My 99 Legacy 2.2L has about 80K miles on it. Recently the Check Engine Light started coming on now and then, especially when the weather turns from "seasonal" for northern US to "freakishly warm", i,e. above 50 degrees.
I've removed and inspected the knock sensor visually, and detect no cracks or other obvious damage. I have traced out the wiring, and I know I need to do some electrical checks. Verify no grounds, or shorts in signal or shield wiring, nominal voltage 2.8 volts at ECU, and some where I read there is a resistance spec for the sensor itself, somewhere above 500 K ohms. Can anyone confirm that last?
Now, assuming all of that checks out, then I have to believe it's sensing an actual knock condition, right? I understand the ECU is supposed to ree tard (that's a filtered word? jeez) the ignition timing until it "stops knocking".
These knock sensors aren't cheap, so I really want to check everything I can before I blow the money on a new one.
Could it be I have carbon buildup in my cylinder head, causing increased compression? I tried using some injector cleaner in three consecutive tanks of gas, in case it was clogged injectors.
I have subscribed to the DIY online service manual but not much is said about troubleshooting this.
Off topic, but I'm finding that the electrical diagrams online have some odd inconsistencies, when "chasing wires" from one drawing to another.
I am in Denver, a mile above sea level, burning 85 octane gas as I always have in this vehicle. Engine operating temperature is normal. My ears detect no pinging or knock.
