View Full Version : Testing an ECU

12-09-2004, 01:45 PM
I am wondering how you can check an ECU to see how it is functioning. Like if it is running the way it is supposed to? Any ideas are appreciated.

12-10-2004, 05:07 AM
There are a few things you can do to try to test the ECU short of reverse engineering it. You can run thorough all the I/O pins to conform that they are all ok in regards to sensors. You can take it out of the case and inspect the circuit board for burnt traces if there is a drastic problem with it. I have actually successfully reaired a ECU by repairing the burnt traces. But without knowing what kind of problem your having I'm shooting in the dark. The absolute easiest way to test ECU's are just to swap in a known good one and see how the car runs. What's wrong with your car?

12-10-2004, 01:19 PM
it will not rev over 4500 rpm. Like it hits a rev limiter.Original thread (http://www.celicatech.com/forums/showthread.php?t=208) I am thinking it may be the afm but I am not sure. I think I will just unplug the afm and see how it runs. If it runs worse then I will get a new afm if not then I think I may have to find a new ecu. Dr. Auto this is for a 4age 20valve not our typical 4age found in corollas. Because of the VVT i can not use any other ecu. Any advice?

12-11-2004, 07:27 AM
check your O2 sensor.
did you try resetting the ecu?

12-15-2004, 05:39 AM
Well first, An O2 sensor will never cause drivability concern in a specific RPM range. The ECU is mapped for open loop operation if there is a big problem with the o2 (which it does anyways on startup).
I would first suspect the air flow meter(AFM/MAF) and/or manifold absolute pressure sensor(MAP). Second a TPS.
I would confirm cam timing, ignition timing. Visually inspect ignition components ect ect....and just do a basic non-caring inspection of the engine bay. Something might just jump at you if you just medatate, sitting on your special carpet in the engine bay.
Something to ponder..... try disconnecting the VVT solenoids and see how it runs. This will render the VVT inop, and you can diag accordingly if somthing shows up. I am not very familular with the 20v, but if I remember it has the quad Throttle body setup correct? Does it have the variable intake runner setup thats not working correctly? I don't think the 20v has that but who knows.
And if you really want to you can make a 4A-GE ECU work on it. Obviousely you will not have VVT if you do that, and you'll have to screw a bit with a little bit of the wiring. But for testing purposes you can do it.

12-20-2004, 04:20 AM
Hmmm, the general rule is that Toyota ECU's don't go bad, however i guess you never know. Are you absolutely sure that the ECU is the same year as the engine? This gave me a problem for a while with my 3S-GTE swap. I do remember some people having a 4500rpm fuel cut issue when swapping 3S-GTE's into their cars, but i don't remember what caused it, or fixed it. Oh, yeah, if you want help with it sometime, let me know, i'd love to see a 4A-GE setup in a Celica.