I don't understand why my ECU on my 97 Maxima is always giving me different codes each time I test it. The first time I tested it for codes it gave me 0304 bad knock sensor, and 0303, front left heated O2 sensor. The second time I tested it (a week later), it said that I had nothing wrong with my engine. Then after I installed my 96 Technosquare ECU, two weeks after last checking the ECU for codes, it said I had 0707 (which should be normal because I do own a 97) and it gave me 0304, a bad knock sensor. So I waited another two weeks and the 96 ECU now says I have 0707 (which again should be a normal problem for 97 owners using 96 ECUs) and 0303, a bad front left heated O2 sensor. So what could be wrong with my car, does anyone have any advice?

 

Sounds like you have a bad o2 sensor ..

 

Sounds like your plugs may be fouled. Other than that get some spray on contact cleaner and make sure the contacts for the sensors are clean.

 

Yes. bad 02 sensor can trigger a knock sensor code. You can check ur plugs since it's free, and check ur 02 sensor contacts since it's free. But probably that 02 sensor. Chain reaction...bad 02 leads to a KS code.

 

0303
Diagnostic Trouble Code 0303 indicates a problem with the front Oxygen Sensor on the left cylinder bank. The left bank is also called the front bank. It is cylinders 2,4,6. A normal signal sweeps back and forth between 0.2 volts and 0.8 volts. This malfunction was detected when the Engine Control Module received a signal from the sensor which was a constant value of approximately 0.3 volts.

Possible causes include ...
- Harness or connectors (the sensor circuit is open or shorted).
- Defective Oxygen Sensor


0707
"0707" which points to the rear Oxygen Sensor.

Your Maxima has three Oxygen Sensors. Two are front sensors, mounted in
the Y-pipe between the exhaust manifolds and the Catalytic Converter. One
is a rear sensor, mounted in the exhaust pipe downstream of the Cat.

When both front Oxygen Sensors are operating normally the rear sensor serves only to keep tabs on the Catalytic Converter. That's the reason your engine is running well. The Engine Control Module (the computer) is not using the signal from the rear sensor to control engine management functions.

For more information about Oxygen Sensors go to
http://www.volksparts.com/o2sensors.htm

For specific information about replacing Oxygen Sensors on your Maxima see
the Chilton manual (page 4-13) or the Haynes manual (page 6-14).

In a different thread SprintMax said he got a great price on a replacement factory Oxygen Sensor from Vester Nissan. He didn't give a location or contact information. Perhaps he was referring to Vester Nissan of Clinton NC, 1-800-572-2005. Also www.buyoxygensensors.com

 

Thank you for your replies guys. So I should check the harness and connectors to the O2 sensors and check the O2 sensors. The only problem is I don't have any idea of checking these things. I guess I need to buy a Chilton or Haynes Manual. Does someone know where I can find one? Thank you for your help again.