Seriously, does it really matter if we keep the heater wired? I'm really lazy.

My CRX came with a 1wire but it's being converted to OBD1 and I don't feel like getting under the car (I have a 4 wire bosch universal right now, but only signal is hooked up... not the heater)

I'm sure the heater extends the life of the sensor (somewhat), but My thinking has always been that CARB wants heated o2 sensors so that our cars start running at stoich a whole 20 seconds earlier...

 

I doubt it will work. I have code 41(O2 heater circuit failure) due to a blown chip in my ECU and let me tell you, the car is running SO bad sometimes I'd rather drive my lady's stock Nissan Altima. Limp mode is teh suck!

 

If your o2 is located to far down you header, it wont heat up enought to read properly and you car will studder and hesitate, well at least mine did. I was running a kooks racing header which put the o2 down by the cat instead of in the manifold. As soon I got a heated sensor all my hesitation went away. I actuall tapped into my greddy a/f gauge o2 , the car ran beautifully.

 

Hey TimoneX,

Could you email me more about your problem. I am having the same issue. I get both code 41 (primary oxygen sensor heater failure) and code 2 (secondary oxygen sensor). I replaced the primary oxygen sensor altogether because it was actually broken but when I replaced it with the new one the code was still there. I cleared the codes and everything and it keeps coming up. The secondary oxygen sensor is working ok, the heater element on it is fine. On the primary the heater element is getting 12 volts and I put a voltmeter on the primary 02 sensor signal and it stays at 0.40 volts and doesn't fluctuate. I don't know why, it's brand new. I'm wondering how you came to figure out it was something in the ECU. My ECU is chipped so it has been opened and the socket soldered in but that was quite a while ago. TIA... sluszcz@hotmail.com

s

 

A little more on oxygen sensors. Oxygen sensors use Yttria Stabilized Zirconia (a ceramic) as an electrolyte. The oxygen sensor is really like a little battery or fuel cell that runs on air and the extra fuel (carbon monoxide CO) in your exhaust. For the cell to output a voltage it must be hot....A hot cell has a high ionic conductivity. A cold cell has a low ionic conductivity and is hence a partial insulator....it does not output a voltage.

Under lab conditions...ionic conductivity of YSZ:

Conductivity.....Temp.....Temp
S/cm..................oC.........oF
about zero...........100......212
0.00002...............500......932
0.00010...............600-----1111
0.00100...............727......1340
0.01000..............838.......1540
0.02000..............900.......1832

A sensor "lights off" when its ionic condutitivity gets in the range of 0.001 to 0.0001 S that is between 500 and about 700 oC. Below this temperature the electrons just wont get happy and move thru the YSZ. So you can either heat the sensor with its built in sort of self regulating heater, or put it nearer the exhaust manifold. The trouble with you turbo guys is it won't survive between the head and the turbo. You need to go in the downpipe perhaps 24" or more from the turbo in a gas environment that will NEVER get above 900 oC. Then the internals get too happy with heat and start to irreversibly change state......like busted.

The first generation of sensor, out around the late 1980 was a one wire unheated sensor, usually placed close to the manifold. The epa data showed that the cars emitted more unburned hydrocarbons and carbonmonoxide in the minute or two that that type of sensor took to heat up, than in the subsequent hour or so of driving. I know it does not seem like much, but heating the sensor does significantly reduce the emissions signature of our cars. Then again one WOT acceleration sort of dumps a lot of UHC and CO. Cold sensors (not lit off) makes the ECM unhappy when it tries to maintain closed loop.

All in all I would heat the sensor on a daily driver.

Regards,
BigMoose

 

I would say it makes the engine unhappy. The ECM doesn't give a ****, it just sees a signal saying the engine is running lean and trys to richen the mixture.

 

BigMoose,
Could you point me towards some more information on this. I've never heard of needing CO for the o2 sensor to work.

 

I'll put this here, because then more people can read it, and perhaps it will help someone else too.

Open your ECU and look for a burned IC. Sounds like yours and mine have very similar problems. I have a burned up IC labeled Sanken STA335A in mine. I've followed the traces to a green/red wire which is connected directly to the - side of the secondary O2 sensor's heater circuit. There is battery voltage across the primary socket and even battery voltage across the secondary socket and ground, but the secondary socket's - terminal is not grounded. There was also a blown resistor on this same circuit, but I have bags and bags of them.

I placed no less than 22 calls looking to find one of those chips. It seems that Sanken was aquired by Allegro micro a couple years back. Every dealer that claimed they could import those chips said they were $1.60 each, but I had to buy 500 of them! I think I have a line on a chip labeled STA335GM that a very pleasant secretary at Allegro said she would order for me in a repair/sample quantity(10). She THINKS they're the same chip or at least compatible. I should know tomorrow.

 

http://nunext.nuhorizons.com/NuNext/...mNumber=298058 They are $1.59 each in single quantities from Nuhorizons http://www.nuhorizons.com/ They offer them in single pieces, though they may have a minimum order dollar value.

I could not get the data sheet on the STA 335, but STA in Sanken represents a transistor array. If the part is 3 leaded it is probably just a bipolar transistor. I would guess a PNP pick something around 80 V and 5 amp and it will probably work.

