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p1586 on 2.2HDi
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kgw   
Mon Oct 06 2025, 10:46am
Joined: Nov 15 2023
Member No: #5399
Location: Versailles
 Hello,

As a background, my C6 DW12BTED4 FAP automatic (4HS) has been suffering from various limp mode issues (P0087, P0093, P1113). Hopefully, a fuel filter change will cure that (although I hear it could also be due to wiring to the fuel pressure sensor). Also, I've had throttle-related DTCs and engine lights, which I dealt with by installing a metallic gear to fix the worn out plastic cog inside the throttle (the sensor position DTC keeps coming back, but at least there's no engine light and engine stops smoothly when I turn ignition off.

Recently, I started experiencing sudden engine shut-downs. I thought they were linked to this fuel pressure issue but the car has now fully stopped in a street. DiagBox says there's a permanent p1586 which I had not seen before: "alimentation capteur régime moteur, recopie vanne EGR, recopie vanne turbine 2, recopie papillon réchauffeur air admission", indicating low voltage on the power supply to crankshaft position sensor, EGR valve position sensor, turbo 2 valve position sensor and intake air heater flap position sensor, along with volatile errors linked to the above. It suggests a wiring issue but I don't have a schematic nor can I find a common connection to these components in the pinout.

I can't clear it and the car won't start. Can anyone give me some clues ?

Pinout: Link deleted by Admin due t0 'Trojan' report
C6Dave   
Mon Oct 06 2025, 01:47pm


Joined: Oct 01 2009
Member No: #1
Location: Northumberland
 I couldn't find an error code doc for P1586 however a Google found this which hopefully may answer your query: - Click Here -
Website
MGmike   
Mon Oct 06 2025, 04:58pm

Joined: May 21 2017
Member No: #3151
Location: South Queensferry
 I'm going to go out on a limb here and say you have a BSM relay failure that supplies all those sensors.

There is also the possibility one of the sensors has a short which is dragging the supply voltage down.

Unplug the EGR first and then each sensor in turn until the rail pressure is the last one and see what happens.

Good luck
kgw   
Tue Oct 07 2025, 01:44pm
Joined: Nov 15 2023
Member No: #5399
Location: Versailles
 Thanks a lot for the helpful advice. Never thought of that. I assumed that all sensors took ref voltage from the ECU and I now realise that's wrong.

A schematic would help but I'll try your method anyhow.
kgw   
Tue Oct 07 2025, 06:17pm
Joined: Nov 15 2023
Member No: #5399
Location: Versailles
 What a mess around the back of the engine.


I found the PCV hose (3) disconnected from the cam cover and I now understand from looking at EGR valve pics on eBay, that the EGR electric connector (valve+sensor) is right underneath that hose. Maybe that's the root cause. I'll check tomorrow.

It might also explain why the French MOT inspector found oil coming under the car from that area.
kgw   
Mon Oct 20 2025, 12:57pm
Joined: Nov 15 2023
Member No: #5399
Location: Versailles
 I've investigated a lot and it turns out that there's a short inside the doser throttle (in front of the engine). I had installed a cog repair kit but the metal glued cog fell off and interferes.

There's lots of oil inside so I suspect the CCV isn't working properly (well, the hose was disconnected).
MGmike   
Mon Oct 20 2025, 05:03pm

Joined: May 21 2017
Member No: #3151
Location: South Queensferry
kgw wrote ...


There's lots of oil inside so I suspect the CCV isn't working properly (well, the hose was disconnected).


Oil in the intake pipework is also symptomatic of impending turbo seal failure!

I'm not saying it "will fail" just that it "could be failing".

It's also difficult to check how much oil is bypassing the seals.
 

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