johnblagg

Just what I have seen with my 1992 es300 and both knock sensors being totaly unhooked is that the knock sensors do not cause the ecu to go into limp mode what so ever !

The wiring harness going to mine was so old and insulation cracked if you attemped to bend them at all and wold fall of the wire.since it was obviously causing the codes I cut both lines into and tried every thing I could find online in the line if a bypass circuit ...one cure actually worked half assed and I could eleminate the code for one sensor or the other with usb cable replacing the bad wiring and hooked to radio shack pizeo electric buzzer elements.....

Since I knew the plugs were bad and had to have new belts as well because of the same issue and aged parts that the previous owner did not have replaced when he had a head gasket replaced "BIG WHAT THE HELL WAS HE THINKING GOES HERE" I put it in the shop to have new belts and a compleate tune up new plugs, wires,distributor cap and rotor bug because I had a miss on #3 new plug wires cured the miss and she runs sweet now even whit the code for both sensors still triggering the check engine light .

I also discovered that the miss on number three causes the car to shudder at 55 especially in overdrive ...if I disable over drive it would resovle some but not totaly so a miss will make you wonder if teh tranny is acting up too folks if your thinking you have a tranny issue and its a shudder at 55 to 65 try a tune up first .....

Anyways back to knock sensors after the tune up I just conneted the knock sensor wire to the shield /ground wire to make the ecu see a shorted sensor on both and am driving her this way untill I can get her in the shop again and have new sensors installed ....If I am going to own a lexus she will run correctly and not throw codes even if they dont seem to effect her operation .Mean while with sensors sending a signal that they are crap and non functional thsi car runs fine and overdrive works perfect so knock sensor codes evidently do not trigger limp mode or disable overdrive on a 1992 lexus es300 .....I read over and over on this forum that they do but from my experiance over the last month they do not have any effect that I can see at all...they prabably do affect engine preformance and fuel economy but they do not cause limp mode or overdrive to stop functioning.

tomf

Oh contrar. My Bank 2 knock sensor just went bad. After driving it for about 30 minutes after clearing the MIL, my ES300 would go into limp mode. No power on acceleration. Before I had this problem I did not know what people meant when they said limp mode. I do now. BTW after replacing my knock sensor my es does not go into limp mode nor does the MIL illuminate.

johnblagg

hmmmm all I can tell you is mine has not done so and both knock sensors are throwing the code and I have unhooked them and simply shorted the sensor wires to the sheild wire untill I can get new ones installed.

LOL if this is limp mode she is going to get incredible milage whet they are fixed....I get 23 mpg now and overdive works perfectly

tfifeco

i know this thread is a little old but i can say that i just had a buddy come over and help me check my codes due to the CHeck Engine light coming on. Found it throwing Code 55, Right Bank Knock sensor. SO i guess i need to change mine ...BUT, the car runs great and has been running great, NO LIMP MODE HERE EITHER. Only problem i am having is Cold start problems and idles a little low, but i thnk that may be a dirty IAGV. Anyways, just wanted to throw out that My knock sensor appears to be bad but doesnt go in limp mode either, FWIW