NewCarScent

Another post about the dreaded PO133 code.
1999 EM1 with P2T-A11 ECU, fresh engine rebuild, New Toda style header, Magnaflow cat, and Greddy exhaust.
Both of the oxygen sensors are brand new NTK units, there are no leaks in any of the exhaust system and yet the code keeps popping up.
Short of replacing the ECU, anyone have any suggestions on how to get rid of this code?
Need the car to pass emissions so it can be registered.

TomCat39

Sounds to me that you need to resistance test the wires from the O2 sensors to the ECU.

I suspect you have a problem there based on all the new parts.

NewCarScent

Should this test come out to no resistance if everything is in good shape?

1999 Civic Si

I had/have the same issue, I was already over a month over due on getting my tags two years ago and I just kept resetting the ecu until it stayed off long enough to set the monitors and pass emissions. I am using a rmf v2 replica with a megaphone. My tags are about to expire again and I am trying to get my hands on an A12 ecu, from what I have read online that should resolve my issue. Worse case scenario I can apply for a mileage exemption for emissions, but then I can't renew my tags online. lol

I also will be replacing my O2 sensor again and moving it out of the megaphone and into the 2.5" portion of the header. I checked the resistance on all my wiring when I pulled the engine harness out and I don't recall seeing any abnormal resistance in the o2 wiring.

TomCat39

Not zero but extremely low like 2ohm maximum.

Even wire has resistance, just very little.

If you see 100 or more ohm on a wire, you might need to investigate that wire.

AWG wire size (solid)	Diameter (inches)	Resistance per 1000 m (ohms)
20	0.032	33.2
18	0.0403	20.9
16	0.0508	13.2
14	0.064	8.28

As can be seen in typical 20 AWG wire, 33 ohm per 1000 meters of wire. So if you see anywhere near 100 ohm, it's highly questionable.

NewCarScent

I have read the same thing about the A12 ECU but I want to do some more testing before trying to find a replacement.

I will test the harness and report my findings.