My daughter's 2004 Polo 1.4 with BKY petrol engine has this code (P0402) showing on my Gendan code reader. I can't find a Polo site that I can get info like Briskoda - any suggestions?

I have cleaned out what I think is the EGR valve situated at the n/s rear of the engine on the inlet manifold. There were 4 torx screws holding it down. A small amount of carbon deposit, which came away easily with a little brake cleaning fluid, was removed but I couldn't see any blocked holes which some suggested could be the problem.

The light stayed of for about 50 miles then came back on! Any idea what to try next?

Some have tried Lamda sensors, new EGR valve and even replacement catalytic converters ( £500?) and had the light back on in a few days.....

Please let me know what to try next rather than replacing a lot of components only to have the light come back on later. By the way, it runs really well so doesn't have any affect on performance.

I think the EGR valve is in front and it is kept with 2 screws, probably you cleaned the throttle body? If you disconnect it might need to re-adapt it. You might try to clean the MAP sensor with some isopropanol.

Thanks. What does 're-adapt' mean? What/ where is the MAP sensor? If I find out I'll sort it!

Adaption is when the engine's ECU sends postional demand signals (drives the flap) to the throttle body to drive it to both end stops (limits) and then uses that information taken by a pick off signal sent back to the ECU so that the ECU can use this to correctly move the throttle body under different conditions/demands placed on the engine. The MAP sensor is the Manifold Absolute Pressure measuring device - it is calibrated to read the inlet manifold pressure in Bar(a) as opposed to Bar(g). This sensor is bolted on the RHS (O/S) of the inlet manifold. It has been said that if you switch the "ignition" on and wait a few minutes - don't touch the accelerator etc, the ECU will perform adaption - to check that listen to the throttle body after switching the ignition on without starting the engine - you should hear the flap getting driven open and then shut if the ECU is performing adaption.