knock sensor low input

**BruceLee** · 01-23-2008, 05:50 AM

Ok heres the deal...I have been getting a ses code for front and rear ks low input. I replaced both knock sensors and the harness, thinking it would take care of the problem. However after driving the car for a few miles, it has thrown the same codes. What else should I look for, to cause this problem?

thanks

**BruceLee** · 01-23-2008, 08:41 AM

anyone?

**autotrix** · 01-24-2008, 09:12 AM

Trace wires back to PCM for more connectors and or bad connections. Check if there is a reference voltage, if so, check the voltage coming from the PCM,at the PCM and at each individual sensor.

**BruceLee** · 01-24-2008, 10:15 AM

Originally Posted by autotrix

Trace wires back to PCM for more connectors and or bad connections. Check if there is a reference voltage, if so, check the voltage coming from the PCM,at the PCM and at each individual sensor.

thanks for the info..will try this out asap

**2001NBMZ28** · 01-24-2008, 10:54 AM

You can also OHM the sensor side of the connector behind the intake to see if it's on the sensor/harness side. Visit gearchatter.com and look up the codes for your year, it'll give you the value(s).

**BruceLee** · 01-30-2008, 04:46 AM

so i had my mechanic check the car out for me. He said that all of the sensors and connections are working properly to the pcm, and reccomended that I swap out the pcm. Has anyone else had there pcm go bad?

**autotrix** · 01-30-2008, 05:05 AM

Sure they go bad, and its usually stupid little things that fail that are controlled by it. If you trust his ability I would trust his diagnosis.

**99DROPTOPZ** · 01-30-2008, 07:31 AM

When you replaced the knock sensors was there any corrosion around them? I just had my intake swapped because my knock sensors were bad and my mechanic said he sealed the the rubber plugs with silicone so nothing can get in there and cause corrosion to the knock sensors again. Look in to this before swapping your PCM.

**BruceLee** · 01-30-2008, 09:49 AM

Originally Posted by autotrix

Sure they go bad, and its usually stupid little things that fail that are controlled by it. If you trust his ability I would trust his diagnosis.

I trust him with this type of stuff as he was a gmtech for the last ten years before opening his shop..I just like to have a second opinion tho

**BruceLee** · 01-30-2008, 09:50 AM

Originally Posted by 99DROPTOPZ

When you replaced the knock sensors was there any corrosion around them? I just had my intake swapped because my knock sensors were bad and my mechanic said he sealed the the rubber plugs with silicone so nothing can get in there and cause corrosion to the knock sensors again. Look in to this before swapping your PCM.

there was not really any corrosion but there was some oil on them. Mine were sealed with silicone also

**2001NBMZ28** · 01-30-2008, 09:56 AM

Don't know what year/mileage you have, but thought I'd mention the PCM is covered under the federal emissions warranty for 8yrs/80K - at least it was in 2001 when I bought my car.

**99DROPTOPZ** · 01-30-2008, 09:57 AM

At least you have them sealed up now. I'd be suprised if its the PCM I'm curious so keep us updated. Good luck!

**konigandy6** · 01-30-2008, 03:23 PM

Originally Posted by BruceLee

Ok heres the deal...I have been getting a ses code for front and rear ks low input. I replaced both knock sensors and the harness, thinking it would take care of the problem. However after driving the car for a few miles, it has thrown the same codes. What else should I look for, to cause this problem?

thanks

You may have a couple simple issues going on... GM constantly comes out with software updates for every vehicle to clear the computers of false codes that could come up. I see it every day where I work. Or you just may have some bad parts put on. I'm not 100% sure but aren't the KS located under the intake manifold? I know thats where they were on my brothers HD pickup.

My suggestion would be to take it to the dealership and pay the 1 hour diag fee to see what they say. Ask your adviser to make sure the tech checks for any software updates for your vehicle. If that is not the case, you may be looking at a PCM swap. Thats just my opinion, don't shoot me!! lol