Why does a bad knock sensor show two different codes??

Question

Last summer, I bought a '97 Nissan Pathfinder with only 151k miles on it.  Soon after I replaced both valve cover gaskets (154k), the check engine light came on.  At 156k, I replaced the Oxygen sensor (bank-2, sensor-1).  Check engine light goes away.  After about 300 miles, it comes back on.  Scan results at Pep Boy's were P0325 (knock sensor), P0150 (oxygen sensor; bank-2, sensor-1), P0325 - P (knock sensor again with a 'P'), and P0300 (misfire detected random cylinders).

To start with the misfire, I installed a new set of spark plug wires before I installed a new knock sensor and harness.  Before installing the new knock sensor, I disconnected the negative terminal of the battery.  I wired a new harness to relocate the knock sensor to the top of the engine (under hood).   It started up just fine and I drove it around for about 10 miles.  I went to get it scanned to make sure everything was ok and the two knock sensor codes still came up (P0325 & P0355 - P)...BUT, the other codes for oxygen sensor and misfire were GONE!  I told the mechanic at PB's I just replaced the knock sensor.  The mechanic said he's not supposed to it, but because I was a nice guy, he would erase the codes !!!

My questions are:
*  Why was the knock sensor showing TWO different codes (P0325 & P0325 - P) ??
*  And, is my car really in the clear now since the faulty codes were erased after the new knock sensor was installed ???

Answer 1

The "P" means pending,  which means the code is not fully mature, when it comes to a knock sensor code it is unique it will not turn the CK ENG LT on because it is a one trip detection. One of the job of the ECM is to look for open circuit, short circuit , grounded circuit, and rationality, unless the knock sensor has a open circuit grounded circuit, it will turn the CK ENG LT on.

Comments

Thanks for your time, Reynaldo.  So, I should be good now, correct??  Or, should I expect the 'Service Engine Soon' light to come back on after driving it for so many miles??

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This type of year vehicle when dealing with a Nissan all had pending knock sensor codes, which they do not turn the CK ENG LT on. unless you have a open circuit , a short circuit or a grounded circuit , When it comes a Knock sensor code low coolant fluid level or cooling system problem can set this code. There been times being a truck that a rear hitch rattleling set a knock sensor code. If you drive and there is no CK ENG LT but a pending knock sensor code that going to be the norm.

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Thanks again, I really appreciate your time and insight!