I got code 31 from the onboard diagnostic light. The check engine light never comes on abnormally but when I short the dianostic port it gives code 31.

What is the drawback of it?
Will I blow my engine? I never notice the engine knocking and I am prett sensitive to any engine noise.
Or will the engine just got worse performance/mileage because the ECM would not allow ignition timing to advance as far as normal?

I just hate to tear all the intake and injector apart to gain access to the knock sensor. I notice the wire are a bit chafed when I did the valve seal but I did not think to check or replace it at that time. I just tape the wire back and slap everything back together.

I would clear the code and see if it comes back.
If it does, it's because the ECM is seeing a problem in the wiring/sensor path to ground. I don't know about Mitsubishi, but many manufacturers use a shielded wire to the sensor. If it is chewed up, it could short to the sensor shield ie. low resistance. If it's not shielded, ECM is seeing high resistance ie. open wire.
it should bee easy to check. I'd also check for any grounds at the intake/heads that could create a problem in the "ground loop" that the ECM is looking at.
Either way, since the ECM is seeing it, you probably won't see timing advance, and may actually see "Limp home" mode from the ECM ie. you aren't going to run worth a dam, and you need to repair it.
Kary

</font><blockquote><font size="1" face="Verdana, Tahoma, Arial, Helv, Helvetica, Sans">quote:</font><hr /><font size="2" face="Verdana, Tahoma, Arial, Helv, Helvetica, Sans">Originally posted by Big Blue:
<strong>Either way, since the ECM is seeing it, you probably won't see timing advance, and may actually see "Limp home" mode from the ECM ie. you aren't going to run worth a dam, and you need to repair it.
Kary</strong></font><hr /></blockquote><font size="2" face="Verdana, Tahoma, Arial, Helv, Helvetica, Sans">Should the check engine light came on all the time if the engine run in limp home mode? My light does not came on all the time. It run for a few second after you turn the ignition key but then stay out.

Performance wise it still the same since I got it 3 years ago. Which why I am a bit loss right now.

I'm not sure of the software on that rig, it may not set a "full time" check engine light. You will have to use your best judgement on this one, but I would get to it soon.
Kary

If the knock sensor is like the one in the Starion, you'll get a lot of induced extraneous signals if the ground shield is broken, and it may trip the error code that way. I'd check the shield for continuity before I replaced it. You can make a new shield with the shield from coax, but be sure you silver solder it. The knock sensor is just a piezoelectric generator, a quartz crystal that's inuslation suspended, but it quits if the epoxy potting melts out, and the signal is so weak that it has to have the shielding. There's a test fo r the one on the Starion that involves bopping a t/b mounting stud with a hammer to simulate detonation and you look for ignition retard at constant throttle/vacuum.

Thanks for the info Eddy. I will check into that.