simple if you can solder.
A new one is £346 inc VAT from Citroen

alanlondon · Unread post by **alanlondon** » 06 Jul 2022, 20:42

wheeler wrote: 06 Jul 2022, 19:16 Thats great news & pretty much confirms the fusebox is at fault. As for repairing them, I have never tried & dont know how easy it is to source internal parts, I would imagine the repair is pretty simple if you can solder.
A new one is £346 inc VAT from Citroen

Really?

I'd be happy to just buy one, but have been told they are NLA.

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