Troubleshooting fried ECU components
I fix a ton of ECUs, the 3 most common problems are the caps, the solenoid/actuator drivers, and the sensor ground trace on the back of the PCB(in that order).This apllies to NT ECUs as well.
There is plenty of info around the net on the caps, I've noticed there is a small surface mount decoupling cap(C14-removed and circled in the pic) that is usually bad as well, and most info doesn't say anything about this cap.I usually just replace it with a non-surface mount .1 ceramic cap closer the the connector(also circled in the pic)
The drivers fry due to excessive current, usually from wiring problems(shorts,etc) or faulty actuators/solenoids.Swapping ECUs in most cases will just damage the new ECU.If these are damaged inside your ECU, check the actuators/solenoids and their wiring BEFORE you swap ECUs.These are common in all 1g ECUs(T and NT), they can be replaced, without replacing the whole ECU.Note problems with the drivers usually lead to problems with the sensor ground trace(below).
These are M5269L low saturation output drivers labeled IC104-IC109:
IC104 is MAF active reset filter(turbo only)
IC105 is ISC coils B1 and B2
IC106 is Wastegate 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
Finally, the sensor ground trace.If you are getting a CEL, and the codes are sensor related but the sensors are OK, this is usually the problem.You can test this by checking for continuity between the main ground and sensor ground pins on the ECU.If there is no continuity, check the back of the ECUs PCB for a fried/broken trace.I don't have pics of this, but it should be fairly easy to spot.After checking for shorts to the sensor ground under the hood(and fixing above problems), you can just solder a jumper to restore the connection.
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