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Blown ISC Driver

Sometimes a bad ISC (idle stepper control) motor can damage the driver chip inside the ECU. Here's what to look for to identify this situation.


There are two things I'd like to note here. First, when these blow, they often take out tracks underneath the driver. In these cases, simply replacing the driver is ineffective. So if you remove this yourself, look carefully around the board to make sure no tracks were damaged when the driver blew.

Second, these blow for a reason. If you simply replace one with another one without being certain you have addressed the underlying cause (typically a bad ISC motor), the new one will simply blow again when the ECU is powered up.


These drivers are Mitsubishi M5269Ls and can not be easily sourced. They can, however, be shared (swapped, donated, pulled, etc.) across various Mitsubishi ECUs.

2G PARTS ('95 ECU)

  • IC111 not populated
  • IC112 controls ECU pin 3, Fuel Pressure Solenoid (FPS), and ECU pin 11, Boost Control Solenoid (BCS).
  • IC109 controls ECU pin 8, Fuel Pump Relay, and ECU pin 9, Evap Purge Solenoid.
  • IC108 controls ECU pin 6, EGR Solenoid, and ECU pin 20, Fan Motor Relay (High).
  • IC106 controls ECU pins 5 and 18, Idle Speed Control (ISC) Servo (coil pair A).
  • IC107 controls ECU pins 4 and 17, ISC Servo (coil pair B).

1G PARTS ('90-'94 ECUs)

  • IC104 controls ECU pin 14 ('90) or 6 ('91+), MAF Reset signal. The other half of the chip is unused on US DSMs.
  • IC105 controls ECU pins 67 and 68, Idle Speed Control (ISC) Servo (coil pair B).
  • IC106 controls ECU pin 57, Fuel Pressure Solenoid (FPS), and ECU pin 105, Boost Control Solenoid (BCS).
  • IC107 controls ECU pins 58 and 59, ISC Servo (coil pair A).
  • IC108 controls ECU pin 53, EGR Solenoid, and ECU pin 62, Evap Purge Solenoid.
  • IC109 controls ECU pin 56, Fuel Pump Relay, and ECU pin 65 Air Conditioner Compressor Clutch Relay.
driver01.txt · Last modified: 2011/06/07 06:41 by twdorris