C5 fault codes - Help

johntom · Post by **johntom** » 11 Apr 2011, 20:31

Hi
I recently blanked the egr valve off my 2004 C5 110 hdi, using a plate bought via ebay. The car ran better, however after the first journey (20 miles) the engine management light came on with the service light and the message 'anti pollution fault'. I have just connected my code reader and got the following codes:
po341 Camshaft position sensor A - bank 1 CKT range performance,
po402 EGR Fow excessive,
po400 EGR Flow malfunction

I cancelled the codes and the light stayed off for a few miles/stop/starts - then came on again with just code po341 and po402 ?

Would the EGR blanking cause this or are the codes not connected ?
Should I have pulled and sealed the vacuum pipe to the EGR when blanking off the EGR as I just left it attached ?

All help greatly appreciated !

Post by **myglaren** » 11 Apr 2011, 22:01

Yes, the vacuum pipe should be blanked off.

Have you stalled the engine at all - the PO341 code will be generated if you have.

johntom · Post by **johntom** » 11 Apr 2011, 22:29

Hi
I have stalled the engine but not since I cleared the codes ?
both codes appear together after a short journey.

are the camshaft sensors prone to failure or is it likely to be connected to the egr code?

wheeler · Post by **wheeler** » 11 Apr 2011, 23:35

If you have put a blanking plate in the EGR valve then it wont make the slightest bit of difference wether you leave the vac pipe connected to the EGR valve or remove it & plug the pipe as long as the pipe is not left detched & open at the end.
If the camshaft sensor was faulty the engine would not start as it needs the cylinder reference to let it start, disconnect it & you will see it wont fire up although if it is disconected while the engine is running it wont make any difference to the way it runs. As myglaren says this fault is usually caused by stalling the engine or the engine cutting out for any reason other than turning the key off.

BX · Post by BX » 12 Apr 2011, 00:36

After 2002 many HDI engines detect a malfunctioning EGR valve by measuring the airflow and possibly the manifold pressure. When the ECU sends the signal to open the EGR valve the measured airflow should be lower than the calculated airflow which would be with the EGR valve closed. Result:- engine management fault and anti pollution fault if you have blocked or disabled the EGR. You can successfully block the EGR on earlier HDI engines either by fitting the plate or disconnecting the vacuum pipe. Same goes for most other makes of diesel engine as well.
Hope this makes some sense. Don't ask me exactly which models can and cannot be blocked. I don't know. All I do know is that the early 8 valve 2L can and 2L 16 valve cant.

Post by **myglaren** » 12 Apr 2011, 07:04

Sorry, if the vacuum hos is reattached to the blanked off EGR then it is effectively plugged anyway.

johntom · Post by **johntom** » 12 Apr 2011, 12:21

Hi
Why would the camshaft sensor fault appear at the same time as the Egr fault ?
If the car is a 2004 mk1 hdi 110 would it be an 8v, the chassis code is RHZ ?
As a last resort I will remove the blanking plate and try again?

wheeler · Post by **wheeler** » 12 Apr 2011, 17:31

What was the reason for blanking it in the first place ?

johntom · Post by **johntom** » 12 Apr 2011, 17:56

Hi
just that it was supposed to improve bottom end pick up (which i think it as). Also the car developed a juddering/shaking when started from cold every morning, this hasn't happened since the egr was blanked off. The only disapointment is the engine mgmt light and anti pollution message.

johntom · Post by **johntom** » 15 Apr 2011, 22:49

After 2002 many HDI engines detect a malfunctioning EGR valve by measuring the airflow and possibly the manifold pressure. When the ECU sends the signal to open the EGR valve the measured airflow should be lower than the calculated airflow which would be with the EGR valve closed. Result:- engine management fault and anti pollution fault if you have blocked or disabled the EGR. You can successfully block the EGR on earlier HDI engines either by fitting the plate or disconnecting the vacuum pipe. Same goes for most other makes of diesel engine as well.
Hope this makes some sense. Don't ask me exactly which models can and cannot be blocked. I don't know. All I do know is that the early 8 valve 2L can and 2L 16 valve cant.

I removed the EGR blanking plate, cleared the codes and the car has run all day without the engine management light ! so it doesn't like being blanked off.
Unfortunatley the slight juddering on tickover has returned on a few occassions and the po341 code always returns although it doesn't activate the EML?
How could the EGR valve cause the car to judder/shake on tickover, is the valve open or closed on tickover ?

AndersDK · Post by **AndersDK** » 16 Apr 2011, 21:31

Sorry to butt in with my dirty 5pence knowledge

But if you leave the EGR hardware as is - with all connections intact - it should work with a blanking plate.
What error code(s) do you get when blanking the EGR ?
AFAIR there is some sort of pressure metering in connection with teh EGR.
This may be your teaser when trying the blanking option.

The ever re-occurring judder error on tickover could be a defective - or wet - air flow meter, as this is used for EGR control.
That would fit the bill if it only occurs on EGR normal setup.

Hope this is at least slightly useful

cachaciero · Post by **cachaciero** » 16 Apr 2011, 21:51

BK had it about right, that's what the MAF does measure flow into the engine, the ECU "knows" what the inlet "clean" air flow should be when the EGR valve is operative, with it blanked off the numbers don't match so.... error. Least that's the way I understand it on later engines, don't really understand why it doesn't work like that on earlier engines probably because EGR systems have been refined over the years to meet Euro iV V etc.

cachaciero

johntom · Post by **johntom** » 17 Apr 2011, 23:33

AndersDK wrote:Sorry to butt in with my dirty 5pence knowledge

But if you leave the EGR hardware as is - with all connections intact - it should work with a blanking plate.
What error code(s) do you get when blanking the EGR ?
AFAIR there is some sort of pressure metering in connection with teh EGR.
This may be your teaser when trying the blanking option.

The ever re-occurring judder error on tickover could be a defective - or wet - air flow meter, as this is used for EGR control.
That would fit the bill if it only occurs on EGR normal setup.

Hope this is at least slightly useful

Hi
the error codes I get are po400 and po402, relating to excessive air flow and flow malfunction. How can i test the air flow meter ?
many thanks

AndersDK · Post by **AndersDK** » 17 Apr 2011, 23:57

The AFM is a plug- in unit to the intake airduct.

Dig it out and clean & dry it internally, then do a visual inspection.
It can only be tested using a Lexia running in live data mode.

cachaciero · Post by **cachaciero** » 18 Apr 2011, 21:27

johntom wrote:Hope this is at least slightly useful

Hi
the error codes I get are po400 and po402, relating to excessive air flow and flow malfunction. How can i test the air flow meter ?
many thanks

If you have the EGR blanked of that is exactly what I would expect, the ECU has no way of detecting that the flow through the EGR valve is zero, however it will detect the increased flow through the MAF (because the EGR is blanked) and post it as an error.

I would suggest putting the engine back to standard clear the error codes and see if they come back before worrying to much about the MAF.

cachaciero