406oc.co.uk

Have got a 406 110 HDI, D9 (I think - on 53 plate - if that helps) it was a bit slow at bottom end, after searching this (and other sites) found out was probably MAF sensor. Got a scrap joby (all numbers matched so think its the right one). thats when it went tits up.

Fitted new one no bother. but when i conected it the car starts no bother but comes up antipollution fault and the dash light is on. it also ticks over faster about 1200 rpm. it also will not rev when pedal is pressed. also does the same if i plug the old sensor in. The only way i can get the car to go is to disconnect the MAF sensor, but the car is in limp mode all the time. still says antipollution fault on screen with light on. But at least it drives.

The only thing i can think of that happened, was when i was changing the MAF sensor (In the garage) it started rainning very hard, not sure if the connector got shorted out or something (when i got back in car also noticed i must have left the bloody ignition on). everything else was all covered with there plastic covers, only thing i could think of.

If it did short could it have blown the ECU or BSI thingy.

Sorry for the 3000 word esay.

Please help

Maybe the new MAF is NAFF?

Have you tried re-fitting the old sensor to test?

Try disconnecting the battery for 30 mins to clear the fault codes from the ecu. Then see if the problem comes back, after that best bet is probably to get the fault code read as that should tell you what the ecu *thinks* is wrong.

The only thing i can think of that happened, was when i was changing the MAF sensor (In the garage) it started rainning very hard, not sure if the connector got shorted out or something (when i got back in car also noticed i must have left the bloody ignition on). everything else was all covered with there plastic covers, only thing i could think of.

It's very unlikely that the rain shorted anything out as rainwater is quite high impedance. Won't short anything.

However, having the ignition on when you disconnected the MAF sensor would have caused some consternation in the ECU.

It's more than likely, the system is in shock and won't recover until the codes are ALL reset.
I don't think the "battery disconnect" works on these as they started storing the parameters in non-volatile memory with the HDi's.

I suspect that you're faced with a trip to a KNOWLEDGEABLE mech armed with a code reader/writer.

Borrowed a friends code reader today - it's a 'memoscan U581 not sure how good it is. got something funny (I think - Not that up on electronic side)

I cleared all the codes first, then when i check again with the MAF sensor unpluged i only get 2 codes -
P0190 Fuel rail preasure sensor circuit Malfunction
P0235 Turbo/Super boost sensor A circuit Malfunction.

If i plug MAF in, clear codes to start then I get 6 codes one twice.
P0560 System Voltage Malfunction
P0190 Fuel rail preasure sensor circuit Malfunction-X2. Why 2 of the same?
P0235 Turbo/Super boost sensor A circuit Malfunction
P0120 TPS/Pedal Position Sensor A circuit Malfunction
P0220 TPS/Pedal Position Sensor/switch B circuit Malfunction


Not being an expert by any means, but this makes me think it might still have somthing to do with a short of some type.
maybe blown a fuse or a circuit some how.

I have checked all the fuses all look fine.

Is that with the old or the new MAF or both?

Thats with both - just the same with both MAF's.
I just want this sorted I am sick of following all the sunday drivers, go faster following a bloody tractor.

sounds more like a throttle potentiometer fault, clear the codes, then with the ignition off unplug the maf, start the car and see how it drives then check the faults

jameslxdt wrote:sounds more like a throttle potentiometer fault, clear the codes, then with the ignition off unplug the maf, start the car and see how it drives then check the faults

The throttle potentiometer fault and system voltage fault are only there when i plug the MAF sensor in.
with it unpluged all works fine - apart from being in limp mode that is.

have been advised to check the 5v supply too the sensors (MAF, Fuel rail and coolant) apparently they all have a common 5v supply.
not sure where the 5v comes from though. ie ECU, BSi or sone where else.

Right. Tested the 5v Idea, All fine with MAF unpluged. But When I pluged the MAF in the voltages went up to about 12v.

Now answer me that one - I am totaly PETE TONGed.

how does it run with the maf unplugged and what faults does it log, im not sure entirely but the turbo pressure control valve, maf, map are all fed by the same circuit
and the reason your voltage is going up is because there is no load on the circuit

Update:

It's Fixed, It's ****ing FIXED.

Was just rereading the posts, James (canyondust) over on tdocuk.com said that the MAF was only directly connected to the ECU. So I thought for one last dich attemt would take ECU to bits.
There it was a burnt out circuit, burnt all the way down the pcb.
So have soldered a fine wire from point to point.
Seems to work, just reset codes and came up clear.
Going to give it a little run tomorrow, down to the metro center and back.

Have you ever heard of this before James?

Thanks for all you help mate.

Well done Neil!
That must have shorted out to burn a track away!

has the car ever been jump started?
also check to make sure that the correct amp fuse is in place for the ecu