Help! - Code 51

[born2drv]

Looked it up in the TSRM:

Switch Condition Signal

No "IDL" signal, "NSW" signal or "A/C" signal to ECU during diagnosis check.

Trouble Areas:
A/C switch Circuit
A/C switch
A/C amplifier
Throttle Position Sensor Circuit
Throttle Position Sensor
ECU

-------------------------

Now I'm pretty sure this is A/C related since my A/C compressor will not kick on when I turn it on via the climate control, but when you give it 12V directly, it works flawlessly. I replaced the A/C compressor relays (near the fusebox), brand new OEM toyota but that didn't help.

So where do I start with tracking this problem down? Where is the A/C switch and circuit? Where is the A/C amplifier? Anyone had this problem before? I'd appreciate any help you guys can offer.

Thanks.

 

[jetjock]

Your code 51 and AC problem are completely unrelated. Focus on the TPS and search for recent threads about dealing with this code. And stop jumping your AC compressor unless you want to buy a new one.

 

[Joel W.]

JJ: I am certainly not doubting your instincts as it being TPS related.. but why does the TSRM refer to the AC switch/circuit/amp?

I know I am being lazy here but your so helpful...

 

[born2drv]

hey jetjock, i'm glad you chimed in because i know you're a smart guy when it comes to the A/C system.... so what do you think coudl be causing my no-ac problem? i've tried everything, the compressor will not kick on no matter what i do??? i mean i haven't.... a technician has, he can not find the source of the problem.... i have to take it to him again to troubleshoot some more.

i did just buy a new AC compressor by the way, toyota OEM... i've spent over $1k trying to get this damn AC to work, and still no go. The AC compressor and clutch were replaced... some switches or something were replaced, the evaporator (thing you look in) was replaced, the a/c relays .... it works perfectlly when you give the compressor power but we can't get the damn thing to turn on from the climate control.

i'll get the TPS looked at too.... i'll search the other threads regarding that, thank you.

 

[jetjock]

Yes my friend, you are being lazy. Not because the TSRM explains it but because I already have in several previous posts. But since you're such a nice guy I'll go over it again

The Neutral Start Switch signal and the AC signal share code 51 for diagnostic purposes. It's a method of verifying the wiring and signal integrity from those two items. The code is set when the diag block is jumpered and those signals are active. This is in contrast to a TPS IDL contact code 51 which the ecu sets when the IDL contact is open (not active).

The only way the AC system could be giving a code 51 is if he's trying to use it with the diag block shorted. He didn't say he was troubleshooting the AC so I'm guessing he sees code 51 with the AC off. That implies it's an open IDL contact. If he *is* trying to run the AC with the block jumperd then he *should* be getting code 51. Understand?

So yeah, I suppose if you look at it a certain way (which the TSRM does) the AC could be causes of a code 51. The confusion is because the TSRM implies a code 51 will be set when there is "no signal" from these three items. In truth it'll be set only when there is no signal from the IDL contact but will be set when there *is* a signal from the AC. It's just another case (one of many) where something was lost in the translation of the TSRM.

Nor will the AC set a code 51 just because his compressor clutch isn't working. All 51 means is the AC signal being sent from the climate control head is being sensed by the TCCS when the diag block is shorted. There could be several reasons for his clutch not working but the ECU hasn't a clue about clutch status. It only knows when the AC button has been pressed, in which case a code 51 is a good thing. The most likely reason his clutch isn't working is he's low on refrigerant and the low pressure switch is preventing the clutch from coming on. It could be a few other things too. The AC won't work if the ambient temp is too low for example.

It all comes down to what he's trying to do and why posting "help, code 51" doesn't tell us much. We need to know what state the AC is in when he gets the code. If it was on code good. If it was off code bad. Got it?

 

[Joel W.]

Ok that's fair... I have read most of your posts, but I still struggle with them. :biglaugh: I am just plain stupid sometimes. My Bad...:slap:
(at least i know this much) hehehe

I had to read this post like 6 times and NOW I am no longer confused. Thank you!!!...

 

[jetjock]

Nah, it's not your fault. Upon rereading the post I see it's accurate but a piss poor job of explaining. It's because I'm in a bit of pain from an mild infection and the hydrocodone is making me stupid(er).. Me thinks I'll rewrite it when I get a chance

born2drv: That's pretty sad when you fork out a grand and get no results. I'd find a new tech if I were you. While the climate control system in the car is fairly complex the part that controls the AC clutch on is not. The first thing you need to do is verify refrigerant charge. Either put a gage set on it or jumper the low pressure switch and see if the clutch pulls in. While your at it check for a code 51 with the AC button depressed and the diag block jumpered.

 

[SP 7M]

I just had a TPS go bad recently. Do you have any bucking, stumbling or hesitation under throttle? If you sit in neutral and rev the engine upward slowly does anything out of the ordinary happen?

I had bucking and stumbling and when that would happen I'd stop and watch the tach closely as I gradually increased RPM. My revs would drop off instead of continuing to increase.

There is a troubleshooting method in the TSRM to see if the TPS is bad or not, too.

If I repeated anything that anyone has already said, then I apologize. I didn't really pay attention to them.

 

[Joel W.]

Nah, it's not your fault. Upon rereading the post I see it's accurate but a piss poor job of explaining.

I rather liked your post, as it makes the TSRM much clearer to me now. It is my fault like I said I have poor comprehension skills when reading.. I am working on it..

