ECU / ECM Reprogramming - Misfire Problems (1 Viewer)

[jgray]

Long time 100 owner here chasing crazy misfire problems that are absolutely killing me!

I am throwing misfire codes on cylinders 2,4,6,8 and have not been able to figure out why. I've verified good compression, all coil packs are good, spark plugs, timing, valves, cams are in proper positions, cats are good, injectors etc. Seems to me that only a few things could affect all four cylinders on the same side of the engine. I've checked almost everything I can think of and things seem to be pointing to a possible electrical problem.

Question: Has anyone successfully swapped their computer, ECM or ECU - whatever you want to call it? I can find plenty of early 99 (split year ECU apparently) ECU's available. My question is if I get another will it work or how difficult is reprogramming? Will I need new keys? (I have both of mine still)

Any help would be greatly appreciated! My 100 hasn't been running right for months, I miss it and no one seems to be able to figure out what is wrong. I know a lot about these trucks and have been on this forum for almost 10 years. Not much is turning up in my searches. Please chime in with suggestions if you have any advice!

 

[Trunk Monkey]

I had a cruise control issue a few years ago that one of the possible solutions was to replace the ECU. Friend of mine with a same year tried swapping his in and even using TechStream it wouldn't work (he works for Toyota training). I finally had it replaced at the dealership using the one time "I lost all my keys" clause. Toyota will replace the ECU once for free for vehicles that have hard coded keys, it was only a couple of years that have that issue. You have to buy the new keys.