Hey Guys, I just went to get my car inspected and I failed emissions.. .. these are the codes I got. I replaced the front O2's a while back and the codes didnt disappear...here's what I got. (1996 Maxima Se 5 Speed 140K)

P0500 - VSS
P0400 - EGR
P0325 - Knock Sensor
P0150 - Fr. Heated O2 Sensor Bank 2
P0136 - Rear Heated 02 Sensor
P0135 - Front Heated o2 Heated Bank 1
P0155 - Front Heated O2 Sensor LH bank

Could this hopefully be just ONE obvious thing - anyone have any ideas?

 

did you have these codes prior to the inspection?

Try resetting the ecu and see what codes come back. Most of your codes relate to your exhaust but the vehicle speed sensor is kind of strange. From what I've heard the ever so popular knock sensor can cause a lot of other codes to pop up. So that might be a decent starting point. After you reset your ecu get a multimeter and find out if the sensors are really giving false readings


Go through the stickies to find out how to check the sensors manually, here are converted numbers...
P0500 104
P0400 302
P0325 304
P0150 303
P0136 707
P0135 901
P0155 1001

 

replace all 3 o2 sensors, replace knock sensor and Vehical speed sensor. See if the codes clear, if something comes back check to see what it is. Try not to play with thr EGR for now.

 

i dunno what your speed sensor egr and knock have to do with the 02 sensors......but i guess the o2 sensors could be related?? Faulty ecu??

 

check ur 02 sensor fuse

 

tackle the o2s before anything else. Seems like pretty much all you o2 are shot. Did you reset the ecu after you installed your o2s a while back?

The VSS (vechicle speed sensor) wouldnt be affected by a bad o2. It more than likely will need replacing. Test it with a multi-meter.

Reset your ecu and see what codes come back. Then post back here (remember the ecu will need about 200 miles to recycle thru its checks)

 

Does it even run with all those codes? That wouldn't let the computer know the car is even running. My guess is a bad computer. Go to car-parts.com and get a computer out of a 95 5speed. It will definently keep you form getting and evap and egr code.

 

When you replaced the o2 sensors did you reset the ecu? which O2 sensors did u replace before and how long ago?

 

if your egr valve is stuck open itll cause a lean misfire that your knock sensor is detecting. your o2 sensors are picking up too much o2 because its not being burned and converted into co2. ya got me on the vss tho..

 

knock sensors detect misfires?

 

Fix the EGR first, as someone pointed out, if it's stuck open or closed you will run lean or rich which might be playing havoc with the o2's.

 

Thanks for all the great info guys, I think the EGR will be the first on my list - I changed the 2 o2's in the y-pipe about 1000 miles ago. I reset the ECU and it was ok for a couple weeks and then the CEL came on again. It just read "rear o2 sensor" so I left it thinking i would be replacing it soon - then I went to get inspected and all this stuff popped up.

 

Rear o2 is common, why did you go for inspection with a CEL?

 

I dunno if its different everywhere, but in MA emissions is every other year...so I thought I was OK. BUT if your sticker is older than a couple months, they have to do EVERYTHING again - something I found out after the fact.

PS: I hate the rearr o2 - its like 160$ if my memory serves me correctly.

 

anything else come to mind?

 

not to steal ur thread.... but if i reset my engine light witht he screw under the dash or watever, and i get my emissions test right away. Is is possible the car wont notice wats causing the light to come on before there done with the inspection.....

 

Nope that won't work. Your ECU will read not ready and they'll tell you to come back in a few days.

 

Some have been able to pass via that method, other havent. I believe if you reset it, and drive for about 100 miles, you should be able to pass. Dont drive up to get the inspection, and reset it in the parking lot then have them inspect it.

I accidentally did this for my sisters car and it worked. I was fixing her EGR problem. Reset the ecu, and no Cel, a day later she went for emissions and passed, the next day the CEL came back.

 

Sounds like you need some new o2's try oxygensensors.com their the cheapest i've found

 

Where would you guys say would be the best place to get the:

VSS and EGR valve?

 

Bad knock sensor can cause all of those to codes to display. Knock sensor malfunction can cause timing issues and in an OBDII car it can make everything go crazy. I've had the same codes on 2 97s and a 99 and changing the knock sensor solved the problem. If you had an auto tranny it would also make the tranny act funny because the speed sensor would be making the trans computer go nuts. Its hard finding a good technician that can spot the one problem. The master tech at my shop actually figured this one out when a customer of mine said the dealership couldn't figure it out.

 

I have a 5spd.

So I am thinking that first I will clean out the EGR, and then replace the VSS - if the VSS goes bad - what should I notice? Car *seems* to be running fine. Would you guys assume that the knock sensor was an accurate code or thrown from the EGR?

Thanks!

Chris

 

whatcha guys think? ^^^^^^^^^^^

 

BUMP for a friend

 

well if your EGR and O2s are bad you will run rich/lean and probably have some engine knock, throwing your knock sensor code. The things you have listed could possibly cause a KS code, but having a bad KS will most likely not have anything to do with the other codes. A ks code won't throw the CEL, but the VSS probably will, and then you won't be able to pass emissions, so you will have to get that sensor fixed.

 

VSS is either unplugged or most likely the speedo isn't functioning properly, get a new speedo head or entire cluster.

 

There is a lot of guessing going on in this thread, suggesting replacement of sensors, the computer and the instrument cluster. Its shooting in the dark though, esp since you replaced the oxy sensors just 1000 miles ago.

I would try and figure out if the car is running rich or lean. Pull the plugs out and inspect them - if you find a couple are black then chances are there is an injector leaking. If they are all black or white then check the fuel pressure to help narrow down on the problem before going down the black hole of forever replacing parts hoping one of them will be the silver bullet.

 

UPDATE!

This weekend I replaced the EGR and the VSS - still need to reset the codes and see what happens. I actually saw where the knock sensor is - and I dont wanna have to pull and replace it. I'll keep you posed but I appreciate all the suggestions!

 

oh yeah WTF is the best way to do that - I remember some dude saying he had his GF do it cuz she has little hands? Do I have to really crawl underneath the manifold to change that thing!?!?

 

You get to jam your hand underneath the intake manifold and into the V of the engine. One bloody hand and one broken wrench later, I still haven't been able to get that little ***** off...

 

On my 95 getting the knock sensor on and off was easy. Just reached in with my left hand, stuck a socket on it, and used a universal joint, extension and a regular wrench to remove it. It was easy! I dont have fatty hands but i dont have small hands either. Maybe its different on other years?

 

Not to jack the thread, but is it worth buying an OEM rear sensor? Or should I just go with the Bosch sensor from AutoZone?

 

i think most O2's are made by either denso or bosch OEM either way.

Did those faults come back yet to the OP?

on those knock sensors, are most likely hit or miss pending on your hand. I had my little brother snug up the threads on it so i had to do was just tighten it. his little hand went in and called it good in matter of seconds.

I think you need to replace all 3 o2's just due to it being fouled out (fronts) and old age ( rear)