Very strange "normal" code 51

[rtrdpenguin]

I'm having a really weird problem that just started yesterday when I took the Supra out for a quick spin with the exhaust silencer in to see if that helped my overboosting problem (thanks everyone who's been helping me with that!)

Whenever I push the gas/open the throttle, my check engine light comes on. When in diagnostic mode, the CEL blinks steadily (the no code blink) and reads a code 51 when I open the throttle, which should be normal right? The CEL stays off when the throttle is closed whether I'm in diagnostic mode or not.

My question is, why is the CEL registering a code 51 when it's not in diagnostic mode? I'm relatively sure it's normal for it to give a code 51 in diagnostic mode when the throttle is not closed, since that's what 51 means. But it also gives me the code when not in diagnostic mode...

 

[IwantMKIII]

if you do not have the terminals jumped, and the check engine light is flashing, then something else must be tripping the system into that mode. 51 is normal in diag mode when on the throttle only as its a real time code

 

[rtrdpenguin]

That's what I thought, but when I check codes after it comes on all it does is blink the "no code" rapid flash.

 

[IwantMKIII]

^that would be a good thing

 

[rtrdpenguin]

Yes, but the light still comes on whenever the throttle is pressed after I check codes and remove the jumper from the diag box.

 

[IwantMKIII]

^does the light stay constant or does it flash?

 

[jetjock]

^ From what he wrote the light flashes.

OP: Instead of a jumper put a voltmeter across T and E1 in the diag block. Tell us what it reads. Or check ignition timing at hot idle. Or check Vf both at idle and off idle.

Any of these tests will confirm whether the ECU is in diag mode (which it appears to be) with the jumper not in. The first test is quickest but not the best.

 

[IwantMKIII]

^would it be a short that causes this? or is there actually a trip that will cause it to go into diag mode?

 

[rtrdpenguin]

Thanks JJ, I'll go dig up my dad's ancient multimeter. I think I set my timing when the engine was relatively cold too, I'll go look at it when it's hot.

 

[NashMan]

ant that have to do with ac switch or is that 41 don't remmber and to lazy to look it up