Coolant temperature sensor fault causing low boost

Jonas Majauskas jmajau at
Wed Jul 14 11:06:47 EDT 2004

On Sun, 11 Jul 2004, Phil and Judy Rose wrote:

> At 10:02 PM -0400 7/10/04, TM wrote:
> >I've recently had a problem with low boost and poor
> >boost ramp-up, seeing only 10psi constant after a long
> >time of WOT. Just after observing this problem intermittently
> >a few times, I had a radiator neck failure, so I wasn't sure
> >if the two events were connected.
> >
> >Now following the radiator replacement, I've found that I still
> >have a low boost problem after the engine is hot- pulled codes
> >and found coolant temperature sensor, intermittent fault.
> >
> >Doing the Bentley diagnostic, it seems like the multifunction temp
> >sensor is fine, this doesn't really make sense.
> I'm not sure what the Bentley "diagnostic" is. My own diagnostic
> procedure is simple: pull the connector off the MFTS. If that cures
> your low boost problem, replace the MFTS.

ECU error code (using blink codes) 2312 means the real coolant temperature
sensor on the back of engine block. Brett already described the procedure.

I believe MFTS failure should give "engine overheat" or similar error, not
the "coolant temperature sensor".

I got this 2312 code a few days ago (along with hard engine start).
Checked resistance between pin 30 and pin 45 in the ECU plug - no
resistance (open circuit). Checked the sensor on the engine block - 600
ohms (depends on engine temperature). Closer look to connector revealed
the source of problem - the plastic inside connector was cracked.
Maybe there is too hot for plastic to last more than 14 years :)
Replaced the connector, and voila! Check engine light now blinks out
4444, or "no fault codes stored".

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