1996 4.9 L engine, the o2 sensor on the front exhaust manifold keeps burning the heater. have changed it 2 times. First time from junkyard, second time new from AZ. I have checked fuse, wiring, relays. I can come up with nothing. Does anyone have any ideas where to troubleshoot ? Some manual says PCM is bad, just want to be sure before I spend any more money. Truck has 208800 miles on it. Thanks in advance for any reply.
RR

 

test the voltage....

 

Elec component from the junk yards is never a good idea. I don't know what heater it could be burning up.

 

O2 sensors are a Heated Wire type...

you have the Signal wires which are usually Black and White and all brands usually the Heater wires are Gray....

 

What brand did you get from AZ? I agree that the one from the JY was probably on it's last leg. AZ has some pretty dicey parts, I've had good luck with the parts I've gotten there but have heard plenty of stories about junk parts. I used the BOSCH 15717 from rockauto (like $20+ each) and can't complain, though I just put them in this week.

 

I replaced both banks with the bosch, I also replaced the ECU just to clear up the airbag code. The little fuse was out causing a code 51 on the airbag light. I think that this cleared up the o2 sensor also. I will be checking out rockauto on some parts for a upcoming project. Thanks for the reply,