Dear Scotty,

Thank you for your videos, nice and clear, saved me lots of money!
I have 1999 Dodge Grand Caravan with 3.8 L engine, great car! Unfortunately it started to burn lots of fuel recently. Very poor gas mileage. I connected a scantool and it showed 2 codes:
-P0403 (Something about EGR solenoid circuit malfunctioning)
-P0171 (Fuel system lean, Bank 1)
First of all, the computer saying that the fuel mixture is lean, but the car actually burning lots of fuel, seems irrational, a false assumption by the computer.
I then observed the live data.
-The Short Term Fuel Trim B1S1 was around +/- 2% maximum
-The Short Term Fuel Trim B1S2 was 99% all the time, even at hot engine
-The both oxygen sensor (S1 and S2) readings were jumping up and down from 0V to 0.9V
-The Intake Manifold Absolute pressure Seemed OK, 38kPa at idle, and up to 120kPa at 2000RPM. It was following RPM closely
So, can I make two assumptions?
1) There are no vacuum leaks, and there is no too much air entering the engine, because the air pressure sensor is saying there is vacuum, and it is following the RPM.
2) The oxygen sensors are lying because they are saying that there is too lean mixture, where in fact it is way too rich. So the oxygen sensors (one or both) are at fault here.
Does EGR trouble code have anything to do with this?
I replaced PCV valve and hose because I accidentally broke them while inspecting the engine for vacuum leaks.
Is it correct that it is pain in the ass to change one of the oxygen sensors in this vehicle, because it is located behind the engine, similarly to the second row of spark plugs?

Wishing you all the best and with big thanks,

Andris Igaunis
Latvia, Europe

Comments
No. 1-1
Carquestions
Carquestions

If you have gas mileage issues - just because of its age it would be wise to change both oxygen sensors

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