PCM wont ground fuel pump relay

Charles Owner/Technician California Posted   Latest  
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2016 Ram 1500 Big Horn 3.0L (M EXF) 8-spd (845RE)
Pcm Wont Ground Fuel Pump Relay

This truck was a theft recovery, engine and transmission were stolen. Customer bought a totaled truck and had a hack shop swap it over. I installed and programmed a new PCM. After repairing multiple broken and cut wires and connectors I have no codes. If I ground the fuel pump control wire at the PCM the truck will start and drive fine. I assume if it was a security problem it would probably have a code and would shut off more than the fuel pump but I've been wrong before. If I command the fuel pump relay with the scan tool the PCM does ground the relay. I am suspecting a bad PCM.

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Robert Diagnostician
California
Robert Default
 

If you can command the relay on with the scan tool, then the driver and wires are good for the fuel pump control. If the computer is not commanding the pump on then I would say it is a programming issue. Is the truck configured correctly? Is there an option for a fuel pump control module in that year? Does the fuel pump get energized when the key is cycled? Does the PCM see that the key was…

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Robert Mobile Technician
Michigan
Robert Default
 

Hi Charles! Ok...a few questions. Was the old PCM communitive? If so, normally you would transfer the old PCM values to the cloud on FCA website. It is almost like Ford's inhale/exhale programming. If you did not do this it is not really an issue. You are going to have to do a few more steps. Being it is a used engine installed you will need to program the IQA's into the PCM. The numbers are on…

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Charles Owner/Technician
California
Charles Default
   

FIXED. Fuel pump enable. Why would you need to enable the fuel pump. Isn't it be assumed that you would want the fuel pump to run when you install a new PCM. I had done everything else. Thanks

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Rick Technician
Illinois
Rick Default
 

Thanks for sharing that. I have done a few of those PCMs and never ran across that before. I have always been able to use Witech to transfer the data. I never realized the fuel pump enable was an option. Good to know in case I run into that.

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Jose Technician
California
Jose Default
 

Bob thanks for the good info!

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Caleb Diagnostician
Indiana
Caleb Default
 

Wow very good tidbit of info!!

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