My 98 threw a check engine light the other day and after retrieving the codes I got the usual "lean condition bank 2". Although after hooking up my scan tool, I found that three o2 sensors are not responding. All zeros across the board. I just changed the bank 2 sensor not even 500 miles ago. Im guessing with 3 going out at the same time I have a wiring issue.

Does anyone have a wiring diagram for the o2 sensors on a 98 Expy with the 5.4?

 

See the attached PDF, and take note there are 2 pages. Sorry, can't do anything about the resolution.

FYI, the O2 sensors labels translate as:
#12 = Bank 1, Sensor 2
#22 = Bank 2, Sensor 2
#11 = Bank 1, Sensor 1
#21 = Bank 2, Sensor 1

 

typo, s/b:
#21 = Bank 2, Sensor 1

FYI, Sensor 1s are for fuel control.
Sensor 2s are for CAT monitoring.

 

Thanks for the info. I lost os21,os22 and os12 all at the same time. I dont get it. It doesnt really look like they share a common fuse or ground. Anyone got any ideas?

 

Were you looking at the heater circuits? Or the signal circuits?
The signal circuits won't generate any voltage until they come up to operating temps. And the heater circuits shut down after a fixed amount of time after startup.

 

After the cel came on I hooked up my scanner and viewed the real time data and the three dead sensors were at 0.000 volts while the truck was running and warm. The bank one sensor was switching no problem.
My truck has raised fuel mixtures 12.5% and Im guessing thats because of what it perceives to be a lean condition. On a road trip last week I only got 270 miles to a full tank on the expressway.
I need to fix this

 

Fixed it...

 

I would change the bank 2 sensor and see what happens. The two rear sensors might be disabled since there's no communication with the front bank 2 sensor.

One time the wife drove my Mustang through a deep puddle (up to the floor boards) and that caused all 4 O2 sensors to go bad. So just be aware that it is possible something happened to all 4 at once for some reason.

 

When my bank 2 sensor went out 4 months ago the rear two were still working. I put a new sensor in bank 2. It doesnt even have 500 miles on it. Is there a fuse for the sensor power?

 

I know starting in 1999 you have fuse #23 (15-amp) for the front O2 sensors and fuse #24 (15-amp) for the rear O2 sensors. But for 97 and 98 I think it was different. You can check those 2 fuses just in case.