O2S Heater

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O2S Heater

louie
I have a 2000 silverado 4.8 O2S Heater won’t set already replaced two upstream sensors all monitors complete except Heater any ideas ?
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Re: O2S Heater

smog frogposter
Follow the enable criterias according to the drive cycle pattern, it may require you to leave the vehicle parked for a minimum of 8 hours for the coolant and sensor temperatures to go down sufficiently. It may also require you to perform several heatsoaks.
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Re: O2S Heater

No One
In reply to this post by louie
louie wrote
I have a 2000 silverado 4.8 O2S Heater won’t set already replaced two upstream sensors all monitors complete except Heater any ideas ?
Have you tried turning on the A/C defroster + headlights on high beams and letting it sit for a bit before taking it for a drive? 2-10 mins should be enough. Most of the time that does the trick. Try that and then drive it on free form test drive on the dyno(55mph) while monitoring the O2 sensors to see if they are responding.
   
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Re: O2S Heater

scanner
No One wrote
Have you tried turning on the A/C defroster + headlights on high beams and letting it sit for a bit before taking it for a drive? 2-10 mins should be enough. Most of the time that does the trick. Try that and then drive it on free form test drive on the dyno(55mph) while monitoring the O2 sensors to see if they are responding.
I find that after having the vehicle sit overnight, starting it in the morning and just putting it in drive will get the heater monitor to run.   Do the drive cycle the night before.  

The PCM is looking for time to activity.   You can setup a scanner and watch all 4 sensors KOEO after letting it cool down for at least 30 minutes.   You should watch all of the sensors drop to zero.   You should see the one causing the problem doing that.   You might look at the heater current with a scanner and see if one sticks out too.  You'll usually see it under the bi-directional control for the heaters.  
Why make it simple, when it will work equally as well complicated.
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Re: O2S Heater

RICHARDCRANIUM
In reply to this post by louie
Cold start with rear defroster if equipped and ac on will kick heater monitor in a heartbeat.
Shop owner 21 Years, 36+ year Smog Technician.
Inspector and repair Tech. I began in the BAR 84 platform.
Been current ever since. Momma said I hit my head a lot as a kid!
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Re: O2S Heater

Kevin
In reply to this post by louie
Check the heater control relay, and the sensors are going after the downstream. Not the Upstream.

On Wed, Feb 5, 2020, 2:32 PM louie [via Stop The Star Program] <[hidden email]> wrote:
I have a 2000 silverado 4.8 O2S Heater won’t set already replaced two upstream sensors all monitors complete except Heater any ideas ?


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