The Mitsubishi Pajero Owners Club®

Bigwatta1710 · Posted: Thu Dec 13, 2018 9:04 Post subject: Help please with fault code p1298

Hello all I have a 2007 mitsubishi shogun 3.2 auto lwb which keeps going in to limp mode and shows up with fault code p1298 overboost I have checked rod on to turbo which is moving freely and put on new map sensor and new emission valve but still the same there is no smoke engine is good

Has anyone any ideas to help caus this is driving me mad Sad

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theron · ** Joined: 31 Aug 2011 Posts: 50 Location: Warwick

Have you checked to see if your inlet manifold is full of oily soot? In particular check the pipe from the MAP Sensor to the inlet manifold. The pipe can get clogged up at the manifold end and prevent the MAP Sensor from sensing the manifold pressure.

Bigwatta1710 · Posted: Sat Dec 15, 2018 21:40 Post subject:

Yes it was in a quite a mess I took of top part of manifold and separated bottom manifold caus I could seem to get rest of manifold to come off even though I removed all bolts all parts were cleaned and put back on and also made sure all pipes were clear

I have also removed turbo and cleaned was in quite a state now moving freely but still get same fault code under hard acceleration

theron · ** Joined: 31 Aug 2011 Posts: 50 Location: Warwick

The workshop manual has this information:

Code No. P1298: Variable Geometry Turbocharger Control System Malfunction (high pressure)

Check Condition : Engine is running

Judgment Criterion : Actual boost pressure is higher than target boost pressure by more than 6.7 kPa

So it sounds like you are getting too much boost. A decent scan tool should allow you to view the manifold pressure: At full acceleration at 3000rpm the boost pressure should be in the range 178.9 to 188.2 kPA

I would then check the wastegate actuator using a manual pressure pump. The actuator should start to move at 126.0-131.4 kPA. Also check the rubber hoses to the wastegate actuator.

You have checked the rod moves OK, this rod is the 'Swirl Control Valve' and alters the angle of the vanes in the turbo.

Bigwatta1710 · Posted: Sat Dec 15, 2018 23:59 Post subject:

Is the rod you are on about the one attached to the turbo the turbo it is moving freely I have not checked with vacuum pump but I do have snap on diagnosis and it seems to go to 187kpa at full throttle but on my tool there is a other boost pressure readings of 162kpa but this one didn't seem to alter much the live data vtn target boost is at 99kpa at idle and 188kpa at full boost 🤔🤔
I have also replaced vacuum hoses to map sensor and waste gate actuator
Do you know at what kpa the turbo actuator should hit the maximum stop

theron · ** Joined: 31 Aug 2011 Posts: 50 Location: Warwick

Not sure what the 162kPa value is either but if you're getting 187kPa and the target is 188kPa then that sounds fine.

When exactly does the engine go into limp home? Is it while you are on full throttle or is it when you lift off?

There is a VGT solenoid that controls the vacuum to the VGT actuator which is connected to the rod coming out of the turbo. This rod controls the vanes inside the turbo to direct more gas flow into the turbine. When the solenoid is switched off and the vacuum lost the rod should return by means of a spring.

This thread has a similar problem: https://www2.pajeroclub.com.au/forum/showthread.php?t=55805

For them it was *beep* in the VGT solenoid (caused by a missing dust cap) that caused it to leak air to the actuator when it should have been closed. They cleaned it.

Bigwatta1710 · Posted: Sun Dec 16, 2018 9:58 Post subject:

It happens when on full throttle usually when rev is at 4000 rpm in 3rd gear I have replaced the solenoid valve bought new one from millner 4 x4 not cheap at a £130
I was thinking of putting a bleed valve between map sensor and inlet manifold to try and stop overboost but not sure if it would work