P0103 code Passat 2003 AWT engine

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Re: P0103 code Passat 2003 AWT engine

Postby Tronic » Sun Oct 15, 2017 5:59 pm

Hi again!

Well, the MAF should not be connected in this measurement. If I had the MAF connected it would have fooled me. Think of this, if there is an internal faut in the MAF, as in this case, it would be 12 volts on pin 5, sure as a letter from Royal mail. The only way to be confident that there is nothing wrong in the wire harness or an internal ECU fault, is to disconnect the MAF, then you can safely point out where the fault is. :D

The 12 volts at pin 5 - output from MAF - resulted in an air mass no less than 240g/s :lol:
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Re: P0103 code Passat 2003 AWT engine

Postby Technician » Sun Oct 15, 2017 7:29 pm

Tronic wrote:Hi again!

Well, the MAF should not be connected in this measurement. If I had the MAF connected it would have fooled me. Think of this, if there is an internal faut in the MAF, as in this case, it would be 12 volts on pin 5, sure as a letter from Royal mail. The only way to be confident that there is nothing wrong in the wire harness or an internal ECU fault, is to disconnect the MAF, then you can safely point out where the fault is. :D

The 12 volts at pin 5 - output from MAF - resulted in an air mass no less than 240g/s :lol:



Tronic wrote:Hi again!

Well, the MAF should not be connected in this measurement. If I had the MAF connected it would have fooled me. Think of this, if there is an internal faut in the MAF, as in this case, it would be 12 volts on pin 5, sure as a letter from Royal mail. The only way to be confident that there is nothing wrong in the wire harness or an internal ECU fault, is to disconnect the MAF, then you can safely point out where the fault is. :D

The 12 volts at pin 5 - output from MAF - resulted in an air mass no less than 240g/s :lol:


Looking at the wiring diagram and the checking procedure, as you rightly point out pin 5 should not have 12 V present when the MAF is connected. As an 'electronics expert, I do mean you and not me' :) you could make oneself a variable voltage regulator quite cheaply and turn the voltage down on pin 5 to a typical 1.4 V at idle.

I don't know if you have access to the same technical data as me, but if you haven't I'll share it with you;

ECM terminal 29 connects to the MAF terminal 5 > this should read at idle (MAF connected) 1.4 V

ECM terminal 53 connects to the MAF terminal 4 > this is a 5 V output from the MAF connected

ECM terminal 27 connects to the MAF terminal 3 > this is a ground connection

MAF terminal 2 should have a battery feed 12.6 V via fuse 34 (15 A) and ignition control relay K20 (K46)

I've never actually tried to test a MAF sensor disconnected, my experience and advice given over the years has always been test the inputs and outputs from all sensors/actuators connected unless directed otherwise.
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Re: P0103 code Passat 2003 AWT engine

Postby Tronic » Sun Oct 15, 2017 10:04 pm

Thank you Technician!

Yes I have same data, pinout for the ECU connector and wiring diagram. Yes, it could be done with for instance the LM317 voltage regulator, but lowest possible voltage (well, the circuit itself could be modified to go from zero) is 1,2 volts. Possibly it could be done with a 7805 voltage regulator and a resistive voltage divider, cause I think the impedance is fairly high and hence low voltage drop in the divider. I guess it is not an easy task to bench test a MAF in order to check if it is ok or not, but it could be done just to see varying voltage when air flows through it. No doubt it could be a good classroom demonstration :lol: I

If the customer did not throw away the MAF I will crack it open and put it under my microscope ...why? Well, just out of curiosity. :lol:

Thank you Technician and all other for helping me out with the P0103 code!! :D
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