So I have my emissions test coming up in Oct & decided to have the SES light & slight gas smell I sometimes get checked. Modern Tire did a diag & here's what they told me needs to be replaced:

- Knock sensor
- EVAP purge solenoid
- The fuel tank where the fuel pump sites may be corroded causing the smell, if that's the case, replace fuel tank. Been told this is common for Nissans
- Fuel filler neck & O-ring if need be once the tank is dropped

Total cost for all this $2500!! minus the diag fees. YIKES! How difficult are these to replace on a scale from 1-10? Would appreciate any advice from folks who may have already done these.

Thanks!

- Suresh

Oh Man that sucks Suresh
I'll look into it.
There is a gas tank for $125.00 in VT. that I found.
the purge valve is not hard. but the mounting bolts may be seized.
Knock sensor codes seem to be very common, Sensor is like $118.00 Damn
I have not changed one yet.
but I think it is under the intake on that engine.
Should be able to clear the code and do a drive cycle 10-15 miles from cold start
stop and go and criuse at 40 -45 mph for 3miles should clear most the emission monitors.
the fuel type codes are two trip monitors so it would need to be driven twice
for them to clear.
If after that no SES light you are good to go if you have a scan tool you could check the monitors before the test to see they are clear and completed testing.

I'll let the others chime in on this one on what they have done.

The knock sensor is ubiquitous with first gen Xterra's. It's a PITA to get to an replace.

Do what I did and relocate it. The stock sensor is in the "V" of the engine, very hard to get to. I replaced it in the stock location once and will never do it again. I have not had a problem since I relocated mine. I have a post in here in how to do it. You can also go to a Subaru dealer and get the same knock sensor for around $60. I can't remember what vintage, but they are the same. Really all any sensor has to do is send the correct voltage to the ECU to keep it all happy.

The knock sensor alone will not trip the SES light.

You can check the fuel tank by lifting up the rear passenger's seat. Access to the tank is right under there. If you have gas smell in your truck, the gasket may be bad, but there is easy access. You don't need to drop the tank to check it. The purge system is just inside the rear passenger tire. A black plastic box.

Thanks Scott. I checked the tank, there some rust around the rubber seal but not sure if that warrants a change. Would removing the seal & sanding the lip of the tank a little help?
Here's what it looks like:


What's surprising is the metal cover right under the rear passenger seat is pretty rusted, can't figure out how that's happened.


Scott - is the EVAP solenoid located the plastic box?


Tried a little to pry it open but couldn't figure out how to without breaking the clips. Will look for the knock sensor article & see if I can replace that too. Sounds like a busy few weekend.

Thanks!

Can you smell gasoline above the seal on top of the gas tank? I would start there and see. Another place you may want to check is the fuel filter. It's cheap and easy to replace, and if it's producing back pressure, that may be an easy fix. I'll bet it has never been changed. It's inside the frame rail on the passenger's side, between the front and rear door.

If you can smell gas while the truck is running, I would try replacing the gasket and the fuel filter. Not sure about sanding. Once you have the gasket, and take it apart, you may find the actual surface is fine.

The charcoal filter is in that black box...not sure if the solenoid is next to it or inside, but I believe it is inside.

Is your gas tank leaking? check for that as well, also, while replacing the fuel filter, check the fuel lines for rot.

Update on my emissions troubles - so I've been struggling with my SES light coming on & emissions leak codes being thrown for many many months now. Replaced the charcoal canister, various values, hoses, in & out of mechanics, etc. etc. to no effect.

After the NEW Snow run in Feb, something must have taken a beating because the SES light went away & didn't come back for a week. Cleared the codes & waited another week... no light, no codes. Had the emissions test done... and it passed

Now, after a couple of power washes, the SES light is back on with the same 'small leak; code. I'm ignoring it this time. Two dinged doors was apparently the price to pass my emissions

We'll have to bang it around and give it a mud bath on the 7th
it fixes all my problems, and then the 4runner is all one color

Sometimes pressure washing makes more problems than it fixes.

After wheeling sometimes I get a CEL. I'll still wash the engine compartment and then pull any connectors I can find and blow them out with compressed air and add some dielectric grease. Usually, after a week or so, the light goes away.