Hi, I’m having a problem on my 2003 Ford F-250 v10 with no o2 heater voltage on the passenger side, driver side o2 is functioning perfectly fine just no voltage on passenger side heater

 

Check fuse #23 in the underdash fuse box.

 

thanks for the suggestion, will do when I get home and will report back, I believe that it’s the ground from the pcm I believe that I’m missing, I have the 12v positive just not the ground, trying to help you understand my situation, is there a relay to the o2 heaters on the ground side?

 

fuse 23 is good, all fuses under steering wheel are good, not sure about relays

 

No relays to the O2 sensor heater circuit. You can see in the 2 diagrams below, the PCM provides the ground when it wants the heaters active.

 

interesting, could I have a bad pcm?

 

If the grounding wire is good all the way back to the PCM, yes you could. Make sure you also check the 12v at the sensor plug in with a testlight, not a digital voltmeter. You need to load the circuit down when testing, the digital meter does not present enough load if there were a bad connection in the 12v wiring.

 

how could I check if the ground is good to the pcm?

 

You would have to unplug the large PCM connector, find the correct wire, and then put your meter on ohms, backprobe the connector with one lead, and probe the ground at the O2 connector with the other lead. Of course you may need a scrap piece of wire to extend one of the meter leads to reach. You should get a reading very close to the same as you get by just touching the meter leads together, very close to zero ohms.

 

thanks, will have to do that when I get time, you wouldn’t happen to have a clue as to which wire it is going to the pcm would you?

 

The second diagram in the post #5 above shows it as pin 93 and 94.