PO300 code

Talk about the 406's electrical system, what wires do what, how to add extra functionality, etc.

Moderator: Moderators

Post Reply
Waldo155
1.6 8v
Posts: 18
Joined: Thu Mar 23, 2023 5:06 pm

PO300 code

Post by Waldo155 »

I recently had water in the drivers side footwell which caused quite a few electrical issues, mostly back to normal now but I am getting a recurring P0300 code which can sometimes drop the car into limp mode. Scan the system and remove the P0300 fault and off we go again for a bit.

The odd thing is I do not have a misfire (2.0 HDI 110 by the way), flow correction is pretty high on number 3 and 4 injectors at idle but straighten up to around 1.2 when the revs are above 2500 rpm. This P0300 fault only shows up on my original/standard ECU which was fine before the water ingress, I have a re-mapped ECU with immobiliser off etc which I have swapped over to since this trouble started, now, using the re-mapped ECU I never get the P0300 code and the car never drops into limp mode!

Could the original/standard ECU have thrown a permanent P0300 wobbly due to the water ingress, at least now the car has dried out the alarm has stopped going off on its own at stupid o'clock in the night :lol:

I do have a replacement standard ECU that needs my keys coding to and am hoping once this is done it will be "things back to normal". I like the remap but my missus hates it, well mainly hates my driving when it's fitted to the car :roll:

Any thoughts on this would be very much appreciated, Paul 👍
frog
2.0 Turbo
Posts: 378
Joined: Sun Aug 24, 2014 12:18 pm
Location: Netherlands

Re: PO300 code

Post by frog »

Your best option is to connect the PP2000 software which will show the details of the fault.

It could very well be that this fault needs an explicit clearing; I think I have had to do this once or twice (but I never had this P0300 fault though... random misfires seem not very applicable to HDI).
Current "fleet":
2003 406 Estate 2.0HDi 110 - 7 seater - just hit 690.000 kms :cheesy:
2001 Citroen Saxo 1.6i 8v 100

Previously owned:
2000 406 Sedan 2.0 HDi 90
2000 406 Coupé 2.0i 16v 138 - Riviera Blue

PP2000 user, can help with faults / diagnostics in the Netherlands.
Waldo155
1.6 8v
Posts: 18
Joined: Thu Mar 23, 2023 5:06 pm

Re: PO300 code

Post by Waldo155 »

Thanks Frog 👍👍
Post Reply