C5 Mk 1 drove into a flood resulting in immediate fault messages

[aspire_helen]

A few nights ago i rounded a sharp corner on a country road and "hit" a flooded section (with some force) at about 30 mph. The car's momentum carried it through the flood which was only about 20-30m long, and it drove on out the other side in a few seconds. However, two fault warnings appeared immediately: 1. ABS/ESP failure 2. Engine anti-pollution system faulty. I was only a few miles short of my destination, so i drove on. A mile or so later, the engine seemed to lose a little power but picked up again. On arrival, I restarted the engine. The ABS/ESP fault had disappeared, but the anti-pollution warning persists. The engine runs and idles fine, but I have yet to take it for a run. I will put Lexia on it tomorrow. I suspect the temporary ABS failure resulted either from the wheel sensors being compromised, or possibly some aquaplaning (ie wheels spinning at different speeds). I am hoping the anti-pollution warning proves to be a clearable temporary fault. I am wondering if the sudden cooling of the exhaust may have caused irregular exhaust gas temperature readings (pre and post catalytic converter). Or perhaps some water in the exhaust/DPF being interpreted as a blocked filter? Problem is....I am 200 miles from home! And, yes....I now carry Lexia in the car, and a good job too. If I cant clear the fault, the ECU manual suggests I might have 200km grace before it goes into "limp home" mode and a 2200rpm engine limit.
Any ideas or experiences?

[RichardW]

If you've got the kit just read its mind, anything else is pure speculation!

[Estately]

An easy check would be to take the top off the air filter box to see if any water got into it during your cruise. The filter can be lifted out for inspection.

It may have left the filter material deformed and water in the filter material, although probably dried out now, will change the characteristics and reduce the capability for air flow into the engine.

If your car no longer has the engine undertray then water could have been thrown up into the engine bay and into the engine air inlet.

A new engine air filter is easy to change.

The filter box should have a small hole down in the bottom to assist drainage for circumstances where more water than expected has been ingested.

The drain hole can get blocked by dust picked up just driving about. Not sure that the average service would see this attended to.

Hope that helps.
Andy.

[aspire_helen]

Andy, good call. The air filter was sodden and the well in the base of the air filter box was full of water. I expect that would account for 2 Lexia faults:
“Temporary Fault. Flowmeter signal. Short circuit to positive”. (P0100)
“Temporary Fault. Flowmeter signal. Air flow too high coherence”. (P0101)
Interestingly, the ECU has started to try and regenerate the DPF. ”Regeneration assistance request = active”. I have cleared the faults and will give the car a run on Sunday.

[myglaren]

I had this on my C5 Mk 1 when the wheel arch liner exploded and the induction hose that is normally behind it sucked in lots of water and grit, ruined the MAF and the air filter, the horn on the filter box was full of muck and water.
You might rescue the MAF with a carb cleaner spray. Be very careful with it as they are very delicate, drop it or touch the fine wires with anything and it is wrecked.

[Rp0thejester]

If waters got on the MAF sensors then that's toast, can't touch them let alone get them wet. When I unplugged mine it also removed the DPF blocked warning and gave me power back. I'm assuming the lack of input from the sensor made the DPF think there wasn't enough air flowing through so it must be blocked.

[myglaren]

This was mine after being drowned.

(I wondered what the thing with the red writing on it was. A Blackspur multitool that had been my dads. It is still on my desk )

[aspire_helen]

I must have been lucky - the MAF was wet but otherwise clean and undamaged, so I removed the housing and dried it against a radiator. The air filter took 48hrs on a radiator to dry out fully. I put them back together (in driving rain) and set off on the 200mile motorway trip home. Performance fine (57mpg at 60mph cruise over the Pennines with headwind and a bike on the back), and no warnings. Hoorah! We stopped off for a celebratory take-away 2 miles from home. Restarted the engine, drove out of the car-park and....ABS failure warning! The b*****d must have heard us. "Electrovalve internal" again....grrrr.