Code 51 Help!

[cesupra]

I am new to diagnosing these codes. From what I've found code 51 means there is a problem with "Switch Condition Signal". Can anyone elaborate on this?

My car runs fine. I'm just having a tough time passing my smog test and the check engine light comes on after driving for a while on the freeway.

I have a:
1988 Supra non-turbo (7M-GE engine)

Any info on this would be greatly appreciated! Thanks

 

[theKnifeArtist]

i had code 51 cuz my tps wasn't adjusted. could be different though.

 

[Joel W.]

Take a read through these threads, They should help you.. See the TSRM on page FI-103 for how to adjust it

http://www.supramania.com/forums/showpost.php?p=205665&postcount=15

http://www.supramania.com/forums/showthread.php?t=16887&highlight=code

http://www.supramania.com/forums/showthread.php?t=17844&page=2&highlight=code

 

[jetjock]

Joel, will a code 51 illuminate the MIL? (page 136)

cesupra: What other codes did you have? What are your emissions numbers?

 

[Joel W.]

No it should not..It will only display a code 51 when the jumper is connected in diag mode with the ac on, the car is out of park, or when the gas pedal is depressed. If code 51 is there without the gas being depressed, ac off , and in park, then the TPS needs to be adjusted.

No check engine light will come on from a tps when driving normally I think..(maybe code 41 in California cars) And this is also tps related..

Final answer..

 

[jetjock]

You got it. Code 41 maybe, depends on the car. Look at the notation. This is why you should check codes on occasion and not rely on the MIL to tell you something is wrong.

Code 51 monitors the idle switch in the TPS. Code 41 is the pot for throttle position. Two independent parts of the same gadget with two different functions. The ecu needs to know what position the throttle is in but it also needs to know when it's completely closed. The idle (IDL) switch in the TPS is what tells it.

Used for lots of things, one of which is turning on the idle speed control system. It also tells the ecu to use base timing when the diag block is jumpered. Since you shouldn't be setting timing with the throttle open the ecu requires IDL to be closed. That way it "knows" the ISC if active and controlling idle speed to what it should be when adjusting timing.

 

[Joel W.]

I had a good teacher..

 

[cesupra]

Wow great info! Thanks for all the help. I will look into these things. I am a novice on most things here but I am a quick learner. About 2 years ago I had my supra serviced at a Toyota Dealership and they recommended replacing the air flow meter. I know there is a separate code for the air flow meter but would a faulty air flow meter produce a code 51? Code 51 is the only thing I am getting.

I was getting a code 11 but after resetting the ECU I don't get that code anymore.

 

[Joel W.]

No, the AFM can not set a code 51, Again, with the diag block jumpered, the key on/engine off, the AC off, tranny in park, linkage fully closed now look at the codes.

If it still flashes a code 51, then you have to adjust your TPS or something is keeping the throttle plate open and this is why you see the code. Does that make sense?

Code 51 is not stored in memory, so what ever is setting it off is happening now..

It could be who ever worked on it last got the throttle/cruise cable too tight, or the linkage out of adjustment keeping it open slightly.. If you can verify there is some loose play in the cables that will help narrow it to the TPS adjustment.