PCM Diagnostics & Tuning HP Tuners | Holley | Diablo

Not your same knock sensor thread.

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Old Apr 20, 2015 | 11:05 PM
  #1  
uscav82's Avatar
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From: 15 Mins outside Boston
Default Not your same knock sensor thread.

So I've spend a bit of time searching to see what I may have missed.

Even while shaking the harness in all areas I have been unable to detect a short to ground or a short to any other circuit in the entire engine harness. (No I didnt stab the wiring before anybody asks).

Even while rough housing the harness I dont see any change in the ohm values from pcm connector to ground showing both sensors at 100k Ohms.

History 2 years ago I replaced both sensors and the harness. Maybe 5k miles put on since then tops. Pulled it out of the garage this week and popped a code.

Replaced both sensors again, left the harness as there was no corrosion or damage to be found unlike the first time 2 years ago. I dont believe in Magic, and unless its an intermittent issue I hate throwing parts at things.

Now instead of Sensor 2 throwing a fit, its sensor 1. I cant imagine I damaged the harness on install, I taped it down so it could not move.

The only thing that I can think of is I pulled the battery over the winter. The pcm would have gone threw the relearn procedure for the minimum knock signal again. Maybe for some reason its learning a higher value than it should and then throws the code when it drops down.

Anything I may have missed here.

Oh yea, they are torqued properly assuming alldata is correct at 15 ft lbs.
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Old Apr 21, 2015 | 12:57 AM
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I'm thinking I'm going to order a fresh harness as well as a pigtail for the engine harness side. I'm going to clip the pigtail of this harness and solder it to the new one, snap it into the new pigtail and have a backup circuit in the event there is a ghost in the engine harness. That way I dont have to pull this g damn manifold again and if its all good I'll have a second pigtail hanging out if I ever need it.

Does anybody know what it takes to wipe the learned values in the pcm for the minimum knock sensor input. I pulled the battery for a little bit and the code came back so fast there is no way it did a relearn.
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Old Apr 21, 2015 | 08:13 AM
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Did you torque the sensors to the correct value ? I know that can cause issues. I always replace the harness under the manifold it usually gets pretty beat up from the heat. Instead of pulling the battery get a code scanner so you can see the freeze frame of whats going on when the code is being thrown. You can get a bluetooth code scanner for like $15 on amazon and torque is like a $5 app.
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