HAWAIIANSTYLE

(94 4runner v6).. jumpered t1 and e1 and got a code 12 (knock control sensor signal/rpm signal)... could this be a symptom of why i have lack of power and poor mileage. afterall, i've already tried narrowing down my first to do list,.. blew the gaskets earlier this year and had everything rebuilt. spark plugs and wires, dist. cap n rotor, fuel filter, fuel pump, vacuum leaks, compression, timing, injectors, seafoam, cat, o2 sensor,.. all changed. oops, i overlooked changing the knock sensor pigtail when doing the headgaskets. does this mean i have to do the timing all over again after i change it out?...

125rmodel

I have the same problem with my 93. did you ever get it solved

MudHippy

O.k., the first thing that needs cleared up, before we can get you started on this, is clarification on the true description of the code.

Code 12 is an RPM signal related code. It has nothing to do with the knock sensor.

FSM page EG2-176 from the link below describes the nature of the trouble as being "No G or NE signal is input to the ECM for 2 sec or more after starter turns 4N." Which in laymans terms means that the ignition return signal to the ECM, which it uses to calculate engine rpm, is shorted somewhere between the distributor and the ECM.
http://personal.utulsa.edu/~nathan-b...85diagnosi.pdf

The ECM pin out locations of the G and NE signals, and their respective resistance values(hot and cold), can be found on page EG2-256.
http://personal.utulsa.edu/~nathan-b...e/102engin.pdf

But as is also described on page EG2-176 of the FSM(from the first link provided above)it can also mean there's a short somewhere in the STA(starter signal)circuit between the battery and the ECM. To troubleshoot the STA circuit follow the instructions given on page EG2-193 from the link below. The ECM pin out location and voltage specifications for the STA circuit can also be found on page EG2-255 in the link directly above.
http://personal.utulsa.edu/~nathan-b...86troubles.pdf

If all checks out with those two circuits, then the ECM itself could be faulty.

The entire FSM can be accessed from the link below.
http://personal.utulsa.edu/~nathan-buchanan/93fsm/

Fair warning, I have no clue what would be causing the issue. But I can point you in the right direction, hopefully. Any more help from me on it is by no means guaranteed. I've never heard of anyone having this code come up untill today, let alone have any specific details on how to resolve it. I'll try and do what I can though.

Good luck!

125rmodel

humm good info im going to look at this stuff in the morning

125rmodel

everything checks out with the wiring and distributor and starter. I also replaced the ignitor, knock sensor and wiring, coil, tune up stuff, and the distributor still same code 12. Also food for thought when i reset the computer it will flash that there is no codes until i try and crank it up then light comes on immediately and it will start and run ok after the third or fourth time trying to start it. but it will never start the first time, like it has to go into a limp home mode to start and run

sb5walker

The G & Ne signals are not "ignition return", they're the rpm signals from the distributor's signal coils. It sounds like you may have already checked the resistance and air gaps of those, but if not, the specs are here:
http://personal.utulsa.edu/~nathan-b...12onvehicl.pdf

(The "ignition return" signal is the IGF, which goes from the igniter back to the ecu. It provides confirmation to the ecu of the spark. If there is no IGF signal, the ecu will stop firing the injectors. But you would get a code 14 if the ecu were complaining about that.) On 3vze vehicles, the signal coils connect directly to the ecu as Mudhippy mentioned, but on 22re trucks there's only one signal coil and it connects to the igniter, and from there the signal is passed to the ecu.)

If the signal coil resistances and air gaps are okay, check the wiring between the distrib and ecu, and the ecu grounds. For the grounds, verify almost no ohms between ecu term E1 and a good chassis ground, between E01/E02 and the engine block & head, and between chassis and neg batt post and engine and neg batt post. I think the ignition system uses the E1 ground, and it happens that there's an E1 terminal in the check connector, so very easy to check ohms between that and the neg batt post. If more than, say, about 3 ohms, I would clean up the ecu terminal E1 ground point (which is supposed to be on the driver side post) and also clean up the battery cables and posts.

125rmodel

I have replaced the wires between the dist and the ecu since they were in that shielding jacket and to be positive there was no problems with it even though they ohmed out good i replaced that part of the harness with some new stuff i got from aircraft spruce and specialty. I went throught the FSM basic voltage checks and will go back and recheck the connections and such you mentioned and get back with you. Everything seems to check out good so I am starting to think I may actually have a bad ecu, but thats not the normal case so an ecu will def be the last ditch effort.

MudHippy

O.k., yeah that sounds right. Sorry for the confusion. I'm still trying to wrap my head around it. But that makes a bit more sense, I guess. When I said I didn't have a clue as to what would be causing the issue, that was no understatement.

I gave it my best shot though. Kinda figured it couldn't hurt too much to. The poor OP never even got a reply at all. I was worried nobody was gonna bother even trying to help this guy either.

Thanks for jumping on board to lend a helping hand, and straightening out the misunderstanding!

125rmodel

thanks for the feedback anyways i am stumped too ha ha but i think i will try an ecu they run about $250, I have made worse investments

sb5walker

If not the wiring, grounds or ecu, it may be the distributor. My veezy had a persistent pinging problem for many years; checked everything I could think of including the signal coils and could never solve the problem. Then a few years ago I replaced the distributor because the bearings were going bad & squealed terribly when very cold. With the new distrib, the pinging issue completely disappeared. Probably the G or Ne signals were not being generated properly, even tho the resistance of the coils checked out. My best guess is that the bad bearings caused the shaft to move around enough to mess up the rpm signals. You might try wiggling the shaft side-to-side - there should be no movement.

MudHippy, thanks for the - glad to help when I can.

125rmodel

my old dist checked out fine and i bought a reman unit and it did not make a difference :-( it passed the FSM checks and I did it anyways with no luck

sb5walker

Oh well, just a thought. Good luck with it.

93YotaGuy

Any luck figuring this out? I'm having the same problem with my truck and am stumped.

125rmodel

I finally figured out that the distributor connector had been replaced before I bought it and the dummy that replaced it put the wires back in the connector in the wrong order. Also im not sure if I mentioned that I bought my truck running like that. 93yotaguy what have you tried on yours?

93YotaGuy

https://www.yotatech.com/forums/f199/back-grave-231390/

93YotaGuy

Well my code 12 turned into a code 13. I ended up finding that the wires that went from the igniter to the alternator had burned up somehow. I replaced the harness and the code went away.

ToyotaViejo

Hate to be a pain, but I'm wondering if you might snap a pic of the ignitor and wires you fiddled with to fix the problem?

93YotaGuy

Maybe you should look at my above post and click the link that explains it all