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Comes on usually when accelerating and cruising, and goes off when stopping or idling.

Is that a normal behavior for a CEL if there's a problem with the knock sensor (checked codes - it throws up 05), or should it stay on continuously?

Normal.. anytime I have had a code thrown while driving.. its intermittant. Comes on.. goes off.. comes back on later when it feels like it.. goes off.. etc.. Gotta like the simple codes like the knock sensor though.. easy to diagnose & replace.

Tunes67

Ah, alright. Thanks.

I don't hear any knocking, though. So I'm not sure if the sensor is doing anything or not... I'm guessing ECU would go into limp mode, no? Is it safe to drive a car in this condition? Obviously knocking is bad for the engine, but I need to drive and I won't be able to get a new sensor for a few days.

It might go into limp mode.. I am not sure what happens if the knock sensor fails completely.. havent had it happen to me. Hector here had his go bad and it seemed like he was still driving on it.. so I would think you'd be ok for a day or two if it doesnt seem like its running bad.

Tunes67

i had that happened to me, with the knock sensor, and i found out that one of the connector's wire was a lil lose, and it was making\not making contact while the motor was on load (vibration), i spliced both connectors and hotwired all , problem solved

yah i had the same problem wiht my o2, it would come on and off while driving. I found if i reved the engine just after it came on it would go away for a bit?

Tunes67 wrote:It might go into limp mode.. I am not sure what happens if the knock sensor fails completely.. havent had it happen to me. Hector here had his go bad and it seemed like he was still driving on it.. so I would think you'd be ok for a day or two if it doesnt seem like its running bad.

Tunes67

Yeh, it's running ok. I just drove it, and CEL didn't come on and it ran fine. Maybe the motor was still cold or something.

For knock sensor maybe a bad ground can cause it. Or a sensor waiting to fail. Worst thing that happens is that the ecu goes into limp mode. There are some rare ecus that dont have limp mode as per 1st probinator. Not sure if applies to the k8 program.


I had the ghost o2 sensor codes. I took outo2s cleaned them and the code never came back.

Huh. All the connections appear fine.

Actually the CEL is coming on less and less. Came on for like 10 seconds last night, and not at all today. Not sure if that's a good thing or not. As far as I'm aware, car problems don't fix themselves, so this is rather strange.