So to sum up my comprehension skills, (KOEO) key on/engine off

KOEO + jumper + A/C button depressed = code 51
KOEO + jumper + NSW(out of park or neutral) = code 51
KOEO + jumper + throttle depress = code 51
Code 51 with no gas depress, no ac and in park = adjust TPS
Check light on when driving = code 41(cali only) bad TPS pot

 

[jetjock]

Yes but a more accurate description would be IDL contact open or bad rather than TPS. Remember, when trouble shooting the TPS should be treated as having two independent functions becasuse it does.

Now why didn't I simply write that? Because you wouldn't understand the why of it. The TSRM is lacking in that it tells you possible causes for codes but it doesn't explain beyond that. As with any service manual the TSRM writers made an assumption the individual working on the car possess a certain amount of knowledge beforehand. For example they may tell you a shared code will be caused by the AC system but it's up to you to understand the why behind it. I can tell you the logic behind the setting of any code, what events and how many times they must occur to set one, which will be displayed on the MFL and which won't, and a host of other diagnostic details.

Then there are the odball cases. It's entirely possible the tech who was attempting to repair his AC mucked up the wiring. This could cause a code 51 when it shouldn't so in that sense it *could* be AC related after all. I'm simply assuming the car is still wired as it came from the factory.

One thing I neglected to mention is the purpose behind the AC and NSW signals is for idle control. It's why the ecu monitors them in the first place and is why the Toyo engineers included them in the diagnosis software. That's not true of all ecu signals however. Oil pressure is one example. It's also used for idle control but won't isn't included in the diag rountines.

Lastly, I'm obliged to point out the post above yours only serves to muddy the waters. It's impossible for what he's describing to be the cause of born2drv's symptom. I undestand the intent was to help however.

 

[born2drv]

born2drv: That's pretty sad when you fork out a grand and get no results. I'd find a new tech if I were you. While the climate control system in the car is fairly complex the part that controls the AC clutch on is not. The first thing you need to do is verify refrigerant charge. Either put a gage set on it or jumper the low pressure switch and see if the clutch pulls in. While your at it check for a code 51 with the AC button depressed and the diag block jumpered.

OK - the refrigerant is fully charged, so that's not it.

When you say jumper the low pressure swtch to see if the clutch pulls in, you mean run a wire from either end to by pass it? I don't see a low pressure switch in the TSRM, I see a dual-pressue switch, is that the right one?

As for jumpering the diag block and depressing the AC button and checking for 51... you mean the diagnostic block behind the fusebox? So I jumper the E1 and TE1 with the AC ON and without the car running, and check for a code 51 is that correct? Should I clear out the codes first?

Sorry if these seem like basic questions but I'm not really used to troubleshooting electrical issues plus I want to make sure I'm doing it correctly.

If Code 51 doesn't show up when I do that, what does it mean?

 

[jetjock]

How did you establish the AC is fully charged? If it is the dual pressure switch is probably OK but check it anyway. Jumpering the switch means to unplug it's connector and use a wire across it. Or ohm the connector side of the switch and see if you have continuity. For now we need to treat code 51 and the AC problem as separate issues.

Under what conditions are you getting code 51? Is the engine running or not? Is the diag block jumpered or not? Is the AC on or off? Does moving the shifter change things?

Yes, anytime I mention the diag block I mean the thing near the fuse box.

Do this: Jumper T and E1. Turn the key on and make sure the AC is off. What code appears? Answer that and I'll tell you what to do next.

 

[Joel W.]

As with any service manual the TSRM writers made an assumption the individual working on the car possess a certain amount of knowledge beforehand.

I can not agree more on this. It seems to apply to most manuals I have tried to read. I need the "TSRM for Dummies" copy. Not that I am saying anyone who does not understand it is a dummy, but it holds true in my case. LMAO

Thanks again for your time and efforts here...

 

[jetjock]

I'll tell you something though. As far as service manuals go the TSRM is one of the very best I've ever seen. There are very few these days that offer the information it does. In a knowledgeable person's hands it's an excellent manual. It doesn't tell all though and is why I've over the years chased down internal Toyo publications and other documents to resolve a mystery when I've come upon one. But compared to a generic manual like a Haynes the TSRM is a very nice piece of work. Why anyone would attempt to work on the car without owning one is beyond me.

 

[SP 7M]

Lastly, I'm obliged to point out the post above yours only serves to muddy the waters. It's impossible for what he's describing to be the cause of born2drv's symptom. I undestand the intent was to help however.

Exactly. My intent was to help whether it does or not.

I don't pretend to be an expert and never have.

The waters are clear as far as all that goes.

 

[B shaw]

Sorry to revive an old thread but I did find it useful. Codes have been pulled and cleared. They have been pulled again and with key on, car not running, ac off, and not touching the gas pedal the only code I get is 51. I'm fairly certain it is not related to the ac at this point. I know I said in a previous post I thought it was, but as it turns out I was wrong about something that was done between my buddy and myself in the process of removing/installing engine. I'm on lunch at the moment, but will grab the tsrm and go to work with the tps adjustment, unless there is something else I should be doing. At this point the tps is all I know to work with. Please excuse my lack of knowledge with the supra. I'm far more familiar with the diesel vehicle the military uses.

 

[jetjock]

http://www.supramania.com/forums/showthread.php?46793-Code-51&highlight=code+51

 

[supraguy@aol]

Ok, i just laughed out loud.
I was sitting here, reading JJ's responses with my mouth hanging open.
I couldn't for the life of me, figure out why he was so friendly and amicable.
Then i realized it was 7 years ago!

 

[Grandavi]

Ok, i just laughed out loud.
I was sitting here, reading JJ's responses with my mouth hanging open.
I couldn't for the life of me, figure out why he was so friendly and amicable.
Then i realized it was 7 years ago!

rofl...

ditto

:icon_bigg

 

[jetjock]

So I've gotten a little grumpy. Don't worry, it'll happen to you...