I am going on a road trip and recently got the engine replaced. On our way out, a CEL and I checked the OBD2 and read P113. Also through the OBD2 I read the live sensor data while the car was running (not idle) and it shows low voltage, lower than the 0.1v I’ve heard is the minimum range (picture attached). It’s quite cold on our journey and I don’t know if that might have something to do with it. The engine seems to be running fine with no hiccups(starts, idles and runs just fine). I’m hoping it’s just the sensor but I’m not sure and would like some advice. Like I said it’s a new engine so I doubt it’s any vacuum leaks or anything on the engine itself. Thanks

Sensor Value B1S1

 

Welcome to the forum

What year and what model engine?

P1131 Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 1

O2 sensors are the only sensors that wear out, 100k miles or 12 years

So they need to be replaced after either 100k miles or 12 years which ever comes first
And they go "lean" as they get older

If they are in need of replacing then just do it, you will get best MPG with working O2s

If O2 sensors are newer then you may have a small vacuum leak or fuel pressure is lower than it should be
But need the Year and Engine model to go further

 

2000 3.0L

 

21 years old so should be on 3rd set of O2 as this time, should have 3
One on each side of the engine near
One on the single exhaust pipe after Cat converters, that's "sensor 2", S2, should be steady at 0.7v to 0.8v, yours is a bit low

Yes, both "sensor 1s" S1s, should average 0.4volt
B1S1 and B2S1 are the two "upstream" O2s
B1S2 is the "downstream" O2 after Cats

If BOTH upstream O2s are showing "lean" then its most likely a vacuum leak or fuel pressure issue
If just one is "lean" then can be lower intake air leak on that side but most likely is just an old O2

 

All right so here’s some sensor data from it running today, it seems like the sensor is back in the normal range so I’ll be looking for a leak.