Ok I have a 1990 CRX SI with a code one. first thing I checked was the voltage signal with the O2 sensor pluged in and that gave me 0.1V. Then I unplugged my O2 sensor and checked the reference voltage going into the sensor and that was 0.1V. So then I went to the ECU and checked voltage coming out of the ECU (pin C16 White wire) and that was 0.1V. Can someone point me in the correct direction of where to go from here?

 

 

Thank you for that info. But just one question if I follow these steps and say the fuel pressure is correct and move on to disconnect the O2 sensor and then hook up my lead to the O2 sensor plug and my other lead to ground, how does the sensor then produce voltage? I thought there had to be voltage going in to it.

 

the O2 sensor produces its' own voltage by a chemical reaction between the exhaust and components within the sensor

 

So I followed all steps on the above procedure and my fuel pressure was at 38PSI and with the vacuum line connected would drop to 28psi, the voltage coming from the O2 sensor would pretty much flat line unless I hit the accelerator or spray starter fluid in the intake manifold. Please watch video. I did detect a very small leak in the intake manifold would that cause the O2 sensor to behave this way? I believe it to be very small because when I would spray around the intake manifold I would see a little spike in the voltage but would not cause any change in the engine.

https://www.youtube.com/watch?v=lX2e...ature=youtu.be

 

Changes in manifold pressure due to leaks can definitely have an effect your 02 sensor's reading.

 

I fixed the leak in the intake manifold but I still get the same code. is my fuel pressure to low? Fuel pressure is at 28 PSI with the vacuum line connected and 38 with the vacuum line disconnected.

 

How does your pressure compare to the specified pressure in the troubleshooting guide?

 

on the guide it says pressure should be 40-50psi with the vacuum line disconnected, so im 2 psi lower

 

so almost 7% low fuel pressure. If the injector is rated at 240cc/min at 43.5 psi, at 40 psi it is flowing 230cc/min. At 38 psi it flows 224cc/min, meaning over 9% less fuel than the engine is expecting. Is your fuel filter in good shape? it is possible that your pump or filter is slightly clogged or the pump is just not flowing enough. Some of hte older manuals have a test where you prime the fuel system into a measuring cup and see if there is enough volume to meet the spec.

 

That maths isn't right. For starters your injectors wont ever run anywhere near 100% duty cycle on a factory motor, and the relationship between fuel pressure is not a direct correlation to injector flow rate.