I have a 1998 Ford Explorer 4.0 V6 with 200K miles. I plugged an OBII scanner with live data readings and my o2 sensors never relayed any information (voltage), they all ead -100% and the voltage never changed. Could all four be bad? I left the truck running for 15 minutes with the scanner attached and nothing changed.

BANK 1 SENSOR 1 = -100%
BANK 1 SENSOR 2 = -100%
BANK 2 SENOR 1 = -100%
BANK 2 SENOR 2 = - 100%

 

I have a 97 that displays the same behavior using standard OBDII live data scanners.

When I connect using my Harrison/laptop with extended Ford PIDS, the O2 sensors are readable and viable..... Philip

 

It means your scan tool does not support the early Ford Truck PIDs. Many of the Ford trucks (an Explorer counts as a truck) are not fully compliant with OBD-II standards, but rather used a Ford specific PID system. Later on the trucks became fully complaint, and use the same PIDs as the cars.

In order to read those sensor values or your fuel trims, you will need access to a better scanner.

 

The post from KhanTyranitar helps a great deal. My cheap scanner will read the O2 PIDs on my Windstar but not my Aerostar. I was beginning to believe that I have a bad PCM, but I built an O2 sensor dummy out of a voltage divider and potentiometer and the PCM responds. It just never reports either trim or O2 sensors.

So now that I know that I need a new scanner, which one will let me read the older Ford Truck PIDs? I cannot afford the Rotunda version. What else works?

Thank you very much.