Fault code P1250-P1256 (2 Viewers)

[Warrenpfo]

March 2003 Amazon 4.2 TD.

Today the amber engine warning light has come on when I have been driving. The light illuminated shortly after I noted a significant decrease in power when accelerating from standstill or when accelerating out of a roundabout. The power loss would be recognised then about 2 seconds later the light would appear and stay illuminated until I stopped the engine and restarted it - then it would be reset and may not appear for a few weeks. The power loss noted in advance of the warning light illuminating is only periodic - the engine power is always restored soon after the light comes on. I shorted the wires and gor a fault code 34 which is detailed below.

Where do I start and has anyone else suffered this?
Today I did 350miles with no problems so its a funny one.
Someone mentioned it might be the turbo with adjustable pressure controlled by a vacuum actuator (from Aug 2002). Is the vacuum solenoid OK?

 

[Bawlz]

Someone mentioned it might be the turbo with adjustable pressure controlled by a vacuum actuator (from Aug 2002). Is the vacuum solenoid OK?

The vanes may be gummed up and getting stuck in the Turbo. If they get stuck one way, it will be slow to spool, but boost fine at higher RPM. If they get stuck the other way, it will spool fast, but choke at higher RPMs. But because it is a VNT, there is a lot of area in between as well. If you have a hand vacuum pump that does pressure and vacuum, you can manually actuate the vane actuator to see if the vanes stick.

It could also be a bad/dirty air flow meter, and the ECU is pulling boost because it's not getting a correct value. Same goes for if the ECU isn't getting the correct values for the intake pressure or turbo pressure (the chart seems to indicate there are sensors for both intake and turbo).

Hope this helps, I don't have any first hand experience on a 4.2, but based on prior experience as a tech, this is what comes to mind first.

 

[Bawlz]

Oh yeah, VNT:

 

[Warrenpfo]

Thanks chaps, will start with the airflow meters and then have the vanes pressure tested to check if they are sticking.

One thing to ask is how easy is it to clean the vanes?? Is it a DIY job as i may just do this anyway or should i take it to a turbo man.

 

[Bawlz]

Not really a DIY job, unless you know how to disassemble a turbo, I'd take it to the turbo man.