1996 Ford Explorer Oxygen Sensors
Your Questions Answered about heated Heaters and other Issues
This weekly article strives to answer your questions about your automobiles. Today we discuss a 1996 Ford Explorer with heated oxygen sensor heaters.
This weekly Q&A session answers your questions about cars and trucks. This week explores a 1996 Ford Explorer with heated oxygen sensor heaters.
Question: 1996 Ford Explorer
Hello Mr. Ciulla: I hope you are doing well; I'm from Mexico so I apologize for my bad English. Below you can see that I started to solve an oxygen sensor problem. According with your suggestion I change one of the 3 sensors and now it shows a error P1113 and it seems like the sensor (the new one) is not working well.
The mechanic was checking the power supply of each sensor and there is not 12 volts to supply to the sensor heater. It seams like the computer (PCM) is not sending the signal to turn on the heater, could you help me to understand why the sensor is not receiving the power supply to the heater?
Is there any condition to turn the heater off? I already check the wire harness and it looks fine. Definitely the computer is not turning on the sensor heater.
Thanks in advance,
Saludos / Best regards
Jesús Antonio De La Rosa Monge
Answer:
This is how the Heated Oxygen Sensor (HO2S) circuit works: Power for the HO2S #1, #2 and #3 heaters are supplied by fuse 24 (15 amp) in the Power Distribution Box (PDB) via a light blue/orange wire. This fuse supplies power to all 3 HO2S's so if any of the HO2S's are not getting power then most likely the fuse is blown. There are 2 splices in that wire; the first splice (S142) carries power to HO2S #1 and the second splice (S179) powers #2 and #3. So the HO2S heaters are always hot, no pun intended. From the HO2S power is carried to the PCM by a red/white (#1), yellow/light blue (#2) and white/black (#3) wire. They go to terminal 387 (#1), 388 (#2) and 389 (#3) of the PCM connector. The PCM controls the ground to turn the HO2S heaters on and off.
So the first thing to do is check for power at the 3 PCM connector terminals for power. If there is power at those terminals, then the power supply and wiring is good and the PCM is not turning the heaters on. If that is the case, then the PCM is bad and needs to be replaced.
Now if there is power to only 1 or 2 terminals, then there is a wiring problem in 1 of those circuits. So then you will need to check for power at the affected HO2S. So the next place to go is the affected HO2S(s) and see if there is power at the respective light blue/orange wires. If there is power there, and there is power at the output wire, then the problem is in the wire between the HO2S and the PCM. If there is power in but not out, the HO2S is bad. And if there is no power coming in, and only one Ho2S is effected, then the problem is in the wire between the splice and the HO2S.
If you start at the PCM and work back to the fuse, which should be the first thing you should check, it should be fairly easy to isolate the problem.
That’s all for this week. Feel free to browse the archives for past topics.
