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Discussion Starter #1
I had the timing belt changed on my 2002 Nissan Frontier SC last week as preventive maintenance (100,000 kms). Ever since then, the "Service Engine Soon" light has been on solid. The dealer says that it is the knock sensor that needs to be replaced.

I know nothing about vehicles, but this seems very coincidental - everything was fine until I had the timing belt replace and the minute that is done another part goes? I suppose it could happen, but any insight into if changing the timing belt could cause an issue with the knock sensor would be appreciated or is this truely coincidence? Thanks.
 

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The knock sensor will NOT set a check engine light!!
They need to scan the codes ,and go from there.

The knock sensor will set a code in the computer ,but no light.
They probably left something disconnected after doing the T belt.

How is the truck performing?
They dont affect performance on the n/a engines ,but they will pull alot of boost on the S/C engines.
 

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More than likely they scanned the codes while it was in for service, and the knock sensor code came up (very common). Now they're attributing the SES light to that code.

Go to a parts store, have the codes scanned and let us know what they are. It's very possible these new codes are caused by something they left disconnected after reassembly.

Those Nissan techs are often no smarter than the morons behind an Autozone parts counter. I called several service departments here to get an estimate on the timing belt replacement for my truck ('01 SC), and two of them told me the VG33ER has a timing chain. They were good for a laugh and nothing else.

Ozias, how much did the T-belt replacement cost you?
 

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Discussion Starter #4
The timing belt cost me $700, the knock sensor $900.

The light continues to be on. They now are saying it is the O2 sensor(s). They have changed one of these sensors, they tell me there is 4 and that they may all need changed. Apparently, I am told by the dealer, that when the knock sensor goes, the O2 sensors over compensate and are commonly damaged which is likely what happened to me. They can't tell me if all 4 sensors are gone, but rather, replace one at a time and see if the light goes out?

Again, I know NOTHING about vehicles. The truck is running well, in fact, I believe it is running better. The pickup seems improved since the knock sensor was replaced, but I have no actual proof of that other than the way the truck "feels".

I know I am getting hosed. I don't know of any parts stores in Canada that will scan.....
 

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You have a choice. You can keep shelling out dollars to the dealer (who is taking you for a ride) or you can get smart on your vehicle. If you cannot trust the dealer you need to find a shop you can trust.

If you decide to get smart on the vehicle you can purchase a code scanner for about $100 (US) or less. There are a number of sites on the internet that will tell you what the code is and the probable causes.

The dealer's line about the O2 sensors overcompensating for the knock sensor and being damaged is (excuse my language) crap. I would get a scanner and reset the light (also zeros previous codes). See if the light gets set again. Read the codes if the light is set. Tell the forum what the code(s) are, e.g. P0xxx, and we can suggest a course of action.

Steve
 

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Your observation of increased power after knock sensor replacement seems spot on. Nissan is very conservative with engine management on the supercharged vehicles. If the knock sensor goes, engine goes into limp mode and maintains a maximum of 3psi boost, rather than the normal 7-8.

I wouldn't trust any dealer who advises you to replace four oxygen sensors. The knock sensor has little to do with the O2 sensor. Sure the mixture would be richer to compensate for engine knock, but that's part of the ECU design-- The 02 sensor couldn't care less.

An alternative to buying a code scanner is to take your truck to Autozone or a local parts store. Many of these places will scan trouble codes for free.
 
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