Knock Sensor questions
 

Stored codes from my teal SVX:
#22 knock sensor right
#28 knock sensor left
#37 oxygen sensor left

The knock sensor code explanation reads, "Abnormal voltage in knock sensor monitor circuit."

Questions:
1) Could some fault other than bad knock sensors affect the "monitor circuit"?
2) What's the likelihood that both knock sensors could fail pretty much simultaneously?

CEL is intermittent and rarely on for 2-3 minutes of a 15-minute drive. Car runs fine. Fuel economy could be just a tad off.

Thanks in advance.
dcb

Re: Knock Sensor questions
 

Did all 3 codes appear at the same time?

Some people have found that their timing belt was out of alignment which caused similar codes.

I've seen knock sensors with the plastic shells broken but not throw errors. Have you done anything under the hood recently?

Re: Knock Sensor questions
 

First got the CEL in March; stayed on just a couple of minutes near the end of a 100+ mile highway drive. Very intermittent since then but increasing in frequency. Seems more prevalent in stop-and-go driving than at cruise. Finally got around to checking for codes yesterday. First time I've had cause to pull codes from this car.

No major work lately. 57,000 miles on the timing belt. No knocking or missing or stumbling nor other obvious misbehavior to suggest jumped time.

Thanks,
dcb

Re: Knock Sensor questions
 

Almost sounds like an electrical/computer problem.

Re: Knock Sensor questions
 

It wouldn't hurt to change them..they are not expensive, just maybe a bit time consuming. I found that my sensors both had cracked housings but they did not throw any codes. The connectors though were caked and sitting in oil due to standing oil under the intake plenum on my vehicle...perhaps the connections may be suspect?

Re: Knock Sensor questions
 

162k. I'd say it's time.

Re: Knock Sensor questions
 

No doubt. I just thought it odd that both would (apparently) go bad within a three month span and wondered if something else might be going on. On second thought, maybe it makes perfect sense, after 20 years of baking atop that engine.

dcb

Re: Knock Sensor questions
 

Let us know how it goes. Given that you have always been correct in the advice you have given me, I'm assuming you will get it solved quickly.

Re: Knock Sensor questions
 

All of those 3 connections use the same harness I believe..you could have a bad wire somewhere in there. Why isn't the 2nd O2 sensor faulting I wonder...it's on the same harness as well right?

Re: Knock Sensor questions
 

Can't say about the harness; definitely getting beyond my line of country there. The next course of action will be to disconnect the battery for a spell and jiggle some wires, maybe see what goes where.

Got a flicker of a check engine light in the sliver car years ago, read a code 37, cleared it, and haven't seen the CEL since.

Thanks to all for the input.
dcb

Re: Knock Sensor questions
 

IIRC, the knock sensor is on the engine harness while the o2 sensors are part of the body harness. Just replace the knock sensors, reset the codes and I bet it takes away the o2 sensor code. The knock sensors force the ECU to adjust timing which will mean its not running ideally.