1991 Toyota 3.0 V-6 Knock Sensor data

I just had to troubleshoot and error code 52 on my truck and found
the following information I thought I would share. The knock sensor
can be tested by using a digital multi meter like a fluke 83 (cheaper
models do not detect the knock sensor signal). Put the meter on AC
voltage with autoranging. Put the negative lead of the meter on the
engine block or a good metal ground on the engine and put the positive
lead on the knock sensor contact. By tapping on the block lightly with
a socket extension you will see a voltage detection and in the case of
the Fluke 83 there is a bar graph indictation as well. If you want to
check the sensor and wire without taking the intake off first, the
pigtail connector is located next to the middle fuel injector connector
on the driver's side of the engine, it has two contacts, one is the
center conductor to the sensor, the other one is to the noise shield
and won't have a signal on it.
In my case it turned out that the knock sensor pigtail wire had
opened, the $13.00 dollar wire from the dealer was a lot easier to take
than the Knock sensor at $175.00 from the dealer or around $145.00 for
a Borg Warner model from Checker auto.

You hit it head on Sgt. Most knock sensor codes are wiring related, one
reason being their location - often between v-banks and near exhaust.
Since the output from the sensor is AC, the wires must stay sheilded. Once
the shielding breaks down from heat and vibration, the signal degrades and
the computer can no longer read sensor input. The piezo-electric units
themselves rarely fail.
Nice job on the diagnosis.