Oxygen/Knock Sensors
 

I have a 1995 GLE with 71,000 miles. Within the last three weeks, my mechanic has done two diagnostic tests. The first test revealed trouble codes P0130/P0150 (oxygen) and P0325 (knock). The second test revealed trouble codes with only the oxygen sensors. However, he can't find anything wrong with the sensors and has simply reset the ECU. The car is driving normal and the engine check light hasn't come back on. If the sensors are okay, then what could be causing them to trip? Is my mechanic unqualified? Any ideas are appreciated.
Thank you!

Re: Oxygen/Knock Sensors
 

I have the same car. I just ordered both the rear O2 sensor and knock sensor. I am replacing mine because I reset it once and same codes popped up again. I would tell you that if the CEL goes on again, you need to replace the chosen sensor(s).

just check the codes yourself. there areinstructions all over this board on how to do so. we're lucky we can do this, as the 2000 and over folks (5th genners) supposedly cannot do this. i waslookin at my friends 2000 ecu and there is no screw to check the codes. keep an eye on the codes in the next week or two as the KS doesnt throw the check engine light.

Re: Oxygen/Knock Sensors
 

Your mechanic is not unqualified. Rather, he is playing things conservatively, in your favor. Allow me to explain: The ECU is not infallible - occasionally, it will generate an erroneous code for one reason or another. By resetting the ECU after a code is generated, he is in effect, giving the ECU the chance to reproduce the same
code(s) and essentially, verify that the code is pointing to an "actual" problem and not a software hiccup.

Aside from the inconvenience you'd experience with two separate visits, the cost for labor & parts would be the same whether he replaced the sensors during your first appointment, or waited for a secondary verification & replaced them later. So, he sounds like he's treating you fairly & knows what he's doing.

The point is, it's not uncommon for people to reset their ECU's after getting a DTC (diagnostic trouble code) and have it never reappear again relating to that problem. (No point in throwing good $ after bad, right?)

I agree also that the ECU does NOT trigger a CEL (check engine light) independently for the knock sensor. The only reason your mechanic found the knock sensor code, was because he got the CEL for the O2 sensor(s). So, even if your CEL doesn't come back on in about a week or so, you should pull the codes from the ECU to see if the knock sensor is still triggering a DTC.

See:

http://vbxmaxima.8m.com/ecu.html
and. . .
http://vbxmaxima.8m.com/ecudecoder.html

You can do this yourself - it's not that complicated & doesn't require a lot of time or special tools.

Good luck & welcome to the Forum!

:)

I also just did a new knock censor about a month ago and they are $$ luckly i got mine at nissan cost for $130, :D


p.s. my boy installed it in about 20 to 30 minutes


Jay from CT