Heated Oxygen Sensor

[johnb_009]

What exaclty does the Heated Oxygen Sensor do. What are its effects. I have a 94 max. and I was getting a Code 33.

Also, is the knocking sensor important?

[zagrot]

an exhaust gas oxygen sensor's temperature must be around 500 degrees before it can produce a voltage signal. older O2 sensors relied on the exhaust to heat the sensing element, but at idle the exhaust temperature would drop and the O2 sensor would quit making the voltage signal. the heated O2 sensor heats the sensor element so the computer can stay in closed loop mode. a bad O2 sensor can cause poor fuel economy, a rough or loping idle, and that annoying check engine light (and the fault codes that go with it)

the knock sensor is important, it senses detonation and upon it's signal the computer will adjust the ignition timing untill the detonation is no longer present. the knock sensor is not fool proof, it can be activated by other engine problems such as rod knock and piston slap as well as excessively noisy valve tranes (usually caused by failing hydraulic lash adjusters)

dunno about the code thing, but if i find my computer diagnostic manual i'll look it up.

[Nahkapohjola]

Originally Posted by johnb_009

What exaclty does the Heated Oxygen Sensor do. What are its effects. I have a 94 max. and I was getting a Code 33.

Also, is the knocking sensor important?

If engine runs fine, forget about the ECU lottery machine.
If engine does not run fine, ECU most possibly will not tell anything...

Knock sensor goes bad in time cuaisng retarded ign as already told, loss of gas & pwr; maybe bypassed with a resistor. --->Then its better to use high octane fuel.

To test sensors, look at
http://www.cardomain.com/memberpage/748507/9

and
http://www.cardomain.com/memberpage/748507/14

[johnb_009]

Where can I get those resistors you talk about in your web page on knock sensors. I been driving my car for a while on 87 octane. It really does that much damage?

[Nahkapohjola]

Originally Posted by johnb_009

Where can I get those resistors you talk about in your web page on knock sensors. I been driving my car for a while on 87 octane. It really does that much damage?

Radioshack or similar. I had 1MOhm on the self, just paired two to get 0.5MOhm. If u get smtg like 300-500KOhm, its enough from ECU point of view to think all is ok. Costs few cents, buy for testing.

The knocking kills the engine, pistons or rods or crankshaft, of course depends on severity and how much u load engine during knock. Most often its heard, but u have to know what to listen. Happen to know how engines blow... One has to pay for all learning.

Nissan installed the system to have globally easy, all drinking engine. Now if that feature is bypassed, one has to make sure no knocking happens by buying higher octane. Here we have only 95-98octane for sale, so no problem for me.

If u want still to use low octane, buy new KS if suspect yours is bad. In this respect higher octane means possibility for more HP [using more advanced ignition].