1985 F150 300ci, 4 speed, 4X4. I found an EEC-IV reader, after KOEO test a 41 code appeared. I replaced the O2 sensor and received an all clear(10). Then moved on to verify that the TFI was advancing the timing properly and it is. Then we ran the KOER test and received a 41 code, bad O2 sensor. Where to I look now; bad replacement part, short in the wire or someplace else?

 

Code 11 is the Test Pass code.

Most likely you will need to add a ground strap to the closest bolt/nut to your O2 sensor on the exhaust pipe to the truck body.

You can measure the output of the sensor.

 

You are correct it should be and was in fact a Code 11. Can you walk me through the process for the ground strap, is not the manifold grounded through the engine?


Checking output of sensor? since there is only one wire do I remove the wire and check the sensor lead or do I leave check the wire coming out of the wiring bundle?

 

The single wire O2 sensor always had a ground issue, that's why they added a ground wire in later models.

Best spot to attach is the Y Pipe Bolt closest to the O2 sensor. I would add a ground strap there, and attach it to the closest spot on the metal body with a sheet metal screw.

You can check the continuity with your ohm meter from the base of the O2 sensor to the body of the truck to see if you have a ground reading. You may have a ground, then your issue could be further up the wire. But, an exhaust ground is not always consistent, that's why I always recommend adding a dedicated O2 sensor ground strap. (Here today, gone tomorrow)

There is a connector upstream from your O2 sensor connector that gets corroded as well and blocks the signal from reaching Pin 29 on your ECA. You may need to pull it apart and clean it.

 

Yeah, so you can check the output at the O2 sensor pigtail, or the connector upstream in the wire harness or at pin 29 on the backside of the connector attached to your computer.

Ultimately you may need to check the voltage at Pin 29 at your ECA to verify the presents of a signal.

The voltage is so small (0.0 to 0.1vdc), that any resistance along the way knocks it down. The O2 sensor generates the voltage after it heats up.

 

Thanks for your help. I do not understand the term Y pipe?.
Can I remove the upstream connector since instructions say cut and splice when installing new part?
Where is the ECA located? I thought about running a continuity check on the entire wire from ECA to O2 sensor.

 

Sorry, I had the 5.0L on my mind.....

Find a bolt closest to the O2 sensor on your exhaust pipe......

 

Ok, your new O2 sensor had no connector. The original had a connector, so your instructions are most likely referring to cutting off the connector or crimp connector a few inches away from the sensor. I recommend a solder connection vice crimp, on the O2 pigtail to wire harness. Also I like to use the sealant filled heat shrink.

Yeah good idea to check continuity on the entire path. Pin 29 to O2 wire. Measure the actual resistance, vice the beep.

Not sure on the 300, but most 85' ECAs are under the dash, just to the left of the steering column, or over on the passenger side.

 

The O2 first upstream connector only has one wire coming in and going out to the sensor. I like your suggestion of the solder joint and jell filled heat shrink.
Maybe someone following this thread knows where the ECA is located and is willing to share. Thanks again for you help. My schedule will not permit me to return to the shop until Thursday afternoon, however I will continue researching the exact location of the ECA, you have been very helpful.

 

Just looking at the 85' 4.9L wiring, they show a ground wire from ECA Pin 49 going to the ground side of the O2 sensor. (This may be an optional wire) You will want to check that Pin as well to see that you have continuity to ground.

On the 85' 5.0L drawing, Pin 49 shows to Engine Ground, your wire may physically go to an Engine Ground as well.

 

The ECA is a 6" x 7" silver metal box 1 3/4" in thickness with a 3 row 60 pin connector. 20 Pins per row.

 

That would suggest two wires, pin 49 and the one you mentioned earlier, however there is only one wire. If I can figure out how to transfer and upload a picture(computer challenged) I will send you a picture of what I have here.

 

You have the Feedback 1-V Carburetor ?

 

Not sure, some have called it an electronic carburetor. There are solenoids and several wires going to it. It is in fact a single barrel, I will try to send pictures of it also.

 

Well not necessarily, 85's were all single wire sensors I believe. But the ECA has some/a few dedicated grounds to the Body, Engine & Battery. So I would say you only have one wire to the O2 Sensor & the 4.9L drawing is showing a dedicated ground for the O2 and most likely connected to the Engine because that is the closest point to the exhaust pipe. (this wire may be optional)