Help please.

I have a 2002 z28 that is throwing this code.

-I replaced both knock sensors and the harness- code come back after about a day of driving

-I pulled the intake back off, checked each sensor (both good) checked the harness for pinching (all good) and traced the harness all the way out looking for splits/cracks and cleaned the connector- code come back after about a day of driving

-Replaced PCM- code come back after about a day of driving

As far as I know, I have tried everything. What do I do next? Surely the car can't just decide to throw this code and there is nothing I can do about it...

Any help/suggestions would be appreciated. Thanks!

PS. I did several searches, but didn't see any cases where a person has been this far into troubleshooting and still have the problem.

 

Maybe you torqued it wrong or not making good ground connection.

 

agreed with umair, wrong torque on sensor might throw a code. did you buy delco sensor or cheap store brand? this will also make a difference.

 

Hey, thanks for responding.

I did go with the AC Delco sensors just to avoid problems (ironic) and I torqued the sensors to spec. I guess I should have mentioned those details.

umair, if I wasn't making a good ground connection, would the sensors still function? Because they are functioning normally when I test them.

 

I filled up with some extremely poor quality fuel before going to the track last Friday. The car was down over 6mph in the 1/4 and I didn't know why (no scanner with me).

The pcm had that code stored for bank 1 knock sensor low voltage. I cleared it and went for a drive, car was getting over 9* KR at half throttle, I immediately filled up the tank with some better fuel.

The car started running better and the code has not come back.

 

Interesting. I only use 93 octane which is the best available in my area. I always get gas at the same place but I can't gurantee the quality.

I do have a station in the area that guarantees ethanol free. I think I'll fill up there next time just to cover that base.

 

It should be very apparent. Make sure you use a good name brand fuel if possible (Shell, Chevron, Phillips) to help reduce risk.

If you have a scan tool you should be able to see if it is pulling timing

 

Can going to a name brand station really make a difference? I get gas at Ingles, I figured it was all the same...

I have a friend with a scan tool; I will take the car by there and see if it's pulling timing. If it is pulling timing; what would that tell me as far as a next course of action?

 

Lucky for me I burned pretty much all of the bad gas on my way home from the track so I just topped off with as much Shell 91 as I could get in the tank.

If the car runs better after that and the code doesn't come back I would change your fuel filter and run some injector cleaner through the next couple tanks of fuel.


Granted if your problem is still sensor related or wiring related it won't help, but its low cost and good practice anyway. Just throwing out a suggestion based on my recent experience.

 

The PCM has too see the error twice before it throws a code. It takes a couple cycles of the ignition to get the code to come back. Mine was coming on so I turned the codes off in the tune until I get a chance to troubleshoot.

 

had same problem with my silverado. turned out being defective new gm knock sensor.

 

How did you determine it was defective? Both mine are testing at consistent ohms.

Could they be defective but still read adequate voltage?

 

Well I spoke too soon, my code is back. Looks like on top of the bad fuel I also have a defective sensor.

 

That's ironic, because I just filled up this morning at Sunoco and the whole time I was thinking- "I hope the light goes off... I hope the light goes off..."

I hope it's an easy fix for you.

 

this thread might interest both of us

https://ls1tech.com/forums/pcm-diagn...l#post16812405

 

Thanks for this!

I decided to start from the beginning over last weekend and follow this troubleshooting guide. I pulled the intake off and as I removed the front knock sensor, I could tell that the internal part was basically freewheeling in the casing. So even though it was reading as giving off normal ohms, the unit had obviously failed.

Either the part was faulty or I did overtighten initially. I don't think it was me though, because I put both sensors in at one time and the other is fine.

So anyway, I changed the bad one and haven't had a problem since.

Lesson: If a problem can be traced back to a specific mechanical component, don't just try to troubleshoot from an electronic side.

Thank everybody for chiming in!

 

Hope I'm as lucky when I replace mine...maybe thursday

 

Picked up a Delphi sensor from Advance. The code was gone still since I last cleared codes a week ago but I changed it anyway. I'm back to speculation it was in fact due to very poor fuel quality though.

Had the intake off the car in right at 7 minutes...I'm sure anyone with an fbody would have been pissed to see that haha

 

Im still having problems with the code. If you go to the thread i have updated what i have found. I still puzzled.

Ok so after doing everything above I replaced the wiring going to the PCM from the Knock sensor Pigtail. This did not fix the problem

I then changed the PCM and downloaded the program and 2 miles down the road the code came back.

When i got the car home i disconnected the pigtail that is located behind the intake and measured the millivolts and resistance while running. The millivolts on the rear sensor fluctuated from 70mv-100mv. The resistance on the rear fluctuated from 30k ohms to 60kohms to Overload. This was checked while the car was running.

The front sensor was the the same with the millivolts as the rear, fluctuated from 70mv to 100 mv. The resistance while the car was running was 15kohms to 50kohms but was going overload alot more than the rear.

I turned the car off and the resistance on both sensors were around 99k ohms.

This has me puzzled. Any opinions are appriciated. I have videos of the readings if anyone is interested in seeing them.

 

^
Your problem sounds very similar to mine and your checks seem to be drawing the same conclusions.

In my case, even though both sensors showed a consistent reading, once I took the intake back off and physically checked the sensors again, I could tell that the front one was bad because the internal component was too loose. If you haven't done this yet, I wouldn't rule it out.