Normski

What happens to the car after it has hit the boost cut?

While driving tonight (in the manner a scooby should be driven) my car (1996 Sti RA) hit what i think was the boost cut. And afterwards the check engine light came on, and it wouldn't boost over ~0.5 Bar without cutting. I drove home gently, switched off then turned the engine back on again. The CEL was off so i went for a drive and it was back to normal.

I then read the ECU fault codes and it gave me #45 which is the pressure sensor.

My boost controller is set to ~0.9 Bar (on my gauge which has unknown accuracy). I understand the boost cut for this model is 1.1 Bar, is this correct?

So my question is, is this behaviour normal? or does it require further investigation?

Thanks.

wrc78

Well if you were not able to go beyond 0.5bar without cut, you likely had a MAF load cut, which happen only in the case of an ongoing MAP CE (which equal to an out of bound reading, that is above 2.15bar absolute or below -0.29bar ABSOLUTE).
Therefore, your MAP sensor might have had or still have a problem (defective harness, sensor ?)

And in the case you did encounter a boost cut which should indeed be at 1.1bar (save any exceptionnal atmospheric depression), there should not be any more consequence than a temporary cut, as I guess it might only happen on your car (which I take as not being heavily modded ?) during very rare sustained overshoots. Note that a boost cut does not set a MAP CE.

Regarding the memorized CE, it is just there for the picture, it has no incidence afterward.

Normski

Thanks for the info wrc78.

That was the first time the car hit what i thought was the boost cut, so i was unsure if the CEL and a limp home mode was supposed to activate.

I don't think the boost was anywhere near 1.1 Bar (according to my gauge) so i was also unsure of the accuracy of it. My boost controller has always kept the peak boost at the level i set, without spiking. So that clears that up.

Is the fault code of 45 refering to the MAP sensor then? Because i've also seen it described as 'pressure duty solenoid' so i wasn't sure what it was. I'll have a look at the MAP sensor and see if there is anything obvious. How much is a new MAP sensor anyway?

Thanks.

wrc78

The MAP sensor is indeed code 45.
The pressure duty solenoid should rather be code 44, if it has to be understood as being the wastegate duty solenoid.

I do not have any idea of the price, but as I previously stated, I am not convinced your sensor itself would require a change; you might want to have the harness investigated before, aside with some ECU monitoring.
Also, a simple cleaning might fix the problem.

I actually do not have any idea of the MAP sensor failure rate, but I would not bet it being that usual.

Fabrice.