Trouble code removal =

I have always disconnected battery to reset the computer and then it takes a few drives for the computer to find the problem and throw code again. This Time I had not driven truck for about 3 weeks and also replaced EFI relay during this time and never drove it very far so when put everything back together it took two drives and around 50 miles for the engine light to come back on showing there was a code again. It's not like the engine light has stayed on! I have also fixed other codes like EGR before and computer resets every time with battery un-hooked and problem fixed. I've been through this before with dealing with codes and fixing them!!!

Even in the PDF that scope103 sent it says the "STARTER SIGNAL CIRCUIT" will throw code and it is under code 12 for my model truck in my book!

The E-FAN I wrote what advantages it gives in one of my replies and why I run them - 10 to 15 more horse power for weak v6 and a lot better gas millage and yes I tow my boat and camping gear with camp fire wood all over Oregon so better power is always good and heavy loads E-FAN HELPS.

I have not read the code yet but figure it's the same code 12 but will be taken it in to my local mechanic to have him use OB1 reader from his laptop which gives a much better read out them the 2 cross-over wires under hood! last time it went into much better detail of each code.....

I'm going to be researching the STA CIRCUIT today, My thought is that if I can get it dialed down to losing the signal to computer from Distributor then I can take it in for wire testing in shop on just what needs to be tested---- as I wrote before I took it to a Toyota shop for diagnostics and $445 dollars later and them having my truck for 2 weeks I could barely drive it home and they fixed nothing!

I have gone and talked with 2 specialist electric auto shops nearby and will test truck for $120 dollars an hour or $130 dollars an hour I would much rather have them just deal with wiring harness if needed then testing the ˟˟˟˟ out of things that don't need testing while I'm footing the bill----

I have done the research of trouble shooting wiring from electrical system to computer and found threads that show what color wire goes to what system at the computer plug-in harness"s beings there are 3 plug-in's at computer and it goes through every wire position and color so I know it can be done but that is above my pay-grade so to speak HA......

I do think I am down to the STA CIRCUIT AND WIRING HARNESS WIRES FROM DISTRIBUTOR TO ECU------- This might be something my local mechanic can help with which he only charges me $50 an hour for diagnostics which is one heck of a lot cheaper then 130 an hour I just need to get it to where the is working on the specific problem not looking all over trying to find something in a sea of confusion if that makes since!

I will have him reset code reader after we read it with his computer though just to be safe and make sure it is reset But what I have been doing with that I truely think I'm right over 475,000 miles of work on the truck....

Thanks for your reply-----

 

UPDATE =

When doing quick research of STA CIRCUIT it shows the exact relay above computer in passenger kick panel I already replaced 3 weeks ago - it shows sta from that relay going to STA in computer so i'm sure I have already trouble shot that STA problem unless there is another STA sender to computer from distributor!

As far as fuel system we did a new fuel filter first when this first happened 3 months ago thinking it wasen't getting fuel? THEN found it was no spark so put in new coil then found the igniter was the problem from heating up and shutting spark system down... Toyota shop did test fuel pressure when they had it and it was good! They also tested the cold start fuel jet system tested good.....So new EFI - FUEL FILTER - OPENING CIRCUIT RELAY "MAIN RELAY ABOVE COMPUTER WITH STA SENDER.....

Unless I'm wrong it looks like wiring harness time???

 

Pretty sure you've said above someone tested the STArt signal at the computer or something similar?

Do it again! Identify and locate the STA pin on the ecu plug, back probe (voltmeter lead inserted along side the wire so it touches the terminal) it's voltage with everything hooked up, turn the key to the start position.. What does the meter say? I should probably double check but I'm pretty certain its supposed to be battery voltage.

If you've cleared the codes and verified the cleared and you have a STA signal reaching the ECU plug and it sets the code again..
You have two options.

make sure the electrical connections are clean and tight at the ecu and try again. Still no go? Take the cover off the computer and check the signal voltage makes it across the plug and into the ecu. Still setting code and has signal?

Start offering up sacrifices to omnipotent entities. If your lucky you'll find a bad capacitor you can replace.. If your not lucky or you screw up any of the probing in the ECU or changing out a bad capacitor, you're going to need a new ECU because that sensor line input is dead.

 

PS obd1 is output only there is code you can send that resets anything.. Save your money buy a paperclip, learn to count the flashing light, and consult the FSM.

I just got through the long post where you mentioned it's an intermittent issue, this is a big sign somethings loose somewhere, its inside the ECU, or a wire sheath that's compromised.. Exposed wires tend to pop fuses so it's probably not that last one.

 

No such thing for an OBD-1 vehicle. (Well, I don't know about ALL pre-1995 vehicles, but there is no reset function for an OBD-1 Toyota.)

Resetting the codes IS a good idea. Just pull the EFI fuse for about 30 seconds. http://web.archive.org/web/201211190...85diagnosi.pdf (Or you could disconnect the battery, but then you lose the radio pre-sets, learned fuel trim, etc.)

