Does resetting the ECU frequently cause any probs. My truck seems to run so much better after I clear all codes. My truck had a miss at 30mph, I had a overboost code and when I cleared it and every thing is running much smoother, no miss for now anyway.

 

I've reset mine tons of times without incident. Do the codes come back? might be time to dig into it to figure out what's going on.

 

i have been wondering about this. how exactly do you reset it?

 

Pull the EFI fuse for a minute or so to reset the computer. The only change other than clearing codes is that the mixture calibration for open loop (warm up and full throttle) will reset to neutral. There are two settings more lean and two more rich, based I guess on O2 sensor readings while in closed loop. Won't hurt anything to reset the ecu.

I don't think the open loop mixture calibration will affect normal closed loop mixture calibration which is based on O2 sensor readings, but it will affect how the motor runs while warming up. The ecu will probably recalibrate to where it was before in just a few trips.

 

oh ok. thank you

 

I have a 3vze '89 runner, I have replaced the KS and pigtail, PCV, gaskets, hoses, O2 sensor, shift solenoids, trans filter, PS pump, and all of the nasty fluids assosciated, and corrected the timing. My runner runs much better then when I bought it a month ago but I still can't clear the CEL (taunting me with code 52). The battery has not only been unplugged, but removed in order to gain better access to the PS pump. I tried to locate the EFI fuse in the ECU but it just doesn't look the same as in the manual, and quite frankly I'm not certain the thing hasn't been tampered with by the last owner. I pulled what I thought was the correct one to no avail. Can somebody please show me with a pic, which fuse I am to pull? I've done all of these fixes in order to clear that code and I have yet to get this thing in my name because I know it won't smog if that stupid CEL will show its ugly little face while on the DYNO. On that note...Is it normal for the CEL to go away when the engine turns off and re-appear once warmed up?

Danielle

 

I just had a similar problem with my 91 3vze. Replaced knock sensor, pigtail, and then all wiring back to ecu. I used the original wire from the wiring harness to connect my new shielded wire to the ecu.

I was still getting error code 52. I then de-pinned the knock sensor wire from the ecu plug/connector and checked to see if the wire was landing on the pin inside the ecu body. Sure enough, the wire connection was loose/not great on the ecu pin.

I went to a salvage yard and found a donor vehicle and got a “new” used ecu plug with all the wires attached. Chopped the plug with about 4” of wire sticking out if it. I then de-pinned the knock sensor wire from the plug and replaced my bad knock sensor wire end with the new wire end (soldered it on), shoved the new wire end into the ecu plug and put the plug back into the ecu. Fired up the engine and the code 52 was gone finally!

moral of the story - de-pin the knock sensor wire from your plug connector and check to see if the wire is making a good connection to the ecu pin. De-pinning requires a special tool available at Napa and a special skill I learned from watching a few YouTube videos on how to de-pin a Toyota ecu plug. But this was the only connection I hadn’t replaced, and it was the fix for my knock sensor code 52.

 

Poor connections at plugs are often over looked because so many times when back probing with the meter lead the probe will complete the circuit and you call it good and move on.

Bent pins are another good one vehicles getting old wires get brittle from the thermal cycling the conductor breaks insulation stays intact.

I had a good one wire would ring out but would not carry the load turns out all but one strand of wire was broken discovered when autopsy was done on the wire.