I don't like disconnecting the battery all the time because I hate resetting my stereo presets and dash clock. Is there harm in just unplugging the ecu? I wouldn't think so but I tend to make assumptions that bite me in the ass later.
The Top Mitsubishi Galant VR-4 Resource
Join the best E39A 1991-1992 Mitsubishi Galant VR-4 community and document your GVR4 journey.
- Software Upgraded - Reset Your Password to Login
In order to log in after the forum software change, you need to reset your password. If you don't have access to the email address you used to register your GVR4.org account, you won't be able to reset your password. In that case, follow the instructions here to regain access to the forum.
twonineseven
Well-known member
I swapped out ECU's today and nothing reset, but it was only a couple secs I think it has to be unplugged for like 5 mins and then it resets. But i've had my old vr4 in the shop b4 with out the ecu plugged in without any harm being done to it (or so i thought)
Terry Posten
Well-known member
There is nothing wrong with unplugging the ECU. Makes for a good "kill switch" if your going to be storing the car for a long period of time.
You really only need to unplug the smallest, 10-pin connector to reset the ECU. All the power connections are on those 10 pins. Within 10-15 seconds the capacitor will usually drain, and you will lose the fueltrims and other stored settings.
IIRC, I think you can also pull the dome light fuse, with the car shut down, and that will also remove the battery backup to the ECU.
IIRC, I think you can also pull the dome light fuse, with the car shut down, and that will also remove the battery backup to the ECU.
Thanks guys.
OMFGeofffff
Well-known member
Should I have left my ecu disconnected for a little bit before swapping in a new one?
Quoting keydiver:
You really only need to unplug the smallest, 10-pin connector to reset the ECU. All the power connections are on those 10 pins. Within 10-15 seconds the capacitor will usually drain, and you will lose the fueltrims and other stored settings.
IIRC, I think you can also pull the dome light fuse, with the car shut down, and that will also remove the battery backup to the ECU.
Jeff does the 91-94 ecu's use those capacitors also if not how do you reset those sorry for the thread jack.
You really only need to unplug the smallest, 10-pin connector to reset the ECU. All the power connections are on those 10 pins. Within 10-15 seconds the capacitor will usually drain, and you will lose the fueltrims and other stored settings.
IIRC, I think you can also pull the dome light fuse, with the car shut down, and that will also remove the battery backup to the ECU.
Jeff does the 91-94 ecu's use those capacitors also if not how do you reset those sorry for the thread jack.
stevep
Well-known member
The caps will discharge pretty much as soon as you disconnect the power.
Yes, this applies to all the ECUs.
Yes, this applies to all the ECUs.
Thanks steve
Quoting keydiver:
You really only need to unplug the smallest, 10-pin connector to reset the ECU. All the power connections are on those 10 pins. Within 10-15 seconds the capacitor will usually drain, and you will lose the fueltrims and other stored settings.
IIRC, I think you can also pull the dome light fuse, with the car shut down, and that will also remove the battery backup to the ECU.
Jeff I checked both in the engine and under the dash fuse boxes and I couldnt find a dome light fuse. Am I blind(lol) or is it hidden somewhere else or labeled as something else.
Thanks
You really only need to unplug the smallest, 10-pin connector to reset the ECU. All the power connections are on those 10 pins. Within 10-15 seconds the capacitor will usually drain, and you will lose the fueltrims and other stored settings.
IIRC, I think you can also pull the dome light fuse, with the car shut down, and that will also remove the battery backup to the ECU.
Jeff I checked both in the engine and under the dash fuse boxes and I couldnt find a dome light fuse. Am I blind(lol) or is it hidden somewhere else or labeled as something else.
Thanks
toybreaker
iconoclast
- Joined
- Apr 30, 2006
- Messages
- 3,581
It's the ten amp red fuse in position #17 of the fuse box located by the drivers left knee.
I *believe* it's labeled "room", but it's been awhile since I was in a vr4 fusebox.
If the clock loses it's time setting, you found the right one.
Quoting galant1517:
I don't like disconnecting the battery all the time because I hate resetting my stereo presets and dash clock. Is there harm in just unplugging the ecu? I wouldn't think so but I tend to make assumptions that bite me in the ass later.
ooops... /ubbthreads/images/graemlins/rofl.gif
I *believe* it's labeled "room", but it's been awhile since I was in a vr4 fusebox.
If the clock loses it's time setting, you found the right one.
Quoting galant1517:
I don't like disconnecting the battery all the time because I hate resetting my stereo presets and dash clock. Is there harm in just unplugging the ecu? I wouldn't think so but I tend to make assumptions that bite me in the ass later.
ooops... /ubbthreads/images/graemlins/rofl.gif
Last edited:
Ok thanks I will give it a try
So unplugged the number 17 fuse dome light radio etc the fuel trims went back to 100% low, med and high. Took the car for a rip HT are now at 98% Med trim is at 90% and low trim is at 82% again. Guess I will have to play with the fuel pressure to fix the high trim and the mas screw to bring the low trims up or am I missing something here. The car pulls hard but I seem to get anywhere from 1-12 counts of knock before only 1-6 at wot in 5th gear. Fuel pressure is currently set at 37 psi but like Jeff said the bitch could be off so I will lower it some more.