 

I have 2 ECU'S and it does it with both of them I mentioned this in the thread a couple times! Yes I have the paper clip and have used it many times...I'm way past that! Last time I had it read or the only time I had it read with OB1 computer reader it went into way more detail then just 1 flash and then 2 flashes and looking in the book and reading code 12..... Tomorrow I will try and post what the laptop reads out that is more then just what the book list's under code 12....It sounds like it's wire tearing about for me now in the main harness starting at the wire to distributor plug where it connects with main harness. I will also have a shop test wires at computer outside of plugs by position and color code and test wires going to distributor and go from there!!!

I will report back...thanks for all the replies...

 

Best of luck

 

Well it was not code 12 so that code is finally gone! Must of been the E-FAN and the wiring going through the EFI wire.

Now it's back to code 71 which is EGR valve which has been thrown twice when this started and fixed twice but back to it....what we did last time is soak the EGR valve in my friends solvent tank for days and blew out hose's and EGR and put it back on and it cleared the code but now since it's back I'm doing research on the EGR TEMPERATURE SENSOR... those wires are tiny and old and we had wrapped them with tape already but maybe this is the main problem because the igniter heated up pretty good yesterday.

DAMN temp sensor is $124 at rockauto and new EGR valve is up to $175....

But hey at least I can say we fixed the no crank reading.....

It just is never ending..... \

 

Your EGR Valve could have a broken diaphragm that is leaking & causing the code throw. No amount of cleaning will fix that. If your EGR Valve is original to the truck it's 25 years old & beyond past due to be changed out. $175 for an OEM EGR Valve is actually a pretty good price. My OEM parts source says the normal retail price on it is $285.05:
https://parts.toyota.com/p/Toyota__/...562065011.html

 

Plan on replacing both the valve and temp sensor! I will be getting new temp sensor first at the beginning of the month for budget reasons.... then a new valve if needed....

 

Both the EGR valve and EGR temp sensor have FSM procedures for checking them.
http://web.archive.org/web/201204061...77exhaustg.pdf
http://web.archive.org/web/201003261...00egrgaste.pdf
You can replace them "on the blind," but that sounds like a good way to waste $300.00 I would certainly test them first. Keep in mind that your CEL codes refer to "circuits" not "parts." You could have a good EGR valve that wasn't connected to vacuum correctly, or a good temp sensor with a frayed harness. The FSM tests will point you in the correct direction.

Your choice.

 

A new valve might not be a bad idea. A big concern once they start to stick due to carbon buildup is due to carbon being very hard. This can gouge the metal bits which then makes it want to stick once the carbon blockage is removed.

Before I spent any money on that temp sensor I would definitely test it, being a very simple device it's almost impossible to break short of smashing it with a hammer. It's a simple thermister in a metal housing, heat it up and check its resistance vs room temperature.

Being that this is also maybe an intermittent issue I'll remind you that it's very easy to expand the female lug in an electrical plug like this just by removing it. You can cinch the female lug in a bit and it will bite the male lug firmly again, and you can do this a few times before the copper will work harden and snap.

Remember electrical connections require a firm connection between clean two bits of metal.

..
I don't know if it's been mentioned before in this thread, it's definitely a dead horse around the forums, PCV goo plus EGR gasses are a pretty good insulation along with other properties. This goop build up insulates the sensor and blocks the EGR port inside the intake. Since you've cleaned the valve already it might be a good idea to clean the upper intake also since its way cheaper than replacing the valve and sensor even if you trash the gaskets and need new ones (think it comes out to less than 30$ for those three OEM gaskets.)

 

Wow great information.... I was reading about the vsv and other temp sensors last night and these 2 pdf's really help put it all together. My friend told me that there was no way to check the temp sensor with an ohm's meter.... Looks like he was wrong!

We also cleaned the filters in the modulator not to long ago but now know how to test it right..... Also showing how to test the VSV is great for electrical....I'm trying to concentrate on the electrical first to make sure my igniter problem is gone for good. It heated up yesterday to 114 degree's and it just felt if I let it idol for another 5 or 10 minutes it might of shutdown so I'm not convinced the electrical problem is fixed! Thanks again for the information it's great stuff!

 

When my friend did the EGR VALVE last time after soaking for days he also blew out all hoses and intake but the intake is of a brand new engine and heads! He did say he got a lot of gunk out of some of the parts though! and yeah we replaced the gaskets when he did it! My truck was at his home shop where we do most of the work so I wasn't their when he put it back in but made sure he had new gaskets....Thanks....When we put the old EGR on the new motor somehow the main gasket didn't get put back on and I noticed it the first time we worked on it and looked through gasket kit of new engine and found it and made sure to put it on! But we have never really trouble shot the whole system and after reading last night on it found many more players in the game to check so all this is helping a bunch --- thanks and it reminds me of reading (BE PREPARED TO GET TO KNOW YOUR 3VZE VERY WELL) LMAO

 

It's great that you are taking the Igniter temperature in an effort to solve problems, but don't get too hung up on it. 114 degrees F is well with limits for operating temp for that unit. The better quality units out there, like Wells/Airtex & Standard Motor Products, are tested against failure from excessive heat up to 125 degrees C, or 257 degrees F. You're running at less than half that so nothing to worry about there.

 

WOW out of every thread and site I have researched on the net this is the first time any one has said anything about temps an igniter can withstand!!!! I actually asked in this thread does anybody know what temps an igniter should be running at or at what temps it is dangerous point of shut them down.....

You sir get the trouble shooting all-star award!!! Thank you very much......