Technical 500 1.3 Multi-jet P0402 - Potential fix

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Technical 500 1.3 Multi-jet P0402 - Potential fix

bradds

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Hi All

Just thought I would share my experience finally rectifying the dreaded P0402 (EGR excessive flow) error on the wife’s 08 500 1.3D Multi.
The P0402 error started to appear intermittently about 6 months ago, after a code reset, it would sometimes be fine from anywhere between a few days to a few weeks before coming back (and going into limp home mode).

During the course of the issue, I did the following - in chronological order

1) Replaced MAP sensor – No Joy.
2) Replaced DPFE Sensor – No Joy.
3) Removed EGR solenoid and worked the valve – As described in post on this forum. – No Joy
4) Removed and cleaned the EGR valve and checked for blocked passageways etc. – None found and was in relatively clean condition – This procedure is an absolute Nightmare, so not recommend for the faint of heart.

After all the above and many hours of wasted time, the code STILL appeared.
One thing I did not check and turned out to be the cause of the intermittent fault, was the pipe from the exhaust to the DPFE sensor…. It was clogged with carbon at the exhaust end of the pipe, restricting flow to the DPFE sensor. Why I did not check this first, God only knows, as it is far easier to fix than any of the above.

Anyway, it has been fine now for several months, and I just wanted to post on here to maybe help someone who gets the P0402 code and was thinking about changing all the bits as described. As failure of any of the parts listed can potentially cause the issue, I learnt the hard way and it would be worth checking the exhaust to DPFE sensor pipe FIRST – before embarking on a crusade.
 
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Welcome to the forum and thank you for using your first post to share such information and experience :)

The most interesting part for me is that I recognise that P0402 code from a completely different vehicle - similar situation though - a flap in the exhaust designed to bypass the muffler was stuck open, and the back pressure sensor readings were therefore incorrect. Just goes to show that such knowledge can be useful when shared, thanks again for your time doing this.

-Alex
 
Hi All

Just thought I would share my experience finally rectifying the dreaded P0402 (EGR excessive flow) error on the wife’s 08 500 1.3D Multi.
The P0402 error started to appear intermittently about 6 months ago, after a code reset, it would sometimes be fine from anywhere between a few days to a few weeks before coming back (and going into limp home mode).

During the course of the issue, I did the following - in chronological order

1) Replaced MAP sensor – No Joy.
2) Replaced DPFE Sensor – No Joy.
3) Removed EGR solenoid and worked the valve – As described in post on this forum. – No Joy
4) Removed and cleaned the EGR valve and checked for blocked passageways etc. – None found and was in relatively clean condition – This procedure is an absolute Nightmare, so not recommend for the faint of heart.

After all the above and many hours of wasted time, the code STILL appeared.
One thing I did not check and turned out to be the cause of the intermittent fault, was the pipe from the exhaust to the DPFE sensor…. It was clogged with carbon at the exhaust end of the pipe, restricting flow to the DPFE sensor. Why I did not check this first, God only knows, as it is far easier to fix than any of the above.

Anyway, it has been fine now for several months, and I just wanted to post on here to maybe help someone who gets the P0402 code and was thinking about changing all the bits as described. As failure of any of the parts listed can potentially cause the issue, I learnt the hard way and it would be worth checking the exhaust to DPFE sensor pipe FIRST – before embarking on a crusade.

Update.

Apologies, I should have updated this post a long time ago.

In addition to the original post, I also found that the metal pipe that runs from the bottom of the ERG Valve into the air intake manifold had very high carbon build up, almost to the point of complete blockage. It would be worth removing this and checking it first before changing any sensors or removing the ERG valve. My ERG valve had little to no carbon build up in it so I assumed the pipe from it to the intake would be the same … I WAS WRONG. The build up was mainly at the top where it enters the manifold, so even if you remove the ERG and check the bottom of the pipe without removing it (like I did), it would appear to be clear..ish.

This is well worth trying first as it costs no money, only time (if you do it yourself of course).
It is a bit fiddly working round the back of the engine trying to get the pipe back on once cleaned, but best tackled from underneath.

WARNING! Always remove the Diesel particulate filter (DPF) from the exhaust (or just disconnect it) BEFORE Turing the engine on after refitting the cleaned pipe. If you don’t, Carbon that has worked loose in the air intake WILL find its way into the filter and block it. Then it’s a day or two pressure washing the filter and then trying to get all the water out…. I learnt the hard way. Mind you, it was like a new filter after I had finished, but it turns a few hours job into 3 days. Not worth it unless yours is bad in the first place.

After doing this I have had no issues with it whatsoever. Over 2 years.
Hope someone finds this info useful, and saves you a lot of time from banding your head against a brick wall and getting screamed at by the missus; after breaking down on the motorway twice :-(
 
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