My friend has a 1999 Maxima GLE A/T with 90,000 miles. So, the check engine light came on, we pulled the codes, reset it and the CEL came BACK on a week later with the same codes. They were 0510 (downstream O2 sensor) and 0304 (knock sensor). To my understanding, a KS will not cause a CEL to come on by itself, right?

So, we bought a knock sensor and just replaced it - a REAL harrowing experience.

Anyhow - if anyone knows ANY detailed information regarding knock sensor specs (resistance, i.e.) or what precisely the ECU does to the timing when it senses knock, I would appreciate it. I know it should retard timing - but how much? Does it matter the crank angle at which the KS hears knock regarding whether or not the ECU will retard?? We put the new one on and the engine knocks when you blip the throttle from idle. It gives one defined, distinct knock just as I hit the gas each and every time. Is this normal (it is 87 octane gas, which I know isn't good for these engines, but that's how it is at the moment).

New knock sensor (from NAPA if it makes a difference) resistance was 533Kohms and the old one was 1023Kohms at first, and then suddenly dropped to 565Kohms (possibly as a result of cooling down as the engine was still hot when we removed it - who knows??).

If it makes any difference, he hacked the intake tube in two and put a cone filter on it. Would that cause it to lean out as a result of the MAF sensor getting an inaccurate reading?? It did on my '03 corolla.

If anyone has any ideas at all, I'd love to hear them.

Thanks,
Trav

 

ewww..87 gas i used to use that on my old maxima.. until my new one..87 caused so much problems..aside from bad performance. Switch to full tank of premium see if it runs better?

 

Get a ODB scanner and measure the voltage on the 02 sensors, then you will know what your problem is. A bad 02 will cause the knock sensor to trip since your engine will be running in safe mode. A bad knock sensor will not always trip the ECU... but it can.

 

I thought the downstream O2 sensor was never used for fuel trim - only to check the cat. conv.

Anyhow - the knock sensor was bad, I discovered. I heated the thing up and watched the resistance on my meter. Hot, it would read 560Kohms (good). Then, as it started cooling down, resistance would fluctuate wildly between that and 1500Kohms until it got cool, then it would settle in at 530Kohms. That to me says it's bad because that's not normal.

Trav