4wd light from hell

[DBar]

ok i have 4wd when the light is off and when it turns on i only get rear tire fire.

ok so i have done all the usual stuff to try to fix my problem. She throws code 21. Throttle sensor or circut. the following is a list of what i have done to fix my problem

beed the system.. done
check error code.. done
replaced sensor.. done
calibrated to .5V ign on and idle.. done
checked that is sweeps from .5 to 4.2 at WOT.. done
checked grounds.. done


I have taken note of when the light comes on and what i did just before it comes on.
The light will come on at random and at anytime. it seems to more commomly come on when...
the car is up to temp
just after i put on the brakes for a light or something
when its damp or wet (raining)
more commonly at night, like 8 out of 10 times it will be at night

other things of note are..

no other lights come on.
when the light comes on its always only error code 21.
it only ever comes on if the car is in motion it seems.
if i turn the car off and on again i will some times lose the light for a few minutes and 4wd will work.
when the light turns on it will not turn off unless i stop the car and motor.
the light has come on every day for the past two weeks that i have been keeping track.
i have all the factory systems intact (4wd abs hicas) nothing has been removed.
abs and hicas work fine.
I am running an aem ems for my year gtr for my ecu



last but not least im currently running 470 whp at 20 psi and two wheel drive is a death trap with only a pair of 245 25 17 to keep me planted.


some one please help me!

ps feel free to call my cell at anytime to ask me for more details or to let me know what you think i might need to do. names dustin 604 786 1272


thanks

[skyline_steve]

Whats the tread like on the tires, i had a bunch of times where my tires were more worn out in the back and it caused this issue for me so i replaced the tires and the problem stopped.

[MarusGTR]

You could have a bad G sensor. Wouldn't stopping at a light make the system calibrate since it would be in neutral and stopped? Maybe something dosen't jive when the AWD checks wheel speed and the G sensors.

I'm just throwing this out there without knowing the mechatronics behind the GTR's AWD system. But it's the only thing you haven't checked.

[DBar]

yea as far as tred goes i think that the front and rears are fairly close to the same shape. the tries are pretty new. also it seems that if the 4wd light comes on its right after i hit the brakes.It does not come on every time i hit the brakes but when it does come on two things are for sure. one is the 4wd is locked out and will not come back till the light goes off. second thing is the light will not turn off unless i shut the car down and turn it back on again. i can check the g sensor but it will throw a faulty g sensor code usually if the sensor if messed up. any more ideas?

[DarkCaporaL]

Generally code 21 is TPS related, but you switched that out.
I'd double check to make sure you bled it correctly and that your reservoir is topped off. What kind of fluid did you use?

Did you try resetting the ATTESA ECU?

You're running an R32 right? (I think the codes are different from R32 to R33).

[DBar]

the system is bled. the fluid is exactly at the max line and i used dextron atf fluid. im not too sure what you mean by reseting the attesa computer. i have unpluged it and reinstalled it as well as i have removed the battery and reinstalled it.

on a side note the past week the light has come on only 3 times. all of which when i put on the brakes. At this point i am going to say that something is wrong with the wheel sensors. This is a possibly as they are the only ones that can be exposed to water and are involved when i put on the brakes. Im going to clean them all and see what happens. This conclusion does make sense right? im not just going crazy.. am I?


lol thanks for all the input.

[DarkCaporaL]

At this point you might as well check them. The logic is sound that it seems to relate to a wheel sensor if it only happens when you brake.

I would find it weird though that it would shoot you a code 21 (TPS fault) if it's a wheel sensor. There is a fault code associated for each individual wheel sensor which is not 21 lol.

Maybe there's a short somewhere messing with the atessa ecu's readings.

[DBar]

i know what you mean but i think i understand why the tps sensor code keeps poping up. when a sensor tweaks out or has a quick error the system checks to see what is out of spec. This is my theory anyway. when the system is checked my throttle will never be perfect. this is because i am running an aem ems as my ecu. not to say the ecu does not work for the car as it should, because it does. the reason i think the ecu is the reason for the tps code is because the ecu itself is flawed. the aem ems cannot understand 0% throttle. so even when my throttle is fully closed my ecu will still read 3% throttle. im sure this messes with the other computers in the car and when a sensor has a problem the car sees the throttle as the problem. so after cleaning the wheel sensors i have yet to have the 4wd light come on.

[DarkCaporaL]

Hopefully you'll never see that light again.

[DBar]

so far so good. In the end i think it was the wheel sensor. The abs ring on the right cv shaft suffered a rip in the boot once upon a time and the wheel bearing on that side was also dead. i think that the grease from the boot and or the wheel bearing caked the abs ring making the magnetic pulse to the sensor very weak and thus throw a code. All in all im glad its gone cuz 4wheel drifting in the rain is sooo much fun!

thanks for the input..

[MarusGTR]

Glad you got it fixed, didn't think about the ABS sensor

[skaG]

Dustin, so its been good so far, anyway one more thing to check about 4WD light. for next time you might want to check on the transfer control actuator?
good luck and keep me post on today's time(drag), hope it will be dry road !!
cheers,
Akira

[DBar]

thanks Akira. yea i went to mission again tonight and no such luck with the run. Im going to have to check out my tune tomorrow because even with the better spark when the car is hot and i try to boost it seems too rich and i misfire real bad. Oh the joys of trying to make power from an rb26 lol. I just hope that ill be able to get a good run in next week as its the last one of the season.

[skaG]

ok, under heavy boost have you play around the ignition timing? this might be a ticket for you,
good luck!!

[DBar]

hey yea i went to mission and the issues of the spark was present. the best i could do was a 13.1. i did all my system checks and all of it seemed fine. As of sunday i have rid myself of my ignition issue. Now i can full boost and hit redline. turns out the problem was the NEW set of plugs i put in. I have no idea whats wrong with the plugs but they just plain dont make a good spark i guess. I seemed to fix my misfire issue when i went back to my OLD plugs gapped to .028. so this is good news and with good news, bad news has to follow. I may have fixed my sparks but the 4wd light has come back from the dead. lol F#@%! MY LIFE...