The engine light has come on on my 2007 MK3 Sport and is showing code PO403 which is the EGR valve. The car has done 11365 miles since new. My trusty local garage has checked it over and can find no typical EGR symptoms. The car runs perfectly. On top of that it passed it’s MOT yesterday with flying colours, so there would not seem to be an emissions problem. The code was deleted, but the light has come back on.
My local garage thinks the EGR is probably suffering from some carbon deposits due to the low mileage and don’t recommend replacing, especially given that the car is running fine. I’ve also noted that the EGR valve is very difficult to get at and involves removing lots of parts which is another reason for leaving alone if everything else is fine.
I have seen that cans of EGR cleaner are available from Wynn’s for application via the air cleaner intake and wonder if this may be worth a go to get the engine light out.
Has anyone else experienced this problem and if so how did you resolve it? Also, has anyone used EGR cleaner and if so how effective was it?
From my experience it’s the electronic side of the valve that fails. If you check the resistances across the windings inside it you’ll probably find one of the out of specification. That’s the cause of the light.
It affects the operation of the valve. I’m not 100% sure which way they fail but on NB cars the go to short circuit and I’ve known them to take out ECUs with them…
just a thought, its not in relation to your cars EGR code, but I wondered if you have tried disconnecting the cars battery to see if that helps.
The reason for my thinking is because I had the passenger airbag light coming on and flashing, not every time I drove the car but on most occasions it would. By coincidence I wanted to spray the air cleaner sensor with electrical cleaner as the car was never driven much before I bought it and I thought it might be contaminated with dust.
The battery was disconnected for about an hour while I was cleaning the sensor (you need to know your audio code when you do this, or dis activate it, so read the audio manual before)
I think all the capacitors/sensors/fault codes in the cars electrical system drain down during the time of disconnection so you need to leave the car disconnected for a hour. Once all is reconnected and engine is started the system goes through a various checks and if no faults are found then no engine light or in my case- no airbag warning light.
That was about 3 months ago and all is still fine so it worked for me.
Many thanks Robbie and Rodders. I’ll get the resistance checked for sure. If the resistance turns out to be OK, do you think it’s worth trying some Wynn’s EGR cleaner?
P0403 is an EGR stepper motor fault code, not a EGR flow fault code. The ECU is basically looking at the voltage on the EGR stepper motor wires and checking the pin voltages as the EGR stepper motor coils are turned on and off. An open circuit, a short to power or short to ground will cause the fault code to be stored.
I’ve uploded the inspection procedure for the EGR valve into the Technical folder of the Downloads section. It’s in the sub folder called Technical Information.