O2 sensor not registering

[singularity]

hey everyone, recently I've had the p0171 and p0174 error codes coming up on my '98 Explorer Sport 4.0L EFI. I have an OBD scanner software (ProScan 5) which tells me that banks 1 and 2 are running lean. It also states that Bank 1 is stuck in open loop. I'm guessing that there is no feedback from the 02 sensor that's causing the open loop. I checked my MAF but it's clean. I haven't checked my intake gaskets though. There's also a jerk as I accelerate from low revs (don't know if it's the automatic transmission’s characteristics as it doesn't happen every time) and quite a bit of CO and unburnt fuel fumes from the exhaust. All O2 sensors show 0 volts and on trying to access the O2 diagnostics in ProScan, it tells me that the sensor is not present or not supported. I want to try changing the O2 sensors and the intake gaskets but being short on money I'd like to be sure of what's wrong. Thanks in advance for your help.

 

[Turdle]

The sensors are working, they are indicating excess air getting into the system.

There is an intake or vacuum leak.
Good luck.

 

[singularity]

thanks jt, I'll be checking the IAC and the MAF tomorrow. btw are the O2 sensors accessible in ProScan?