Regards,
BigMoose

Regards,
BigMoose

 

I have the data sheet. It's an 8 leaded power transistor array. I'll try to recall where I got the pdf if you'd like to take a peek. Don't think nuhorizons came up in any of my searches. Thanks allot...I'll take a look.

 

Oh yes I did find that previously, and even built an account under my business name to order online. They sent me an e-mail stating that I had to order them in quantities of 500+, since they were "specail", and they do not stock them. That's when I got interested in contacting divisions of Allegro directly, and eventually got ahold of Whitesall & Associates. Here's a link to the data sheet if anyone is interested:

http://www.chipdocs.com/pndecoder/da...N/STA335A.html

 

Whoops you disabled instant messages..........I went to the site, and it looks like you need an account to get the data sheet. If you have an account with them, I would not mind a peek at the data sheet. If you can get it IM me and I will give you an email address to send it to.

If I can see the data sheet, I can try to get a work around if you cannot get the part. I always thought my data sheet service was pretty good, so not finding it, sort of tells me its discontinued or an "exclusive" type part.

Regards,
BigMoose

 

Ja it's a definite pain in the **** to locate. I think nuhorizon simply has not updated their site in awhile because the parts that the Allegro distributor ordered are labeled STA335GM if I recall. She could locate no reference to a part labeled STA335A currently in production anywhere globally. I believe the STA335A is extinct completely. Well it'll only cost me $20ish+ shipping for the 10 chips that are supposed to be in tomorrow, so I'll know if it works then if all goes well. Either way the car runs with the ECU...albeit in limp mode, AND I have a P28 at Hondata right now being prepped. One way or another I will get rid of this problem in the next week or so. I haven't used IM in forever, but I will throw this pdf on a net server for download so you can have a peek at it. It'll be at:

http://files.triton.net/timonex/sta335ae.pdf

shortly.

 

Thanks for the data sheet. Got it. Looks like they use it as a series pass transistor switch to power the heater on the O2 sensor like you said. By chance was the resistor that blew around 0.5, or 0.47 ish ohms?

Thanks again and good luck with it.

Regards,
BigMoose

 

You got it. I forget exactly but it was a very low value. Under one ohm.

Nope thank you.

 

Hey TimoneX,

I opened up my ECU today and I see that ST335A chip you were talking about. Mine doesn't appear to be burned out though. Did the connections to the board look really burned out on your? Just wondering how you knew it was burned out. I've played around with chips and making op-amps and stuff but don't know as much as you do about boards and chips. Everything seems to look ok, no resistors burned out either. What was the resistor location on the board? Any other help you've got or anyone else would be appreciated. I hate electrical problems!

s

 

Well I like electrical problems, if there HAS to be a problem. At least electrons always flow in a predictable manner. Well the wire going from the (-) side of the heater circuit on my secondary sensor to my ECU led right to that chip, so that helped. My chip is cracked and blackened on back, there's absolutely no question it's dead. The resistor in question is downstream from pin 5 on the Sanken chip. It's R165.

 

You have a '94 ECU though...don't you? There will definately be some differences if so.


[Modified by TimoneX, 2:50 PM 9/23/2002]

 

no, mine's a '97 p72. My ECU looks ok. Hmmm, don't know what else to do. Replaced the primary 02 sensor to fix code 41 (primary 02 heater circuit) and still getting the code after several ecu resets. Hooked the voltmeter up to the heater circuit and it's getting 12 volts. I've run out of things to check. The only other thing I can think of is the haynes manual I have said the resistance for the heater circuit is supposed to be between 10-40 ohms. I just got a 4 wire Bosch 02 sensor and the resistance was only 4 ohms. But, it was brand new so I didn't worry about it. It's still getting the right voltage though. I wonder if adding a resistor in series would help that problem?

s


[Modified by stevel, 6:25 PM 9/23/2002]

 

hi TimoneX, when you get those chips, do u think I can buy one off you?

 

Adding a resistor will certainly drop the voltage. Not sure it will cure your problem though. Sounds like it won't hurt to try. Put in a 10 ohm resistor, since the OEM sensors are supposed to have a resistance of 14.

NO dc2gsr94 you may NOT buy one from me!

If you pay the shipping though you can have one for free though.

Damndest thing I ever saw. The regional sales manager for Whitesell & Associates calls this morning and asks if I'd like him to mail them to me, drop them off at my house, or at my office. I could not believe it! So he did just that, dropped off 10 brand new chips at my home...now that's service. He wouldn't even accept money for them. I told him I'd have the Mrs. build some kind of confection for them over there. Drop me an e-mail dc2 and lemme know where you'd like a chip sent.

timonex@starband.net

 

Hehe ok well regardless I guess I'll just hook the heater up

 

Good call.

Nice sig too.

 

The oxygen sensor is basically a fuel cell. But it does not generate a voltage based on CO and O2. Rather, it generates a voltage based on the difference in O2 concentration between the exhaust stream and atmospheric air. Remember that reduction potential is a function of concentration as well as species. So a difference in concentration alone will genreate a voltage.

 

I would have thought you cut & pasted that if you didn't mispell generate at the end there. lol