aother code 51 thread

[WonIt]

So here is the deal. Car is a 1989 toyota supra with 7mgte,was auto converted to 5speed.

Recently replced the engine,which ran fine before I pulled it out of the donor car. Now its in and running.just getting the dreaded knock sensor code and code 51... after reading numerous threads. I have came to the conclusion that my tps is not bad.

I wired in my safc neo,it is showing 0v when not pressing the gas pedal,and voltage goes up when you press it.

While reading a fewposts today,I came accross one that said the knock sensor could cause the 51 code to pop up. I know that one of my knock sensors need to be rewired..

I am getting some bucking when accelerating,def. Not at full power... I know I am missing something from my post. Will be adding stuff as I remember.

 

[WonIt]

Any help would be appreciated

 

[jetjock]

Listen to this guy. I know him:

http://www.supramania.com/forums/showthread.php?46793-Code-51

Knock sensor problems (code 52) can't cause a 51 and your Neo doesn't display the signal associated with it...

 

[TweeT91109]

Listen to this guy. I know him:

http://www.supramania.com/forums/showthread.php?46793-Code-51

Knock sensor problems (code 52) can't cause a 51 and your Neo doesn't display the signal associated with it...

^^^^Smartass

And I love it.

 

[WonIt]

i will be following your guide tomorrow. will let you know what comes of it. thanks for the link.

 

[WonIt]

ok,i just checked the TPS by jumping the bottom 2 pins on the tps connector. 51 DID NOT dissapear. my next question is does the wiring for the TPS go from the connector strait to the ecu,or does it stop off somewhere else before landing at the ecu?

i am trying to figure out if there is any wires,or grounds that i may have overlooked somehow when installing the harness. the harness as a whole was in pretty good shape when i got it,not saying that nothing could be wrong under the surface.

 

[jetjock]

It does. All important EFI wiring goes directly to the ECU for reliability reasons.

http://www.cygnusx1.net/Supra/Library/TEWD/MK3/manual.aspx?S=Main&P=48

Check the continuity of that yellow/green wire. Better still (and a lot easier) measure the voltage on it at the TPS connector with the key on. If the wire has integrity there'll be voltage on it put there by the ECU. Check the ground on the other pin using continuity to battery negative. If both those check out either your jumper wasn't making contact, the code is not TPS related, or I f'ed up and got the pins wrong because, well, my eyes ain't what they used to be.

And be sure the AC is off and the car is in P or N if an automatic...

 

[WonIt]

I will do that tomorrow after work. Now I do not have my manual trans wired in at all,it was like that the before I swapped this engine in. Could that be my problem? Ecu is getting no signal from trans?

 

[jetjock]

One of the inputs that can cause 51 is the neutral safety switch. Do you have still have the auto ECU in the car? Did the code show up after you swapped in the 5 speed? If so that could be it. You can't just jump the connector where the switch used to be or you'll lose cruise control because when set the cruise system doesn't like thinking the car is in P or N. Has to do with over revving the engine.

 

[WonIt]

Yes,I am still using an auto harness and ecu. I did not have this problem when the last engine/5spd trans was in the car. Just had a flashing auto trans light. No cel or loss of any power...

tho I do think I had one connector from the 5spd trans plugged into the auto harness. I am also getting a speed sensor code. The plug from the trans side is a 2x2 plug I want to say. But I do not know which wires I need to splice to on the engine harness side. 2 of the auto plugs have been cut.

I will slide under there and take a look at it this afternoon... in the meantime,if anyone just happens to know the connector I am talking about ,and could help me out with the wire colors that I need to splice them on the engine harness side that would be great.

 

[3p141592654]

ECU Speed sensor is in the dash connected to the speedo cable (pink wire). The rear ABS speed sensor is the only one in the tranny.

Having dug through the ECU code, I can tell you that having the NSW permanently jumpered on will results in non-optimal ECU operation.

 

[WonIt]

It is prbably the rear abs speed sensor then,the abs light is on also.. gonna try and match the wires here in about 2 hours.

 

[WonIt]

Ok,so i finally got around to sliding under the car to try and wire in the speed sensor from my manual trans to my auto harness. was just looking to see if i could match the colors of the wires to any of the auto harness plug wires. from what i could see,none of them matched.

the r154 has 1 plug coming from it that i could see. 3 wires red,white,black if i remeber correctly. anyone know what color the wires should be coming from the engine harness? it is a 89' auto 7mgte harness. i am pretty sure this should be to the speed sensor on the trans

i could not seem to find the connector or wire colors using the tewd. if anyone could ring in on this,that would be great,that way i can slide back under there tomorrow before class starts and get this thing wired in to see if that helps with my problem. thanks for any info that might pop up.

 

[IwantMKIII]

I wired in my safc neo,it is showing 0v when not pressing the gas pedal,and voltage goes up when you press it.
.

I would like to point this big factor out before you dive ever deeper. Just because it's at 0V and it goes up, does it mean 51 will not be there. If i'm not mistaken, the ECU will accept a closed throttle position to be considered between 0-1V (I'm sure I will be readily corrected on this by JJ or someone if I'm wrong). Either way, code 51 is highly sensitive to the position of the TPS.

Example:

I use SAFCII. When reading the volts and trying to get rid of 51, my voltage (iirc) was .446 v. I adjusted the TPS to .535 v, still 51. Nudged it more up to .555V and no more 51, problem solved.

Remember, 51 is real time, so with the aid of safc and assuming the TPS is good you can jump the terminals for checking codes and slowly adjust the TPS until its gone.

 

[jetjock]

^

...your Neo doesn't display the signal associated with it...

As I understand it these controllers only display VTA. When associated with the TPS 51 is IDL related. VTA is only relevant to code 41 although there is one cause of 41 that can involve IDL.

 

[WonIt]

Yes,Ihave tried jumping the pins on the tps connector and the code still did not go away,so I am wanting to connect the rear speed sensor to see if that clears it up. Engine ran completly fine when I pulled it from the donor vehicle with no chicken lights or anythin of the sort. Still looking for the wiring on the engine side of the harness to figure out how to wire in the rear speed sensor.

 

[jetjock]

Connect the rear speed sensor to clear up a code 51? Are you serious?

 

[WonIt]

I missread something you wrote,just looked back at it. I will be takeing my meter home today and checking for contunuity from the tps connector to the ecu,and to ground. Also makeing a better jumper while I am here at work. . Gonna solder 2 male ends on a peice of 18 wire...still need to wire in that rear sensor tho...lol.

 

[WonIt]

Ok,so i bought my meter home with me today,along with another piece of wire to jump the 2 pins on the tps connector. i still got the same results when using the jumper wire(code 51 did not dissapear). also with the key turned forward and the meter on the IDL pin of the TPS connector and the positive battery terminal i got around 6v.

when i checked for resistance across the same 2 pins on the TPS itself i got under 100ohms,i think it was closer to the 50ohms side. i am not sure where to go from here,i do not see anything else on JJ's page that i need to do,tho i will be re-reading it a little latter to make sure i did not miss or miss-read anything.

 

[jetjock]

1) When measuring voltage on IDL battery negative should be referenced. You should see 5 vdc with the key on.

2) When checking continuity on the other pin (E2) battery negative should also be referenced.

Assuming your jumper is making contact it appears your 51 is unrelated to the TPS. Again, checking each pin at the ECU will tell you for sure which one is causing the code but based on everything you've written thus far I'm gonna go with the neutral switch input.