1991 Subaru Legacy non-turbo indicates knock sensor trouble code

[vhauri]

I have a 1991 Legacy sedan with around 116,000 miles on it, and the
check engine light recently came on. After hooking up the test
connector, I was able to make the light flash DTC 22 at me, indicating,
according to the repair manual, a problem with the knock sensor that
could result in the car defaulting to 'fail-safe' timing mode. Now, it
seems pretty clear that the first step would be to replace the knock
sensor, but I don't really have time to do that this week, and it would
be nice to keep the car in service for short trips to the store, etc.
So, my question here is a three-parter:
1) Is there anything I should try before yanking the knock sensor?
2) Is it safe to drive?
3) This can't be an indication of engine knock, right? Or would this
trouble code also manifest because of the beginnings of an engine
knock?

I appreciate any ideas anyone might have....

-V

 

[Carl 1 Lucky Texan]

I have a 1991 Legacy sedan with around 116,000 miles on it, and the
check engine light recently came on. After hooking up the test
connector, I was able to make the light flash DTC 22 at me, indicating,
according to the repair manual, a problem with the knock sensor that
could result in the car defaulting to 'fail-safe' timing mode. Now, it
seems pretty clear that the first step would be to replace the knock
sensor, but I don't really have time to do that this week, and it would
be nice to keep the car in service for short trips to the store, etc.
So, my question here is a three-parter:
1) Is there anything I should try before yanking the knock sensor?
2) Is it safe to drive?
3) This can't be an indication of engine knock, right? Or would this
trouble code also manifest because of the beginnings of an engine
knock?

I appreciate any ideas anyone might have....

-V

I THINK you may only suffer decreased performance and MAYBE also
slightly worse fuel economy. If you clear the code by disconnecting the
neg. term. of the batt., step on the brake pedal, wait for - say -
20-30, reconnect; and the code immediately is set again - yeah, it's
likely a real code for a bad knock sensor. If it doesn't come back, it
could've been some kind of fluke I guess. Do check for corroded ground
and wiring/connector problems in case re-seating a connector or
something fixes it.

Carl

 

[johninKY]

Carl is correct. Clear the code. Remove sensor and check for corrosion.
If the code returns then replace the sensor. No problem driving it until
repaired. The ECU will just retard the timing enough that you don't have
a knock condition.

 

[vhauri]

Wow, thanks for the quick replies! I noticed the bulletin for this car
about potentially corroded wires on the knock sensor, so your advice
about cleaning it off first sounds like a good idea (and cheaper than a
new sensor, which I like alot).

-Vasken