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Re: TQC boost problem?

>As you correctly said, the boost gauge on the dash takes it's signal from
>the ECU. I tried your suggestions re trapped boost but having removed the
>hose from the pressure sensor the gauge still reads overboost i.e last three
>segments of display light up. One thing I did try was to plug the hose and
>start the motor.
>Result....no difference: still reads overboost and still running VERY lumpy.
>Next step was surgery. I opened the brain and disconnected the three pin
>connector from the pressure sensor, started the motor and HEY PRESTO now got
>a smooth idle and seems to rev normally! Reconnect sensor...back to old
>It appears as though the sensor has failed in the overboost position.
>Out with multi-meter. No continuity between centre pin and either left or
>right pin while applying pressure OR vacuum to sensor. Continuity between
>left and right pin while applying both pressure and vacuum. I don't know
>what reading I should be getting but I would have thought the resistance
>would vary.
>I've been told the sensor cannot be bought....you must buy the complete brain?
>Starting to panick at this stage...I believe brains are REAL expensive!
>I drove the car gently this afternoon with the sensor disconnected but its
>not performing very well probably as the brain connot now vary the timing
>depending on pressure or vacuum. However at least it is running and useable.
>The sensor is marked   HITACHI PS2-02 Pressure sensor. The brain is MAC-01
>Where to from here????????

Hey I have a similar problem with my 87 5kCSTq, except that my boost
gauge(digital) always reads 0. The gauge works as I got it to read when I
injected a signal. I haven't really worried about fixing this yet because
everything still seems to be operating fine. The only symptom I can think of
is a bit of surging on accelerating.
 I figure the only thing affected is informational, would be nice to have
though, also the annoying check engine light comes on because of this. I
read the code and it said bad pressure sensor.
The only reason I haven't fixed it is because the local wreckers doesn't
have a brain I can try. 
Is there any other reasonable way to buy one? 
I haven't opened the brain up yet to see if it's repairable. Prolly should.

Burl Vibert
87 5kCSTq