Soft codes 13 and 54 together needing help

[Jksconny]

When truck is warmed up cruising down the road cel light comes on and stay on for a little bit then shut off. It does this every time I take it out. The codes are 13-o2 sensor open circut and code 54-fuel pump circuit low voltage. What I’ve done to check 02 sensor with ign on engine off .3 volts at the signal wire. With code 54 I had engine idling and unplugged fuel pump relay and it still stayed running. Again these are soft codes and I sure appreciate any advice.

 

[fancyTBI]

Hey, you found the right spot to post! Awesome. Just be sure to give your vehicle details in your post! Seems like you’ve got OBD1 so a TBI truck?

 

[Jksconny]

Yeah, it’s a 91 5.7 tbi

 

[Schurkey]

How old is the O2 sensor? They get lazy with age. If you don't know when it was last replaced...it's time to replace it.

Consider converting to a 3-wire heated sensor instead of the 1-wire non-heated sensor.

An O2 sensor can't be "checked" unless the engine is running. Look for the voltage range--restricted range indicates a failing sensor; and look for the number of cross-counts. At idle, 6--8 is somewhat normal but more is better. As RPM comes up, 20+ crosscounts. More is always better. AND--no matter what the voltage, no matter what the crosscounts, an old O2 sensor is a damaged O2 sensor.

Download the service manual set for your vehicle from the links posted in the Sticky-thread section of the Engine forum. Trace your fuel pump circuit to determine where the corrosion/failing wire is, so that proper power can be restored to the circuit.