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86-95 Trucks & 4Runners 2nd/3rd gen pickups, and 1st/2nd gen 4Runners with IFS

code 12- O2 sensor

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Old Sep 10, 2008 | 10:23 AM
  #1  
Hayes's Avatar
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From: Aurora, CO
code 12- O2 sensor

new engine, rebuilt bottom end .010 over. ENGNBLDR.com STREETRV head, new injectors, cap rotor blah blah blah... Replaced the o2 sensor and the exhaust manifold (was cracked), still getting a code 12. I have cleared multiple times. What is wrong? Why won't this code go away?... It did take a little longer to come on this time though. I'm going crazy trying to get this damn thing running. Anyone had problems with the Street RV head causing problems?

I am double posting in the 84-85 and 86-95 forums since this engine was used in all the years...
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Old Sep 10, 2008 | 11:39 AM
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From: Temecula Valley, CA
well... what year again? code 12 means different things in different years
and 12 has nothing to do with O2

Last edited by abecedarian; Sep 10, 2008 at 11:42 AM.
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Old Sep 10, 2008 | 02:58 PM
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From: NW Ark on wooded ten acres...Ozarks at large!
And are you sure it's a code 12? Although, I can't imagine mistaking that one.
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Old Sep 10, 2008 | 03:03 PM
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yeah, but i realized that I mixed up code 5 and 12...I had both originally. I am having knock sensor issues.
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Old Sep 10, 2008 | 03:07 PM
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From: Temecula Valley, CA
so...
you're sure it's good?
you're sure it's plugged in?
you're sure the knock sensor is installed in the proper location?
you're sure the wire from the knock sensor to the ECU is in good condition?
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Old Sep 10, 2008 | 03:37 PM
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From: Aurora, CO
Originally Posted by abecedarian
so...
you're sure it's good?
you're sure it's plugged in?
you're sure the knock sensor is installed in the proper location?
you're sure the wire from the knock sensor to the ECU is in good condition?


ha ha, no. After I talked with TC, I realized I was trouble shooting the wrong issue...back at it tomorrow.
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Old Sep 10, 2008 | 03:42 PM
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From: Temecula Valley, CA
lol...

now I'm not 100% sure about this, but I've seen it on the web, that the knock sensor wire is a shielded type wire, meaning it has a center conductor and a braided, or other type of conductor, like TV coax cable, surrounding the center conductor and that the factory for whatever reason didn't ground the wire at either end, so when you start looking at the wiring, you may want to check that. The purpose of the shield is to keep any electrical noise from the engine area- fuel injectors signals, ignition noise, etc, from affecting the signal to the ECU, which could cause the ECU to think there was pinging/detonation when there wasn't.

At worse, even if it's not shielded, you may want to replace the wire with a shielded wire and ground the shielding next to the ECU since the signals sent by the knock sensor are very weak and extremly succeptible to noise on the wire.

Last edited by abecedarian; Sep 10, 2008 at 03:44 PM.
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Old Sep 10, 2008 | 03:53 PM
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From: Aurora, CO
my first step is going to be making sure the torque is right and then tracing the wiring and all back. Thanks for the advice.
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