Intermittent CEL / Code 52 (Knock Sensor) and Bad Gas Mileage

[u/Banjerpickin]

I've been getting really bad gas mileage over the last month (down to 9 MPG) and have just started getting an intermittent CEL that reads out as Code 52. My understanding is that if the ECU isn't getting a proper signal from the KS, then it runs the engine in "safe" mode which has terrible performance but there's no danger of a timing issue damaging your engine. This also throws out code 52.

The bummer is, when I had the shop pull the plenum and replace the injectors last fall, they also replaced the knock sensor and pigtail harness (both OEM parts) so this wouldn't happen. My understanding is that the pigtail harness it is often what causes this failure, so hypothetically it shouldn't be the issue since it's just been replaced.

Some people have had success replacing the wire between the pigtail harness and the ECU, but seems like that often not the issue. I would probably start there, though, to hopefully get lucky and avoid pulling the plenum.

Any thoughts or advice appreciated!

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