So here it is, If anybody has any ideas on all ears. I replaced my motor about 2 months ago. All the sudden I had the check engine light come one right when I wanted to register my car! So I checked the code and PO155 came up. So I replaced the front driver side upsteam Oxygen sensor. So reset the light and drove for about 30 miles. Light came back on. PO155 again! So I replaced the passenger side upsteam. Reset light and drove. Another 30 miles light comes on again!!!! So I run a check on all the sensors. They all have power and working correctly. but I'm still getting PO155!!!! Does anybody have any ideas??? Oh yeah its a 1998 Ford Expedition 5.4L

Thanks!!!

 

http://www.obd-codes.com/p0155

Causes

A code P0155 may mean that one or more of the following has happened:
O2 Heater element resistance is high
Internal short or open in the heater element
O2 heater circuit wiring high resistance
open or short to ground in the wiring harness

Possible Solutions

Repair short or open or high resistance in wiring harness or harness connectors
Replace oxygen sensor (cannot repair open or short that occurs internally to sensor)

Bank 2 Sensor 1 is driver's side upstream.

 

Yep, 150 series, - either the wires/connector or sensor itself.

Grey is ground. (direct PCM ground)
Black is sig.
Whites are heaters.