My fixd scanner only says low voltage. How can I increase the volts at OBD connection my check engine light is on trying to get code.

1999 GMC Sierra 2500 with a 5.3 litre Vortec engine

Scanner works on my other vehicle.

  • I put a remanufactured engine in my truck I get error codes coming up I go to AutoZone to keep reading them different zones all the time so I bought my own fixed scanner it will not work it reads low voltage what do I do
    – Jim
    Jul 30, 2020 at 18:41
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    Welcome to Motor Vehicle Maintenance & Repair! Have you checked the voltage at the battery? Does the vehicle start? What's the year/make/model/engine of the vehicle in question? Jul 30, 2020 at 18:42
  • 1999 GMC Sierra 2500 with a 5.3 Vortec liter engine and yes it starts at Rodney but every so often it check engine light comes on I have 34 miles on the new engine can't use my fixd scanner keeps saying low voltage LED OBD how do I increase voltage when it's already between 12 and 14
    – Jim
    Jul 30, 2020 at 18:45
  • If the battery voltage is correct (like you state), then the only thing left to do is get a different scanner. The OBDII port has a pin for battery voltage which it supplies to power the reader. If the reader isn't liking it, it's the reader's problem I'd bet. You might see if you can find another you could use or take the vehicle to a major parts store (like Autozone) to see if the codes can be read. Jul 30, 2020 at 18:50
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    Those codes really don't mean anything to me. That isn't the format for OBDII, as they start with a letter, followed by four digits. If these are specific to the reader, then you'd have to look in the references provided by the manufacturer to get a better idea about them. Jul 30, 2020 at 19:10

2 Answers 2


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Make sure you have battery voltage on pin 16, and ground at 4. If you have voltage, probably have scanner problems.


Check for corrosion or discolored pins on the tester and receptacle. Your tester could have bad connection internally causing it to “see” a low voltage from your vehicle. If you have a multimeter check for the correct voltage at the test receptacle. If that’s not where it should be, I would trace the wiring looking for a resistance (ie, corrosion or loose connection) that shouldn’t be there. You may have pinched a wire when you installed the new engine. I hope this helps, Good luck!

I have 35 years experience doing electrical and avionics work on military jet aircraft to base my thoughts on.

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