Knock sensor bypass

**PON-TON** · 02-28-2011, 03:42 PM

Does anyone know a good procedure to temporarily bypass both knock sensors on a 2000 LS1? I searched around and got some LT1 specific info, then found something for the LS1 which involved cutting the two knock sensor leads from the PCM (#11 & #51), then wiring in a pair of 100K ohm resistors, one lead to PCM and one lead to ground. I did that,cleared my codes and after 20 minutes of driving I got knock sensor codes 327 and 332. So I'm thinking that procedure is flawed. I have been chasing a crappy no power/surging part-throttle situation that throws the sensor codes and the 300, random misfire code. Any help would be sincerely appreciate. Thanks!

**blackSS01** · 03-06-2011, 07:25 AM

Originally Posted by PON-TON

Does anyone know a good procedure to temporarily bypass both knock sensors on a 2000 LS1? I searched around and got some LT1 specific info, then found something for the LS1 which involved cutting the two knock sensor leads from the PCM (#11 & #51), then wiring in a pair of 100K ohm resistors, one lead to PCM and one lead to ground. I did that,cleared my codes and after 20 minutes of driving I got knock sensor codes 327 and 332. So I'm thinking that procedure is flawed. I have been chasing a crappy no power/surging part-throttle situation that throws the sensor codes and the 300, random misfire code. Any help would be sincerely appreciate. Thanks!

There is NO reason to bypass the knock sensors. If you do and shit goes south then BOOM....buh bye motor. I would get new knock sensors and fix what is causing your problem. That will solve your issue instead of messing with wiring and sensors that are not suppose to be messed with.

**Knight** · 03-06-2011, 08:12 AM

I agree with BlackSS01 - you'd be better off fixing the problem instead of trying to bypass it. It does sound like you have multiple problems though. I'd start with the knock sensors first, then check into the misfire by checking plugs, wires, coils, and related wiring. You could also clean the MAF with some CRC cleaner, that may help your power problem.

**blackSS01** · 03-06-2011, 08:42 AM

Could always do the full tune up type thing:

Plugs
Wires
Air Filter
Oil change
Fuel Filter
MAF cleaned
Clean Throttle Body

That will eliminate some areas there could be problems. Just don't be getting rid of the two most important sensors (IMO) If the knock sensors are throwing codes they need to be replaced. If they are kicking in, they are saving your motor.

**Firebirdjones** · 03-06-2011, 09:34 AM

Unless you are confident in your tuning ability, never run piss poor gas in the car, then I'd keep the knock sensors working, at least to some degree.

Sounds like you need to replace them, pretty common with these LS engines it seems.

I've decensitized mine to some degree, only because I'm confident that I have a solid tune in the car, I always run high test at the pump, and I keep everything up to snuff. There are things I didn't care for in the knock tables.

**PON-TON** · 03-06-2011, 07:39 PM

Thanks for all the advice, lots of good info. I was trying to quickly eliminate the knock sensors to help tracking down my no power/surging part-throttle situation. I did additional research which pretty much confirmed the "resistor trick" would never work anyway, as the PCM is looking for a .5-1 volt pulse, not simply resistance. Anyway, I replaced both knock sensors and measured 99-100 k ohm resistance at the PCM confirming proper wiring integrity. The knocker sensor codes are now gone, but the random misfire 0300 remains as does the low power/surge thing. I'll proceed sorting out the misfire now that the knock sensors have been eliminated fro the equation. Thanks again.

**Serpico327** · 07-22-2016, 09:23 PM

Hello, after reading a couple of threads in this forum, which are pretty good regarding sensor problems, I did ohm my new harness and it read 0 OHMs on both ends. Is'nt it required to ohm at O? does it not mean that the wire is solid and not broken in any place? It mentions on one of the answers, that the harness is grounded, therefore you get both PO327 & PO332 codes showing as the trouble codes.

**pajeff02** · 07-23-2016, 06:53 AM

I would have to look in the manual but I believe you are correct. A continuity test will tell you that there are no breaks in the wire.

**Serpico327** · 07-23-2016, 01:56 PM

Thanks. I have always ohmed wires before installation just in case I run into a bad wire, from one end to the other, the ohms on your DC meter should read zero. If you get no reading at all, then the wire is broken somewhere. Today, I checked the wiring going to Pcm and did in fact find no reading on pin # 11 which is bank 2 , light blue wire going to rear Knock Sensor(code PO332), I could read front Knock Sensor ( PO327). I repaired pin 11 wiring. I recently send out for a pair of after market sensors which I strongly believe was a big mistake, upon installation, the SES light did disappear for a couple of miles, then both codes reappeared again( I had cleared them with my scanner before testing the run).In conclusion, I believe that the after market sensors might not be able to produce the same frequency as the factory sensors. I have now ordered GM sensors and should receive them soon. I will post my results.

**pajeff02** · 07-24-2016, 02:20 AM

There have been other posts on here regarding problems with aftermarket knock sensors. It seems that the problems always disappear when stock GM replacement sensors are utilized.