mrbsponge

from what i have been told and researched so far Q31 seems to be O2 heater section of the ecu.

for some weird reason i keep blowing these, we are going to pull my whole engine harness and test it.

but my O2 isnt even plugged in, nothing is touching it or anything but my new ecu almost caught fire because of it.

a friend just bought one(p28) off ebay and when he opened it, same thing happened to this one.

it doesnt throw a CEL, and seems to keep the car in open loop, kinda like the O2 isnt even there


any one have this happen to them

hoggy

Let me guess, you just put the engine harness on and you are now having these problems???

Now take the IAT plug and the PCV valve plug and switch them. Should fix the problem. I'm pretty sure q31 has to do with the IAT. Hope that fixes your problem.

Did you find replacement parts for that? If so where?

mrbsponge

i had a couple spare ecus with other problems.

are you sure its the IAT, cause it threw a code for that and i changed it and the code went away, when i pulled the IAT, the plastic probe looked kinda melted like wax dripping from a candle.

where can i find something to diagnose the ecu board

093turbo16

iTrader: (2)

I believe he is correct, this happens when you plug something in wrong..

Joseph Davis

Yup, and it ***** more than Q31 most of the time. I have seven ECUs with blown Q31, still looking for the fix for most of them.

mrbsponge

what PCV valve plug?? you mean like the PCV as in pressure control valve system, i didnt think there was a plug there???

i have the right plug there, now on the IAT, i busted out the book and looked it up, i have the right wires,

when i put in a new ecu and crank the car up, the Q31 starts glowin like a bitch and on the last p72 it actually had a littel flame and desoldered itself.

WEIRD THING IS THE CAR RUNS PERFECT????

Joseph Davis

Then run it. I've one that fries the big cap, C16, right next to it everytime I try to replace it, but still runs fine. I use it on my beater, don't trust it in anybody else's shizzle. I've driven from NC to PA to OH and then back home in one big circle, 200 miles to Taylorsville once a week for the last month, and everywhere inbetween for a sum total of 12K on this ECU, so my caution is probably not warranted.

HRTuning

They mean the IAT sensor plugged into the PCS wiring, not PCV... This is usually the common cause and you'll continue to fry Q31 and possibly fry IAT sensors until you plug them into their correct spots...

093turbo16

iTrader: (2)

I two have one running on a P75, we swapped harnesses and the problem went away. But I still use the P75 on that car. I tried 3 P28s in there and they all worked fine after the harness conversion. GSR motor in LS car.

UberTeg

Q31 is under the bridge on my pr4

riddlinkid1986

IS q31 important? Im geting ready to hit the dyno in a week an half, an was looking at my used p28 i bought an that q31 is toast! I un-sodered it an looks like maybe the bord might be bad to. (due to Q31 heating up)

I will be getting tuned with uber or Crome.

iv searched an searched! an some people lean twords leave it off, not needed.

my car is a 2000 civic si, with the p2t ecu, being converted to obd1 with p28!

Any info helps! im new to chipping an dont want to waste my time on a bad ecu. unless there is a chance...

HatchEh2

you need it.

if the Q31 fries, your ecu DOES NOT see the IAT sensor, thinking the temp outside is always -40*F ... causing you to run VERY rich and the ecu will not adjust the correct amount of fuel when the temp changes with different seasons during the year...

so in other words if your tuned at 67*F weather... your car is only gonna perform that good in 67*F weather... your ecu cannot adjust accordingly.


grab a q31 out of any other ecu and solder it in.

then this time, plug the IAT in right

boosted k20

Q31 is for the purge solenoid. it doesnt have anything to do with the IAT sensor circuitry. if Q31 is fried the ecu is still good. like mentioned above, if u plug in the PCS plug into the IAT senor, then Q31 will fry and also the IAT sensor itself might have gotton fried. just connect the engine harness plug in the right location and replace the IAT senso IF you are throw n code 10

HatchEh2

i stand corrected


my tuner always told me it was the that way, but that does make sense, it would not read the IAT because its still plugged wrong, DUUHH

if you switched them back and your IAT is NOT fried then, your right, it would be fine.. i just replace the Q31 anyway.