RBX

I have searched and everyone seems to get the code 51 at some point and replaces the TPS, or finds it is just out of adjustment.
Getting a code 51...A/c issue OR TPS. TPS checks out, and it's less then a year old(new OEM part)
Trying to figure out what and where the 51 is coming from, the A/C wires seem to be in OK shape(corrosion).

Any ideas? My search never reviles anything about the A/C, just the TPS.

BTW, 88 4Runner 3vze

MudHippy

The A/T Neutral Start Switch(a.k.a. Park/Neutral Position Switch) circuit. Meaning, if you shift the automatic transmission into any position/gear besides "P" or "N" you will get code 51.

But you don't have an A/T do you?

RBX

HMMM, well i converted my Auto to a Manual, and perhaps something is a miss now. I never had the code before, and by before i mean when i did the tranny swap. I'll double check me wiring...thanks Mudhippy.

Also i meant to post that i am getting a crazy idle issue...only happens when the truck is at operating temperature and doesn't seem to happen everytime:
Drive truck, come to a stop(normal driving push the clutch in) and the rpm will rise to 2000rpm, if i blip the throttle she settles back down. I could drive and pull up to the next stop and the idle is fine...does't seem to be a pattern. And the rise in RPM to 2000rpm can be slow, meaning, as if i were trying to gradually raise the rpm with my foot on the pedal...any idea?

thanks again

Punchy

The 3vz auto ECU changes (retards) when going from park to revers and drive so it doesnt jerk the vehical.
Maybe this is a symptom.
The autotrans switch/wiring is seeing it in some other gear and the speedo signal is telling it otherwise and the ECU/ECT is throwing a code.

Cant see a error code 51 in my book for 3vze, But the 22RE "Displayed when IDL contact OFF or shift posision in R, D, 2 or 1 ranges with the check terminals E1 and TE1 connected.

RBX

Thanks, So are you saying that my ecu is retarding the spark all the time? I'll check to see how I can fake it out.

Thanks again guys

MudHippy

No no no...that's all wrong.

Let me try this again.

It's called the Neutral Start Switch(a.k.a. Park/Neutral Position Switch) circuit. Why is it called that, and what does it do?

The NSW circuit is a safety feature that prevents the engine from being STARTED(by interupting the STA/Starter Switch circuit) whenever the transmission is NOT IN PARK OR NEUTRAL. Hence the name NEUTRAL START SWITCH.

It has NOTHING to do with ignition timing.

To "fake it out", or get rid of it without swapping to a M/T ECU, you could try connecting the NSW pin on the ECU to the STA circuit. I would assume that if the NSW pin is connected to the STA circuit with the ignition switch in the ON positon, then the ECU thinks the neutral start switch is closed(in the ON position) with the transmission in "P" or "N", thus no code 51. BUT, I'm not even sure if there's any reason to do that much(even if you can). Meaning, I'm not convinced that doing so would make any difference in driveability(even if you could). How/why would it? Not to mention the fact that I can't even figure out how/why the truck would start at all if the NSW circuit were missing the NSW. Meaning, how does the engine start with the wrong ECU? Does it really? How? Why? And doesn't the fact that it starts mean it's not related to the NSW circuit? And what does the Starter Relay have to do with any of this?

Anyhow...


AFAIK the ONLY reasons for code 51 existing are:

• To tell you that the TPS is malfunctioning, and/or is misadjusted, and/or has a fault in its IDL circuit. Or that there is a problem with the accelerator pedal/cable causing it to appear as though there were a problem with the TPS.
  
• To tell you that the A/C switch is ON during Diagnostic Test Mode, when it shouldn't be, and/or that there's a fault in the A/C switch circuit.
  
• To tell you that there's a problem with the Neutral Start Switch, and/or the NSW circuit. Or that the transmission isn't in "P" or "N" during Diagnostic Test Mode, causing it to appear as if there were a problem with the NSW.
  
• To tell you that, after all of the above possibilities have been eliminated, the ECU itself is faulty.

And...if you're still interested in messing with it here's the 88 3VZ-E ECU pinout. The pin directly to the right of the STJ pin should be the NSW pin(this is obviously a M/T ECU...but close enough).


EDIT: I've confirmed via the 88 3VZ-E wiring diagram that the ECU pin next to the STJ pin(U Connector #2 pin) is in fact the NSW pin(U Connector #1 pin).

So...are you really using an ECU for an automatic with a manual? Because I'm totally confused at this point. What the hell am I even talking about?

RBX

Mudhippy,
I am using the original A/T ECU without the ECT, and previously had no codes.
The rig fires up as you would expect any Toyota, i experience no stumbling under acceleration, no missing.
I'll have to go back thru my swap thread to see how i handled the NSW.

My A/C seems to run fine, but i think the issue is in that circuitry. I've checked my VSV and it passes when diagnosed with the multimeter, however i cannot get the idle up valve to work, and i forgot to check it the other day with the multimeter.

thanks

ToyoTech559

so your using an AUTO ecu with a Manual transmission?

RBX

Yep.
I read tons of threads all over the interwebs with guys that did the same swap, the ECT just piggy backs the ECU.

MudHippy

Well...I still can't figure out how you managed to make that work. But I think I'm seeing the picture well enough to understand that you should have had to do something with the NSW circuit to aviod getting code 51. Like adding a Starter Relay to the STA circuit, and/or in some way connecting the NSW pin on the ECU(U Connector Pin #1) to it.

That's what it looks like from here anyway...

ChefYota4x4

iTrader: (5)

Watching.... Best wishes on this one, RB

RBX

From my build thread: