99jewel

'99 RX300 reading problem with knock sensor & MAF. CEL on for quite some time, and car won't shift into OD (high gear).

Seems like I recall reading a post recently that mentioned the wiring harness is more apt to be the problem than the actual knock sensor. There was a DIY step-by-step description of a method to check wiring harness without having to dismantle intake manifold, and thus negate the need to buy new sensors (which are not cheap). Can someone please locate the post I am referring to?

Also, where is cheapest place to buy the sensors & wiring harness. I have searched for the harness, read that it was replaced with a newer version, but cannot locate any other info. on it. Thanks!

bob2200

Let me be the first to ask the question: Have you checked for OBDII diagnostic codes, and if any, what are they?

99jewel

Bob: It's been a while, but I'm certain one of the codes was 0330. Believe the other one was 0171 which showed up many months before the 0330. Have terrible knocking, no OD, and CEL on for a year or so. I cleaned the MAF when 0171 first appeared, and it seemed to do the trick for a while. Then, when I started having shift problems, the OBDII showed both codes. Looks like sensors are going to run around $125 each, but I can't seem to find the wiring harness. Seems like I read where the harness changed with the sensors several years ago.

thomas1

Here it is:
http://us.lexusownersclub.com/forums...howtopic=41266

99jewel

thomas1: appreciate the link, but I was already familiar with it. My question is: Is there a way to check to see if wiring is bad, not the sensor itself, before I start tearing the manifold off? I found a similar article on a Toyota forum, and it may be the one I read before (as opposed to a ClubLexus forum). Does anybody know how to test the wiring before I start repairs? Thanks!

Lexmex

I double checked with the manual, but the only way seems to be to check the sensor itself with an ohmmeter.

99jewel

And I guess that means I need to pull the sensor to check with ohmmeter. Oh well, I appreciate all of the help dudes- time to GIT-R-DONE!!!

Lil4X

Back in the day there was a shade-tree procedure that involved lightly tapping on the engine block with a small ball-peen hammer near the knock sensor with the engine idling. A good sensor would hear this simulated detonation and dutifully retard the spark, slowing the engine a hundred rpm or so briefly. It would sometimes sound like a stumble in the idle as when the tapping stopped the engine should return to its pre-mapped advance curve. That's one trick I haven't tried in 20 years or so, but it might be worth checking to see if you can fool a modern ECM with it.

Lexmex

My uncle in Ohio used to do this trick, that might be worth a try.