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Discussion Starter · #1 ·
Hi Guys,

I have a Corsa C SXI which I recently had serviced. The engine management light was on and the mechanic said it was due to the Mass Air Flow Sensor (MAF) so I had this replaced (with a bosch). However the management light still appears and the car is not running to its full potential.

-low power when accelerating (especially uphill)
-stalling at low revs
-jolting during gear changes

After looking on some forums I think the problem may be the earthing of the wires, (a common problem in vauxhall cars), requiring the earth wire to be "re earthed".

Does anyone have any idea how to do this? or know how much this might cost me to get done at a garage?

Any help would be greatly appreciated.



149 Posts
As a starter I would say unplug the electrical connector from your MAF. The ECU works by measuring the volume of air flow going through the MAF and adjusting the fuel trim to match. If your MAF is kicking out dodgy signals this will cause the jerking you are experiencing. Unplugging the MAF will make the ECU use a pre-defined table of air flows and return your driving experience to a normal one, albeit with the engine management light constantly illuminated.

Secondly you need to find out why it's giving those signals. It can only really be three things;
1. Faulty MAF (you have replaced this so unlikely)
2. Faulty Wiring from MAF to ECU
3. Faulty ECU (also unlikely but certainly possible)

It is most likely the wiring and this can be tricky to troubleshoot if you don't have the wiring diagrams. I've no doubt you can get these from somewhere on the forum. Once you have it it's a case of using a multimeter to test the wires and repair the faulty one.

1,479 Posts
One i just sent to someone else...should apply to you to...Fred

Hi there, see if we can work this out, my Haynes manual says thos

1 brown and blue signal or earth
2 red and white live for ambient air temperature sensor
3 brown earth for ambient air temperature sensor
4 red and white suspect 5 volt reference wire
5 brown and green signal or earth

so earth is either pin 1 or 5, my guess is pin 5, brown and green, these colours seem different to yours, vauxhall usually use Brown for earth, white for ignition...So if you test the wires with a multi tester, i think the air temp sensor live will be 12 volts, that's pin 2, pin one seems to go to earth, should be brown, so discard those two, pin 4 should have 5 volts on, ignition on, which leaves you 1 and 5, well what you can do is with the plug on put you meter to pins 1 and 5 in turn, one should show negative, an earth, the other should be 0.5 volts at idle and 4+ volts at full throttle snap what ever...hopefully its working well enough to tell you which is which, all the 3 wires on the MAF sensor go to the ECU....i guess one of them earths through the ECU....good luck...if that sensor voltage goes from 0.5 to 4+ volts then the sensor is working anyway....good luck from Fred in Essex.

what colour is the earth wire please.
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