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.

What would cause this (PCM failure):

IMG_20101204_152154.jpg


This doesn't look like the typical failure-mode for these PCMs, any idea what would cause this? I think it's something related to the injector drivers since they weren't pulsing and we found the PCM like this while diagnosing.

Thanks,
TJ
 

donkeylips

Well-known member
Joined
Jun 18, 2009
Messages
552
Location
Rochester, NY
I'm no ecu expert but it looks like your ISC motor is shorted and took out your ISC drivers. I've had this happen a few times, and it's a common way that something wrong with your car can take out an ecu. I'm actually about to buy an eprom that has sustained this damage but still works fine with no ISC. Your FSM will tell you which pins to use to check the resistance of the ISC coils.
 

So I'm a domestic gear-head at heart (600RWHP NA C5 Z05 track car) and don't know what "ISC" is. /ubbthreads/images/graemlins/frown.gif

Thanks,
TJ
 

Terry Posten

Well-known member
Joined
Dec 16, 2003
Messages
9,009
Location
Davenport, Iowa USA
Idle Speed Controller. It is a small motor that is mounted under the Throttle body inlet that has a 6 prong square plug.

Here is a pic that should help you test your unit. If it is bad, you DO NOT want to plug in a new ECU (Engine Control Unit), what you are calling a PCM, without leaving the ISC unplugged until you get a good one.




You should have around 30 ohms of resistance on each coil. An open coil is bad but will not hurt the ESC. A shorted coil is bad and will hurt the ECU.
 

Thanks Terry... I guess I need the testing specs for the ISC... and probably a new ISC too. Yay.

-TJ
 

jepherz

Staff member
Joined
Aug 8, 2004
Messages
7,877
Location
KC, Missouri
I think the specs are on VFAQ, although all you need to do is check the resistance of each of the 4 coils in the picture above. They should be all around 25-30 ohms, give or take. It's obvious that one of yours is going to read close to 0 ohms.
 

holeshotmoe

Well-known member
Joined
Apr 7, 2005
Messages
1,291
Location
MD
Found this on DSMTALK:
IC104 is MAF reset (turbo only)
IC105 is ISC coils B1 and B2
IC106 is Boost Control and Fuel Pressure solenoids(turbo only)
IC107 is ISC coils A1 and A2
IC108 is Purge and EGR solenoids
IC109 is A/C and Fuel pump relays
...and the following in THIS THREAD here:
Just for future reference on turbo ECUs:

M5269L low saturation output drivers labeled IC104-IC109:

IC104 is MAF active reset filter (pin 1) (turbo only)
IC105 is ISC coils B1 (pin 7) and B2 (pin 1)
IC106 is Wastegate (pin 1) and Fuel pressure solenoids (pin 7) (turbo only)
IC107 is ISC coils A1 (pin 1) and A2 (pin 7)
IC108 is Purge (pin 1) and EGR solenoids (pin 7)
IC109 is A/C (pin 1) and Fuel pump relays (pin 7)

The pins are the outputs the M5269L driver, matching inputs are 3 and 6

So it does look like IC105 cooked due to a shorted ISC. Had this same issue on one of mine. Also, your picture seems to indicate possible damage to some of the other traces on the board. There's a few guys here that do repairs, and a few may have a spare IC. I've heard of someone salvaging IC108 because they had removed the smog control components from their car, since it wasn't being used. But you had better check with some of the guys that fix these things (e.g., keydiver) first. But if you get one of the chips, a tv repair (are there still such businesses?) shop should be able to solder it in for you, and should be able to repair any broken runs on the board.
 
Support Vendors who Support the GVR-4 Community
Boosted Fabrication ECM Tuning ExtremePSI Fuel Injector Clinic Jacks Transmissions JNZ Tuning Kiggly Racing Morrison Fabrications RixRacing RockAuto RTM Racing STM Tuned

Recent Forum Posts

Top