Hello: After installing the header and getting it all set, I am getting these two codes. I reset them once and these two come back again. I will check for leaks etc and the reading on the first O2 sensor (7aFE engine stock, 1996 ST HB). What else I need to look for?

How do I check for sensor circuit heater?

thanks in advance.

did you put the O2 sensors back in?

did you swap them?

Might just be a faulty sensor or it might have a bad connection which could be remedied by re-plugging the connector. If everything was working fine before the new pipes were put on, most like one of these would be your answer. I'd imagine if it were leaking you would hear that especially under load considering its pre cat piping with no baffling to it.

Yes, It is back in and I had to use the oval type flange to put it back in. I did not swap the 02 sensors. The new one did not come with one.

igpx12. Yes everything was working before, I just wanted to add a header. So I installed one of these ebay headers with downpipe. I have to take the car to the shop to get two 3 inch SS pieces welded in so it reaches the existing cat. I plan on checking everything and reporting back

Oh, well if you have the system open ended like that, most definitely thats gonna throw a code cause your downstream is plugged in and attempting to get a reading in combination with the upstream basically creating an open loop. Once you get it extended and close the loop you should be all set.

Not sure I understand what you are saying. The downpipe that came with the header was short in terms of reaching the cat. So I took it to the shop and added a piece that took care of that. There is nothing open at the moment. i will check for leaks but other than that it should be all closed. So both 02 sensors are in. I did not even touch the downstream sensor. I separated the original before the cat replaced that whole piece with the new one.

What he was meaning was that if you had an open exhaust that's going to cause the code. You had 3 inches missing from mid pipe to the cat so that'd explain why it threw a code. Reset your ecu and see if the light comes on.

Thank You. I pulled the header out and notice the header to down pipe gaskit is leaking already. Perhaps I did not tighten the bolts correctly. So waiting for a different new gasket from O'Rielly and will install tomorrow.

The junk gaskets they give you always leak. I had an obx header on my old celica... the gasket kit they gave me fell apart in my hands once I took them out of the packaging.

You are so right about the junk gasket and this whole eBay crap headers as well. First it did not fit, I had to drill holes bigger to make it fit. Then the down-pipe was short. That got fixed then it threw the codes, and now the gasket leaked. So far my cost of buying SS pipe and shop labor is about the same price I bought it for LOL.

Hello Guys: I am facing a new issue. After I discovered the leak (bad gasket) between the eBay header and the down pipe, I am stuck without a gasket. No one, even the seller does not offer spare gasket for that pipe. I have been pushing him to get me a couple so I can have one spare. So far no luck. He says he does not have spares nor he knows the part number. (This was my worst buying experience).

here is the vendor I purchased from:
http://www.ebay.com/itm/Toyota-Celica-94-9...erformance-Race.

If you look at the bottom, the second smaller gasket is the one I need. The measurements are 5 inches in the center from one side to side; the width is 2.75 inches exactly in the center. The top two holes are approximately 3.75 inches center to center.

O'Reilly guys ordered some but they were smaller. I have found several similar on eBay and one has the measurements (showing ruler on it) that seems to fit and I have ordered it which will be here next week but fitment is not sure at this time.

Any help or input would be appreciated.

just buy the material and make your own.
do you still have the leaking one.
trace over that one and cut it out from this:
http://www.oreillyauto.com/site/c/detail/M...8&ppt=C0227

Here is what you want, it will fit with that style header and downpipe
I've had to replace the original one that came with them too.

http://www.ebay.com/itm/170832336685

Cheela: Thanks that was my second option.

Igpx12:

Awesome thanks a million!

OK after several gaskets I finally had to replace the studs on the header and install new gaskets. No leaks but the engine check light keep coming on after about 20 miles of driving. The O2 is still the old one. Should i replace the O2 at this point? This is frustrating because I cannot pinpoint the problem.

Any help would be appreciated.

Replacing the O2 would be your best bet, clearing codes from the ECU is only temporary and after like you experienced with driving, once the ECU tries to set values and calibrate it will pop the codes back up again. Last upstream O2 I got was from rockauto for 30.00 for a Denso.

thanks I plan on replacing the O2 sensor after i check the connections and wiring.

Most time heater circuit codes are just bad heater circuits, it's a little heating coil in the sensor and it does burn out with age. The fastest way to check them is with a noid light. http://www.amazon.com/Lisle-27800-Universa...ords=noid+light
Connect that to the heater circuit wires (the two blacks on the O2 sensor are heater circuit), it should flicker and flash when you start the car, indicating the circuit is working. You can also hold the O2 sensor in your hand out of the exhaust pipe and start the car and it should get rather hot in your hand.

OK I will try that and see what happens. I found prices of replacement denso on RA really cheap. about 33 shipped.

I prefer the 'direct fit' so they just plug in, assuming the $30 one is one that needs to be spliced into the wiring. Not a big deal as long as you do the splices properly and seal the connections from the environment so you don't rot out your wiring. If you do need to splice it, do it on the sensor side of the wiring so you don't donk up the engine harness!

Thanks, I think it is direct fit as I checked the local Advance Auto and O'Rielly and the sell the same part for 58 dollars. So it does have a plug two pin.
Thanks again.

That denso through rockauto is a direct fit option. I ordered one already a few months back

Update: Installed the new O2 Sensor last night. drove around the block, no check engine light. Drove to work this morning about 18 miles no check light, so will see on the way back if it does turn the Check Engine light. I will post back to see if the problem is fixed or not. So far no check engine light. It comes on after you drove it for 10 -15 miles and then idle it for one minute.

BTW the Denso was direct fit.

Ok the light is back ON after installing the new O2 sensor. Can someone please tell me how to systematically check the system to see where is the issue. Obviously, it is not the O2 sensor. I will check for leaks one more time. The new header has the flange type with two studs to install O2 sensor. I have replaced the gasket there. There are no leaks between the header and the downpipe.

1. So How do I check to see whether the ECU is sending the signal. I have a test meter.
2. How do I check to see if my O2 sensor is working properly.

I have to factory Manual for this car (1996 ST with 7AFE) but it asks for special Toyota SST which I don't have. YouTube University says to check for voltage at the ECU end and check for resistance at the O2 side. Is this correct. Any help would be appreciated.

Same codes?

Sorry Bitter for the delayed response. I was TDY. I cleared the codes after i installed the new O2 sensor. Since I drove about 230 miles and no lights so far. So it must have been the O2 malfunctioning. I will keep you posted if it does comes back on and I will check for the codes this time.

I have a Kiwi MPG installed in my car and usually use to monitor the coolant temp with it but it also clears the code. It does many other things as well.