Hi, my 2000 Accord with a 4 cyl F23A1 engine has the CEL light on with a DTC of "O2 sensor heater circuit, bank 1, sensor 1". I replaced the primary sensor after checking for power to the connector. I turned the key on, then checked with a VOM to see if there was power at any of the pins. 1 pin had 12v (I don't have a wiring diagram). Going on this, I assumed the sensor was bad.

After replacing the sensor, I still get the same DTC and CEL light. I've reset it several times. Same DTC. To further complicate matters, I also noticed that the new sensor I put in is for a F23A4 engine instead of the F23A1 that's in my car. Would this make a difference?

Any help would be greatly appreciated.

 

Go into the MOTOR Magazine archives, Sep and Oct 1999 and read up on the Honda LAF Sensor. Let us know what you can figure out please.

 

Thanks Duane. I researched the articles you mentioned. I read over them, and I think that I have a plain old 4-wire heated O2 sensor in the Accord. Not the 5-wire like an LAF sensor.

 

Go into Motor Age Magazine archives, Apr 2002, O2 Heater Chase, see if this one will help then, its O2 heater diagnosis.

 

A little more info: I found that the first O2 sensor I changed out was for a F23A4 engine (California emissions, I think). Mine's a F23A1. I don't know if this would matter, but it did not fix the problem. I've got a wiring diagram and have confirmed power to the heater circuit of the sensor. I get power with engine running when I go from the power pin on the harness to chassis ground. However, when I jump the two pins at the connector, I get no voltage. The diagram shows that wire running back to the PCM, so I don't know if it's SUPPOSED to complete the circuit or if there's circuitry inside the PCM just waiting for a signal.

FWIW, I reinstalled the original sensor and checked the heater circuit. With my DVOM set to 200 ohms, I get a momentary(<1 second) indication of about 150 ohms, then open circuit. I've been told I should get about 30 or 40 ohms steady on the heater circuit.

 

It DOES matter. The F23A4 sensor is a wideband sensor. Your F23A1 uses a narrowband. Get the right sensor!

 

Thanks. I don't fully understand what the difference is between the two, but I was wondering if the wideband sensor installed in my car would still throw the same code. I'm planning on getting the correct sensor, but I am trying to make sure that I don't have another problem first.

That's why I was questioning whether I should have 12 volts when reading across the heater circuit pins on the vehicle harness side. Like I said before, I've got voltage from hot to chassis ground with engine running, but not pin-to-pin. Thanks again.

 

The wideband sensor produces a 0-5v signal and requires a controller in the ECU to interpret the signal. The narrowband you need produces a 0-1v signal. Having the F23A4 O2 on your car is about as useful as having nothing at all.

 

Is the heater circuit different on the wideband too? The reason I ask is because with the wideband installed, I was still getting the P0135 heater circuit malfunction.

 

The pinout at the ECU is different, but the circuitry in the sensor is probably the same. Still, there's no way to troubleshoot something if you start with the wrong part.

 

UPDATE: I went through troubleshooting procedures and was getting to the point to where I was sure I had a bad PCM. I put everything back together one last time & the code was cleared! All I can figure is that there was a bit of oxidation on one of the connector pins at the PCM and disconnecting and reconnecting the connectors must have "wiped" the oxidation off. Thanks everyone for the help!