Anyone with knock sensor failure information (mileage) for LS400 model years:

1990-1994
1995-1997
1998-2000

Online information suggests knock sensors degrade over time before triggering a code..
Not easy to access or easy to replace, but failure info useful to those replacing starters.

It appears the 2004 LS400 employed an improved ring shaped sensor, instead of earlier threaded knock type,.however it does not appear to be a plug and play proposition

Thank you

 

I don't have exact mileage, but I had one start throwing codes at around 130k, give or take. That's for a 98. I drove it for two or three years clearing the code, which would pop up once or twice a week. But having the timing retarded whenever the code popped up was really annoying, so I changed them both out. Twice. The first time with counterfeit parts, which resulted in knock sensor codes nearly every drive. You won't find a deal on knock sensors. If you find a deal, you made a mistake. If you're changing out your starter, it would be a no-brainer to change the knock sensors, if they weren't so ridiculously expensive. And they are. And you have to use factory knock sensors or you'll do the job twice. So you have to weigh the cost and ask yourself if it's worth throwing $400 at knock sensors when you're changing your starter.

 

Numerous reported, yet not fully resolved low idle issues on 1998 - 2000 LS400's..numerous contributing factors.

Am wondering if low idle on fully warm, well-maintained engine is symptomatic of diminishing capacity, but not outright failure,
of knock sensor?
OR baked knock sensor wiring in engine valley...
Our Denso knock sensors contain resistors in series?

 

I can answer only this question.
Most of them have a parallel resistor of a few to several hundreds K ohms. The purposes to add a resistor is to do a damping and to make it possible to check the condition of cable's open/short. The sensor itself is a ceramic resonator and it is not conductive. In order to check the cable, a paralleled resistor is needed.

 

Hi Yamae;

Unlike electrolytic capacitors, there appears scant information online regarding life expectancy of internal combustion engine knock sensors, or whether there is degradation over time or simply critical failure..

There appears a resistor in the knock sensor in parrallel (which as depicted in a generic diagram to be in series) so it is unclear whether thevresistive element value is subject to stray..or whether it is even relevant.

Precursory review online suggest sensor engine codes are triggered due to knock sensor wiring harness (rodents or high heat in engine valley degrades the wiring and makes connector shells brittle) or fluid immersing the sensors in the engine valley from engine coolant or pressure washing the engine...

Based on the number of posts, it appears knock sensor failure is more common on LS430... or perhaps I read it more there because the LS430 is intolerant of aftermarket knock sensors and a lot of counterfeit parts on Ebay and Amazon.

Someone has life test data...but who?

 

Do you think I should replace the knock sensor if I am not seeing any codes pop up? I will be working on the starter and I’m considering also changing the two knock sensors, but this will add $300 to the bill.

89615-12040
This is the correct part number for the knock sensor for 1999 LS400, right?

 

Mine were exposed when I did the starter back in April. I left them alone. However, I did replace the brittle and broken off covering on the wire harness.

 

Where did you get that wiring harness?

 

Yes.

Replacing them or not is a tough call. If someone knows why they fail in some cars and not others I'd like to know, mileage doesn't seem like a good indicator.

 

It's the original harness. The factory wire covering gets brittle from heat and breaks off, leaving the wire bare.

I just covered the wire with is:

https://www.summitracing.com/search/...raid-wire-wrap

 

It’s really just a question of how much is your time worth.
Once you remove the intake to access the parts you’ll know.
If it took 3 hours to remove the intake it might be worth the gamble, if it took 6 maybe not…