'96 Nissan Maxima W/MIL on; Codes P0325, 0500, 0600 - HELP!!

Approx 119,000 miles on vehicle. Absolutely no driveability/performance problems. Bought car (10/05) with MIL on in CA figuring it wasn't too serious. Drove car to & around Oregon-MIL went off w/out my doing anything-passed DEQ for relicensing, then some time later MIL comes on and remains on. Two years later due for DEQ/emissions test/relicensing & MIL is on, get codes P0325 & P0500 (knock sensor & VSS)-clear them & install new speed sensor (on trans-Wells #SU6475) along with new battery, starter W/solenoid, spark plugs; cleared codes & tried state emissions (DEQ) & registers "Not Ready" on Catalyst, Evaporative, and O2 Sensor checks. Continue to drive for work/shopping trips etc. and after 3-4 trips MIL comes on again. Clear codes 0325 & 0500 again, drive, and after about 3 on-drive-off cycles MIL comes on again. This time same 0325, 0500 plus P0600. Also, going back couple months or so, sometimes when starting the OD (Overdrive) dash light flashes several times & I might add the crusie control function would kick out after driving on crusie for only a short distance, mile to 2 or 3. P0600 I believe is AT Communication error? Is there a "Trans Comm Module"? - Where?

Took car to a "Foreign Car Specialists" for a fix: They pulled same codes and did some checking, like continuity and/or what I don't know exactly yet as they still have the car, but they said they could find "nothing wrong". Don't think they checked output of VSS nor resistance at knock sensor but I think they're both good. From here they said they could check each value or pin at the ECM which would take 2 to 3 hours and be
"expensive". Aargh! Not what I wanted. I'm scared to take to Nissan dealer for costs with probably lots of R & R's of good parts and still get nowhere. Plan to pick it up tomorrow and do what I can to check it out, connectors and the like, whatever I can do, but I sure could use some pointers and very grounded suggestions.

The car runs perfect, no pinging, misfires, starts immediately, no smoke, speedometer functions fine, havn't tried cruise control for a while, just that damned MIL on and the codes and trying to get it thru a sufficient "drive cycle" (whatever the heck that should be or include) to pass state emissions. I can't quite accept the fact the ECM might be bad as the car runs so good in all respects. Can I disconnect the wire terminals from the ECM and then reconnect just to clean them without messing up any stored data or anything? Sure could use some KNOWLEDGEABLE assistance on this problem, or direction to someone in the Portland, Oregon area who knows their stuff on this car. Thanks in advance for any assistance anyone is willing to share.

Yeah because paying someone to work on it for 3 hrs and them telling you nothing is wrong but the light is on is so much better then taking to the expensive dealer! Wake up and quite being so stereotypical about the dealer! they work on them all day everyday! Even if they cost more do you really think they're going to say something as stupid as "there's nothing wrong with it! Enough with the dealer assumptions and bashing!

^Off the coffee, bro. lol

Seriously, though. You have two issues at hand; you NEED a new knock sensor. Common problem with a32/a33 maximas with the vq engine. Not too hard to change, the intake does NOT have to come off and don't let anyone tell you differently. Also, the instrument cluster in your maxima has a small internal intermittent connection issue. You can replace it, or go to someone who has done this and have them take it out and tighten the screws on the pcb mounted in the cluster. This will restore proper continuity.

Jeff is right, the dealer isn't the devil here, but rather poor technician examples working at dealers who made poor decisions in hiring.

Jeff Compton: You're absolutely correct, and I should know better than to go by "stories I've heard" rather than actual experiences. Nissan dealers and their techs know Nissans and are trained on them so that's where I should have gone, and will as soon as I pick up the car from the "experts" I was directed to. No more dealer bashing from me. Thanks for responding and you have my apology.

Wyldemannn-Thanks for the response. Wouldn't the engine run rather poorly, especially under load, with the knock sensor bad? Car runs fine.
Can instrument cluster be pulled out far enough to check/tighten connections without bothering air bag circuitry?

Any shop that doesn't know about the knock sensor issues on Nissans is no kind of specialists but more then likley tire and brake specialists that cater to import drivers who can live with the light on because they don't want to pay the higher door rate at dealers! Don't be snowed! The days of "specialists within the industry are dying! if the shop you go to can't repair everything on your car from stem to stern and instead you need 2 or 3 different facilities for oil changes, tires, diagnostics, exhaust etc then you're going to the wrong facility!