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Pete, Auto Service Technician
Category: Chevy
Satisfied Customers: 29109
Experience:  14 years GM dealer Technician.
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Code po651 car will run 10 or20 milrs then check engine

Customer Question

code po651 car will run 10 or20 milrs
then check engine light comes on and loss of eng power shows up on dash
Submitted: 4 months ago.
Category: Chevy
Expert:  Pete replied 4 months ago.

Hi my name is ***** ***** I will be happy to assist with this today.In some cases I may need more info to assist better.I apologize for any delay.

This code indicates a 5 volt reference circuit ( circuit 2) is at fault here.

The 5-volt reference 2 bus provides 5 volts to the following sensors:

* The APP sensor 1
* The throttle position (TP) sensor 1 and 2
* The crankshaft position (CKP) sensor

If any of these sensors are shorting out internally this causes this fault here.In most cases it is the crank sensor or throttle position sensor.

Important: Additional DTCs will set when disconnecting the components.

1. Ignition OFF, disconnect the harness connector of all appropriate sensors for the applicable DTC.

Important: A short to voltage on the signal circuit of certain components may cause this DTC to set.

2. Ignition ON, measure for 4.8-5.2 volts between one of the 5-volt reference circuits and ground.

^ If the voltage is less than the specified value, test for a short to ground on all the 5-volt reference circuits. If all circuits test normal, replace the control module.
^ If the voltage is greater than the specified value, test for a short to voltage on all the 5-volt reference circuits, or the signal circuit, for each component associated with the appropriate 5-volt reference circuit. If all circuits test normal, replace the control module.

3. Connect each component associated with the 5-volt reference circuit, one at a time, while monitoring the voltage. The voltage should not change more than 1 volt.

^ If the voltage display changes more than the specified value when a component is connected, replace the component.

The testing above has to be done when it is acting up.One other way to check it is when acting up unplug each of these sensors 1 by 1 and clear the code to see if when one is unplugged the code clears out and stays cleared out.If you find one sensor when unplugged does allow the code to clear and stay out then that sensor needs replaced.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service,your 5 star rating is appreciated.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete