Mk2 1.9 Tdi 115 - Underboost Map Wiring Info

[Yozza]

Hi folks,

 

I've been struggling with my wife's galaxy for a number of weeks now.  It has been suffering with very little power (boost), I borrowed a reader which read the two following codes 17964 & 16485.  I did a lot of reading up (mainly on this forum) about these two codes.  And to cut a long story short I have done the following:

• Replaced the turbo with a refurbed unit from Midland turbo (great service).
• New N75 solenoid
• New MAF sensor
• New MAP sensor
• Check the pipes to and from the N75 for leaks using a vacuum pump and gauge

I still haven't resolved the problem.  When using the Torque Lite app while the engine is running I noticed that the boost reading was a constant 36psi regardless of the engine revs.  The other thing I noticed was the revs around 1300rpm were irratic (surging).

 

I am convinced the MAP sensor and/or ECU aren't playing ball.  I have check the wiring from the ECU to MAP sensor for continuity - all ok.

 

I would like to know what all four wires are supposed to do, and which wire (colour) is which.  When checking with DMM I got two of the wires reading a constant 5v, another wire was constat ~1.7v and no volt on the other wire (probably the ground).  I would of expected to see 5v (supply), 0v (ground), 0-5v (signal), not sure about the forth wire, can you any of you good folk shed any info on the wires to the MAP??? 

 

Could I have a dodgy ECU, which isn't sending/receiving the correct signal from the MAP and sending the vehicle into limp mode???

 

I am getting desperate, I even took it to the garage and they didn't know what to do with it as I've done pretty much all they would do, they said it's a job for a specialist auto electrician.

 

Any help greatly appreciated.

 

Yozza