Hi Forum,

I have the engine failure warning light showing on my Doblo (2009, 120ps, with 115k miles) and using MES (licensed) am getting the following codes:

P0504 - Brake Pedal Switch
P0101 - Air Flow Meter Signal
P0111 - Air Flow Meter Air Temperature

I have tried resetting the faults but they are persistent and reappear straight away and I have also checked all fuses in the car and under the bonnet. All light bulbs appear to be functioning correctly (e.g. brake and reversing lamps) and the faults don't appear to have coincided with anything in particular. The car runs fine, covers a fair amount of regular motorway miles and is currently showing no other sign of problems. My MoT is due in a week and whilst I understand this is not a fail it would be nice to fix it beforehand if I can. I am also assuming that the two components have not coincidentally failed at the same time but I guess that is always a possibility.

Any advice welcome.

Kind Regards and thanks in advance

Peter

Hi again Forum,

Well it has been almost a year since these codes appeared and the car has passed another MoT and is still running beautifully albeit with the rather alarming "Engine Failure" message and chimes whenever I start up.

I did replace the brake pedal switch but this made no difference at all to P0504 so I am left thinking that this must be a wiring or fuse issue somewhere.

I have taken out all the fuses (engine bay and in-car) one by one and they all tested fine. I have also found references to the same set of codes on Brava and Alfa cars relating to wiring from the front to the back of the car but nothing that seems relevant to mine that I can see.

Does anyone have any suggestions?

Kind Regards

Peter

Is the air flow meter connected.? Is the air temp signal/reading present on live data when checking on the diagnostics.?
I wouldn't worry about the brake switch fault code as long as the brake lights work.

Thanks very much for that Thefox,

Using MES with the engine running I am getting :-

Intake air quantity signal period 0.000 ms
Air temperature (MAF) -40 'C

I guess this means taking it out and try cleaning it or perhaps a replacement?

Kind Regards

Peter

It certainly appears like the air flow meter is not working, make sure the connection is ok and the electrical connector pins are in good condition, not damaged.
If your thinking of buying another, have a look on the sensor for the part no. it may well be a Bosch unit with 9/10 digit number. This might help source it on the internet.

-40 on the iat is a default reading for open circuit and as the maf is reading 0 Aswell I would be first checking grounds and feeds on the sensor you should see a 12v feed and a 5 v feed at the sensor along with 2 signal returns and probably a ground on the 5th wire sorry don't have any pin data to hand could also be linked to the brake light switch fault Aswell as there is 2 circuit on that one of stop lamps and one for the pcm

Hi again,

Today, I removed the battery tray for better access and connected up my multi meter to each of the 4 feeds at the terminal which connects to the MAF sensor.

I appear not to be getting any voltage at all on any of the 4 wires/slots with the engine running - any ideas what I could try next?

Kind Regards

Peter

All sorted now and codes cleared

It turns out that the fuse F35 under the dash is not as "Spare" as the manual suggests.

I had at sometime used a 'spare' fuse from the top row of fuses and where the light must not have come on instantly I had not made the association when this first happened.

It's nice to be able to start the car now without the chimes and failure message and thanks for your help and suggestions.

ATB

Peter