406oc.co.uk

My 2000 406 HDi 110 just broke down while driving. The engine suddenly stalled and I'm not able to start it anymore. I got fault codes P0403, P0510 and P0243 showing up running Torque app.
The engine cranks over but there is no life. Tried to clear the codes but they showed up again immediately after trying to start the engine.

The codes explained should be;
P0403 Exhaust Gas Recirculation Control Circuit Malfunction
P0510 Closed Throttle Position Switch Malfunction
P0243 Turbocharger Wastegate Solenoid A Malfunction

Anyone got any idea if any of these codes could be the actual problem or if it could be something entirely different?

Help is very much appreciated!

You might just have lost one of the supplies to the ecu - worth checking all the fuses, particularly F26, 27 & 34 in the engine fusebox

None of the fuses in the engine fusebox are blown.
There's no humming from the lift pump and no fuel pressure when I turn the ignition on or try to start the car, but I guess this could be related to ECU fault and not a failed pump resulting in these fault codes?!

I had something similar on a Citroen Xsara HDi 90 years ago - the car stopped because the lift pump wasn't running and the fault codes suggested an egr solenoid valve failure.

The wiring to the lift pump goes through the fuse (F25?) immediately before the pump motor. I got it going temporarily by removing the fuse and putting a +12v supply into the side of the fuse holder connected to the pump

I now have strong suspicion towards the dual relay in the ECU box.
There is no power at the terminal of fuse F25, and from beeping with multimeter that terminal is connected to terminal 4 on the dual relay. Terminal 4 on the relay have no power when I turn on the ignition or crank the engine. I tested with putting ground and +12v on the relay and it clicks but there is no power on terminal 4.

Does this sound logical to you? I think I'm gonna try and get a new relay ASAP so I can eliminate this possible cause.

*have you checked the Inertia cut off switch..

Yes, the intertia switch seems ok. I've ohm'd it.
Got the car running now supplying +12v to the F25 fuse terminal.
The EGR and wastegate solenoid fault codes are there still but I guess that is a result of the faulty relay.
Gonna try and get a new relay tomorrow. If that solves the problem I will be thrilled

Got a brand new relay today and it immediately solved the problem and cleared all the fault codes.. very happy now

Good news, hope that's the end of it.

Hopefully this won't happen to you, but I changed the double relay too and it ran perfectly, for a whole day, then went back to square one.
I never found my problem, but proved I had two points in the loom that should have been connected together and somehow were not anymore. I just joined them together and the problem never returned.

I hope too
I feared there was some earthing problems or splits in the loom but hopefully it was just the relay. I could tell from the production date on the relay that it had never been changed before. The car has now run 320' Km or 198838 mi.

What kind of fault codes did you get when there was a split in the loom?

I had the same fuel pump not running problem and a code indicating egr solenoid valve problems.
I reason this was due to the absence of one of the feeds to the ecu, which therfore did not 'see' any voltage on the connection to the egr valve when performing its power on, self-test routine. The ecu would interpret this as an open-circuit egr valve.

I see..

I think in my case all the faults were generated by the failed relay as I understand that the relay is not only responsible for power to the fuel pump but is also controlling the EGR and wastegate solenoid.. or am I wrong?

This is a great fix and a good reference for future owners on here, any chance someone can explain or show where this double relay is for future reference?

Imagine how much money a garage or auto electrician would charge trying to pin-point this sort of fault as the fault codes are completely misleading

The double relay is in the ECU box in the engine bay. The ECU and double relay is mounted in a large black plastic box next to the wiper wash tank. The relay is of maroon color, is 15 pin and has a relay diagram on it which helped me testing the relay function outside of the car. The part number in my case was 1920-7L which is a relay used in many Peugeot models.

this fix is for non mux cars