Recently had my 60K factory maintenance check on my 02 4x4 5sp SC X and asked them to investigate why my engine power seemed so poor lately...

They said that the supercharger relies on a knock/detonation sensor, and that mine was blown. The supercharger apparently shuts down when it doesn't receive a signal from the sensor. The sensor itself is $180, but it's buried deep in the engine. They have to remove the exhaust manifold to get to the sensor, which is a lot of labor. Total cost including parts and labor - $800. They also suggested that continuing to drive it without repairing it could damage the engine.

Would appreciate anyone's comment on this, including their diagnosis, the cost of repair, and the risk of possible engine damage if I defer doing the repair - truth or fiction?

Driving around in the bypass mode should not do any damage, the engine is retarding timing and bypassing boost. I had the same problem for months before I changed the knock sensor, which cured the problem. The part is 142 bucks at Xterraparts.com, but you need to replace all of the intake manifold gaskets as well, I believe there were 4 of them. You also have to drain the coolant. I think it took me 6-7 hours.

Have a look here: http://www.supermotors.net/vehicles/registry/15556/52330

I took a picture of it while I had mine apart. It is in the valley under the intake manifold.

If it were me I'd mount a new one in a more accessable place and rewire the harness to it.

so i guess you wouldnt have to take the exhaust manifold off then?
so is that what happened to you k1w1t1m?
how many gaskets did you have to replace
great pictures though

Actually, to replace the knock sensor, it is five gaskets. One for the throttle body, the supercharger gasket, the intake collector gasket and the two intake manifold gaskets.

When this sensor fails, does it throw up an error code?

no. the knock sensor shows no code. if you have a boost/vacuum gauge you'd see no boost. thats how I knew and the fact it had no power.

HEY frontier sorry to be off topic here but what vacuum line exactly did you use for the gauge

The knock sensor will throw codes, mine keeps coming up P0325. However this does not turn on the SES light. It is also a 1 trip deal which I think means that it resets after the ignition is turned off.

The pictures are from last week when I replaced my drivers side headgasket. Definitely not a fun job. Mine is not a SC and I did it on the cheap so the gaskets I used were exhaust manifold gasket, 2 headgaskets (I damaged one...aaarrrhh), 2 lower intake gaskets and an upper intake gasket. The worst part of the job is getting to the fasteners etc for the stuff at the back of the engine. When you have big hands like I do getting to some of that stuff takes a real effort and some ingenuity.

All: I have a 2002 SC which also exhibits the 'NO POWER" symtoms after warmed up. I plumbed in a boost vac gauge and confirmed that upon startup, I get 7 PSI easy and after warmup only 2...the bypass is obviously on. I want to change the knock sensor and was looking for anyone who may have swapped in a maxima one with the harness to chime in and recommend a good place to mount the new sensor. Thanks to all in advance

What brand gauge did you use and where did you mount it? Thanks

Ahhhhhh, not a SC power loss thread again!! haha Happened to me too, still does on cold days even after getting the knock sensor replaced. It doesn't do it on warm days so I've learned to live with it. Two dealerships basically blew me off. One said it was fine-they redlined it until the auto fuel shut off came on, the other-told me it was because my bigger tires. :rolleyes: Ummm, fuck off? Here's a link to a thread in the "Problems and Annoyances" section- LINK

my gauges(day)- LINK

my gauges(night)- LINK

Bought the gauge pod here- LINK

Awesome! Thanks BigE515!

I see you have 2 gauges. Obviously one is the boost gauge, but what is the other?
Did you run your wires thru an existing opening or did you have to drill one?

The other is oil pressure. The hoses come in thru the firewall, there's a hole there already

might want to x-ref the knock sensor part #'s it looks very familiar to the ones they use across the years on many cars. some are cheaper for no reason at all.

When the hell is Nissan going to do a recall on the damn knock sensors??? I'm getting sick of seeing this problem on here and Nissan does nothing about it. Any ideas as to who we can talk to?