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2.7 HDi and Error Code P1351 'they all have it'

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Dave-Retired   
Tue Nov 07 2017, 03:59PM

Joined: Oct 01 2009
Member No: #1
Location: Northumberland
Yes we have all read elsewhere that every car shows this code.... but should it and what is it actually for?

Via Diagbox P1351 pops up on my car when I check, even after clearing it and in the Citroen database all I can find is P1350 which relates to the Pre / Post heat relay which a web search also points to but is it the relay or a faulty glow plug throwing the error?

Sunday morning we had a heavy frost and it took a while for the engine to fire into life, churning the starter to long for my liking (have had starter issues on the Traction Avant in the past so I like to keep on top of things!)

So some old fashioned fault tracing was required. Citroen billing time to change the actual relay is 40 minutes so it couldn't be a big job?

Ordered a new relay online from World Car Parts which at just over £43.00 was worth a try and it arrived today so fitted it and took a few images to show just how easy it is to change.

The relay is buried under the fuse box but accessed from the top with a few simple tools, a crosshead screwdriver, a torq 15 driver and a 10mm socket.

1st take the fusebox cover off. Then remove the 2 screws circled which retain the Suspension ECU and simply (but carefully) fold it back towards the bulkhead.




Then the 2 screws that hold the main ECU in place and fold that back carefully (you may need something to prop it back though as it will want to fall back into place).




Now you can see the relay. There is a screw down at the bottom to remove so you can lift it up, but the wiring harness is tight.




Finally take the lock nut off the power supply and unclip the 2 connectors and take out the relay




Fitting is a simple reversal of the process and you can't go wrong with the relay connectors as they are all different and only fit one way.

Once I had mine back together it was time to test it out and.....

Yep the code P1351 came back so it must be one of the glow plugs that has failed, not the relay.

Next step is to get a set of glow plugs and change them all as at 101,000 miles it's pointless changing 1.

EDIT: oh and it took me 30 minutes to change the relay

To test the individual Glow plugs you can follow the above procedure to access the 6 way connector on the relay to use a multimeter rather than removing the engine cover and disconnecting each plug individually.

The rear of the relay is numbered to match the glow plug location with cylinder 1 at the bottom through to cylinder 6 at the top:




Why is pre / post heat important:

Postheating is used to reduce pollutant emissions during the first few minutes after starting and will reduce soot/carbon build up in the system which affects the EGR Valves and DPF.

Citroen wrote ...
The times for pre-heating and post-heating are determined by the engine ECU as a function of the temperature of the engine coolant fluid at idling speed and at altitude .

Engine coolant temperature Pre-heating duration

60c 0 seconds
10c 0 seconds
0c 4.1 seconds
-5c 5 seconds
-10c 6.5 seconds
-30c 20 seconds
Engine coolant temperature Post-heating

60c 0 seconds
40c 200 seconds
20c 190 seconds
-30c 155 seconds
Parameters which can interrupt the postheating:

* Coolant temperature above 40 °C
* Engine speed greater than 3050 rpm


For details on changing the actual glow plugs have a read of this thread: - Click Here -
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10 User said Thank You to Dave-Retired for this Post :
 Ciaran (07 Nov : 17:23) , Eric (07 Nov : 18:05) , 321dave (07 Nov : 20:58) , Tjensen (07 Nov : 23:40) , cruiserphil (08 Nov : 12:43) , gmerry (08 Nov : 12:59) , vaho (08 Nov : 13:20) , eke (08 Nov : 18:40) , e3steve (09 Nov : 14:58) , userpco (12 Nov : 11:32)
Ciaran   
Tue Nov 07 2017, 05:22PM
Joined: Mar 31 2017
Member No: #3087
Location: .
I have that fault too, have done since I bought the car more than 6 months ago now.

According to my cousin, a time served Peugeot mechanic, 'That P1351 is on every PSA diesel engine I've ever seen'.

Maybe a slight exaggeration but he's come across a hell of a lot of them which still log the fault even after the relay and glowplugs are changed.

