Technical EGR P0401 P0402 1.3 diesel: some answers.

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Technical EGR P0401 P0402 1.3 diesel: some answers.

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I know there are quite a number of posts re the dreaded codes above and much of the following has already been written about them elsewhere, but here are my experiences and some answers that could save some grief.

Daughter's 2008 1.3 Sport (pre Euro 5) threw up these codes at 67 000 miles: P0401 and P0402, which seemed to indicate a blocked or poorly functioning EGR.
Therefore I changed the EGR, and that is not easy, and not recommended for the feint-hearted. It did the trick even though the old one only had a light dusting of carbon (more on that later), or so I thought. Four months and 3 000 miles later codes back again and car goes into "get you home" mode, which it does, just!
Research showed that commands are sent to the EGR and these can be shown and recorded using OBD Car Doctor app, the monitoring of the performance of the EGR is done, not by the EGR itself but by separate sensors and these are:-

MAP sensor located to the left rear of the manifold and held on by just a self-tapping screw.

DPFE sensor located not far from the MAP sensor but located on the bulk-head and secured by a 10mm spanner size nut and a Clic-R clip.

Both, if not working correctly, can throw the codes which apparently blame the EGR!

Neither of these are expensive or difficult to replace so I changed them first but still no joy, and OBD graphs of EGR command very 'spikey'. At that point I decided to take the old EGR apart and found that the valve operated by the solenoid was sticky in a couple of places rotationally in the closed position; the plunger of the solenoid is spring-loaded so even when the plunger is pushed out when there is a p.d across the connecting pins, any resistant force of the valve keeps the plunger retracted so the valve does not open.

Noting all this I did the following:-

Note: sizes of nuts, bolts etc. are spanner sizes in this description.
The air box comes off very easily, the only fastener is a Clic-R band where the MAF is on the side of the air box.
Battery and tray were removed, the ECU comes away with the tray after disconnecting it, there are 2 13mm bolts and a 13 mm nut (deep socket needed) spanner size securing the tray, also there is a 10mm nut, under which is an earthing tag and another that secures a vacuum switch bracket, that too has to come off along with some cable clips, it's all rather obvious when you look.

Now I took off the EGR electrical connector and using a long 4 mm Allen key on a 3/8" socket released the three Allen machine screws, the original had Torx screws, that meant the solenoid could be moved out of the way and inspected and it was fine.

The stem of the EGR valve was now in view and using a chop stick I tried to push the valve in, a larger force than should be necessary was required. I used electrical contact cleaning spray on the valve and worked in in and out until it felt as though the force needed was less and I then sprayed high temperature grease all round the valve and in the cavity; the valve was pushed and released very many times until I could feel very little force was needed, and that to overcome the light spring.

Once everything was replaced the car was tested and since doing this procedure the engine light has remained unlit, the OBD EGR command graphs now were much smoother with easier transition from level to level. I only wish I had tried this (it took about 3/4 hour) the first time instead of replacing the EGR as that took many hours (it's all at the back of the engine) and so much has to be done to remove and replace it, the "flexible" metal tube to the back of the manifold is very difficult to line up and attach for example, that's stuff that nightmares are made of.
 
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My 08 1.3 sport has just clocked 65k. I'm semi worried I'm about to encounter a similar issue, but relieved I've a good explanation/remedy to show my mechanic if/when the time comes.

Thanks for this well written post.

Tom.
 
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