Originally Posted by CharlieHustle

Updating this thread in the event others encounter a similar issue of their own. I've finally managed to rid my 4runner of the CEL code 12. The culprit was the one piece I hesitated to replace because it tested out fine on a multimeter: the distributor.

2 years ago, I went to the junkyard to pick up a replacement distributor and swapped the original one out. After clearing the ECU, I start the engine only to still have an illuminated CEL. Checked the codes again and still a code 12. Tested the distributor according to the procedure in the service manual and everything checked out fine. At that point, I ruled it out from being the problem.

Time passes and registration on the vehicle needs updating, but not without passing a smog check. After changing out the ignitor, coil, cap, rotor, and ecu, the CEL still remained on. Removed the loom around the engine harness to inspect the wiring and found nothing. As a last ditch effort, I pick up another distributor at the junkyard and swapped it in. Problem finally solved.

Resistance and air gaps on all three distributors measured well within the allowed specs. The car never had an issue starting or producing spark. I assume the electronics within the distributor itself were to blame.

Originally Posted by Edionne13

I've replaced rotor an cap, spark plugs wires Ngk. Spark plugs are fine, ignotion control unit new. Used ecu thinkino that was bad. You replaced the entire unit? I have a 93 engine went bad swapped over the top half of engine. From 91 to my 93 3.0. I have the Distributer from the 91 just different connections is why I didn't use it. May have to try it.

Originally Posted by Terrys87

I have seen two trucks with computer issues. The only way that a friend and me was able to find out the computer was at fault was just by swapping them out. I have a spare computer in storage and it says it is remanufactured or rebuilt on the cover of it. They do fail every once in a while.