I seem to recall reading on here that there could be issues changing glowplugs on the V6s where they like to seize in solid and then break and / or ruin the threads on removal. Not a job I'm looking forward to but one that's coming to us all I suspect.
cruiserphil   
Wed Nov 08 2017, 12:46PM

Joined: Jan 24 2010
Member No: #38
Location: Celbridge
Great post Dave,

Best regards,

Phil C.
gmerry   
Wed Nov 08 2017, 01:00PM
Joined: Dec 11 2009
Member No: #21
Location: Scotland
Dave, yes great post and a very good method for checking status of each glow plug.

thanks
vaho   
Wed Nov 08 2017, 01:19PM
Joined: Jun 25 2015
Member No: #2228
Location: Tallinn
Well I do not have that fault and I understand that the relay itself it´s almost never the cause of the fault, it´s the faulty glow plugs which are not diagnosed directly by the ECU. I also heard that the fault is triggered only when all three from one bank are faulty, one faulty plug does not show. Can not confirm that though.
Nevertheless - great post, thank you.
Swalleau   
Wed Nov 08 2017, 09:46PM
Joined: Apr 09 2017
Member No: #3097
Location: Bournemouth
Mine had this fault too. Whilst it was having rear ABS sensors and an EGR valve Robert found two dead glow plugs and they are all now new.

I've not done the job, but people seem to be wary of the job because there is a risk of breaking them. A cold engine seems to be the LEAST optimal condition though.

I wonder if there is a correlation between EGR valves and failed glow plugs?
Dave-Retired   
Thu Nov 09 2017, 08:53AM

Joined: Oct 01 2009
Member No: #1
Location: Northumberland
Swalleau wrote ...


I wonder if there is a correlation between EGR valves and failed glow plugs?

Well logic would dictate that if the glow plugs weren't working then when cold the engine is not heating up fast enough due to restricted post start heating so soot and other by products of combustion are in a higher concentration for longer which could impact other parts of the emission control system including the EGR valves.

It's not air temperature related either, post heat is triggered by Coolant temperature.

How long it could or would take to have an impact though is the unknown factor, but on my car with 2 recently fitted new EGR valves I'm going to try and reduce the risk of them failing again by replacing the glow plugs. A set of 6 Bosch ones only cost £43.50 which is a lot less than the cost of an EGR and fitting it.
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2 User said Thank You to Dave-Retired for this Post :
 Ciaran (09 Nov : 11:50) , e3steve (09 Nov : 14:59)
321dave   
Thu Nov 09 2017, 06:43PM
Joined: Sep 09 2011
Member No: #614
Location: Dublin
Dave-Retired wrote ...

Swalleau wrote ...


I wonder if there is a correlation between EGR valves and failed glow plugs?

Well logic would dictate that if the glow plugs weren't working then when cold the engine is not heating up fast enough due to restricted post start heating so soot and other by products of combustion are in a higher concentration for longer which could impact other parts of the emission control system including the EGR valves.

Thread carefully Dave, when fitting the Glow plugs!!

It's not air temperature related either, post heat is triggered by Coolant temperature.

How long it could or would take to have an impact though is the unknown factor, but on my car with 2 recently fitted new EGR valves I'm going to try and reduce the risk of them failing again by replacing the glow plugs. A set of 6 Bosch ones only cost £43.50 which is a lot less than the cost of an EGR and fitting it.



Thread carefully Dave, when removing the old glow plugs!! I was about to change mine when my radiator started leaking and my efforts were suddenly diverted to a more urgent task. But I did start when I was replacing the timing belt as it was more accessible st that time. But I had trouble applying very little torque to the first one, I decide not to continue (got a bad felling) and continued to complete the timing belt instead. Car still starts anyway with no issue, even though it has the code showing as well.
e3steve   
Fri Nov 10 2017, 11:45AM
Joined: Jan 21 2013
Member No: #1163
Location: Warsash, Hants & Palma de Mallorca, Spain
This is a brilliantly informative thread, guys!
 

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