Knock sensors troubleshooting

Michael31 · January 20, 2020

I’m driving a 2001 GMC Sierra 2500HD 6.0L. I had codes P0332 & P0327 knock sensors. Low voltage output. So I replaced the knock sensors & intake manifold gaskets, and cleared the codes. When driving down the highway about 40 mph or more the check engine light appeared again. Again I have P0332 & P0327! Along with that I also have P0: 171, 172, 174, 175, 507, and 101. I found a vacuum leak to fix the P0507. If I drive slow ( as in plowing snow ) there’s no issues. If I go on the highway all the codes come back ( except the P0507 ) I’ve replaced the MAF last year with no issues until now. I searched for leaks using smoke and only found 1 that corrected the P0507 code. I’ve torqued the knock sensors to 15 ft. Lbs. and the intake using a 2 step torque sequence and pattern. I just cleared the codes again for myself to recheck. No codes yet but I haven’t gone down the highway since. ?? Any ideas??

riverbanks · January 20, 2020

When it's lean,that can throw a k.s. code,I would clean the MAF

Michael31 · January 20, 2020

Thank you George.

I cleaned the MAF sensor and all the codes disappeared. You are amazing!

About 8 miles and two hills later my "service engine soon" light came back on? But only the 332, 327,172, and 175. I'm making some headway.

I'm still confused about the knock sensors? ( they are new )Why is there no code then after driving highway speeds they shortly return???

I mean it! Thank You George.

CamGTP · January 20, 2020

Did you replace the harness as well for the knock sensors?

How is your fuel pressure? Low fuel pressure can make lean codes happen.

riverbanks · January 20, 2020

Lol,amazing,I read that off of a fortune cookie,so harness?,and what brand sensors, including MAF?

Michael31 · January 21, 2020

Carbole Knock Sensor Harness Pair Kit is the sensors and harness I used. They have a lifetime warranty is why I used them. The MAF I would have to check on? I replaced that about 2 years ago.

"How is the fuel pressure" A new Herko fuel pump last summer and a new check valve. Pushing about 45 - 50 PSI. I also replaced the fuel pressure regulator at the same time.

Edited January 21, 2020 by Michael31