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Pete, Auto Service Technician
Category: Chevy
Satisfied Customers: 24143
Experience:  14 years GM dealer Technician.
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Chevrolet E350: working on 2012 chevy express van, 6.0 l.

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working on 2012 chevy express van, 6.0 l. getting a Po651 sensor referance voltage b circuit open. How do I find which sensor it is referring to?
Hi,my name is XXXXX XXXXX I will be happy to try to assist you with this.I may need more information in some cases to help with answering your question.

This code you have set here is for the 5 volt reference voltage on circuit 2 or B.The sensors on this circuit are fed 5 volts from the engine computer which are:

Accelerator pedal sensor1
Throttle position sensors 1 and 2
Crankshaft position sensor
Brake pedal position sensor

In some cases you can connect a scan tool and monitor the 5 volt signal for signal 2 or B and unplug these sensors one at a time to see if the 5 volt signal comes back when one is unplugged.If it does come back up to 5 volts when one is unplugged then the affected component unplugged is at fault most likely needing replaced.

I would double check the wiring repair that was done as well.If a wire wasn't repaired properly or is mixed up/crossed this may cause this here as well.

Thanks Pete
Pete and 6 other Chevy Specialists are ready to help you
Customer: replied 3 years ago.

that narrows it down considerably. is there an electrical diagram available for these sensors?

Copy and paste the below link to a new web tab or web page to view the diagram I have located on this.It is the 5V2 in the diagram.

Thanks Pete
Pete and 6 other Chevy Specialists are ready to help you

I am following up with you to see if you still needed help with your question you had asked.If my help didn't satisfy your question please let me know so we can continue.

Thanks Pete