Hey guys! I know there have been many threads about the neutral safety switch throwing codes. I have read through most if not all of them and I am having a different issue than others. I have a 2000 F-150 Lariat 5.4L/V8 and have no issue with starting. It started hunting for idle and I naturallly assumed it was a dirty mass airflow sensor. I cleaned it with MAS cleaner and intented on driving it for a bit to hopefully reset the computer. After a day or so, the check engine light came on. I had the code read and it was P0705. The neutral safety switch has never been replaced, so I figured it was probably bad. I replaced the switch and left the negative terminal disconnected and the check engine light went off. Not long after starting the truck, the check engine light came back on. I again had the code read thinking it would be different, but it's still throwing P0705. I took the switch back off and ensured the marked neutral line on the switch was properly aligned. I also checked all the harness wires at the switch. None of them look frayed and the pins seem to be seated. I cleaned the harness well with contact cleaner. I'm still getting the same check engine code and it's still hunting after driving for over a week. I can not find the spec sheet on the switch to check the resistance to ensure the marked neutral line is correct. The switch has 11 pins, and I can not find any schematic for that layout. Does anyone have the pin schematic with the resistance ranges? Also, any other ideas on next steps would be appreciated!

 

Since the range sensor shouldn't have anything at all to do with engine idle behavior, but the two problems are coincidental, I would first check to see if they are on the same power supply and grounds, or share a harness. If you're positive that both problems occurred at the same time.

If they didn't occur at the same time I would address them separately. And, the MAF sensor is not the thing to focus on for a hunting idle. Don't replace it. The IAC valve controls idle RPM. But there are other things that could cause the computer to try to affect idle RPM.

It might help to give more detail on the idle behavior. Does it happen when cold or only after warm up? Does it happen in Drive or only in Park or Neutral? How far does it move, 50 RPM or 100?

Good luck.

 

I'd be deep into a 2000 PCED doing the pinpoint test steps for code P0705

 

The range sensor could affect the idle, if the PCM is confused on which gear it's in/receiving improper signal. It's hunting in park. In neutral, it's hard to tell if that smooths it out or not.

 

Unfortunately, I don't have a scan tool to run the full test. This weekend, I plan on checking the neutral reference line on the switch itself by testing the resistance, just to ensure it's actually aligned properly. Then I'm going to test the wiring end to end to see if I have have a short or break somewhere.

 

Years ago, my son replaced the pigtail on his F150 with 6R80 trans. I joined a web site that I could download the wiring diagram for a fee. I don't remember the name of the site but was able to trace all the wiring.

 

What do you mean by "hunting"? Randomly rising and falling or periodically falling and rising? And you haven't said if the engine is warm or cold. Might be a clue there. Also, is your AC compressor engaged? Set your heater to Off and see if anything changes. Compressor load will cause RPM ro change.

The IACV is the fast-acting device that the PCM uses to control engine speed when the throttle is closed. If it reacts slowly you'll get an unsteady idle.

 

It's random when cold. Hard to say if it changes when warm really. AC was on, I can try it off and see if it makes a difference.

 

The pinpoint tests will tell you exactly what to do
A good visual inspection looking for bad connections and pushed out pins in connectors is the first step
Ohming out wires back and forth is always a good idea
The pinpoint tests will have you do all of that depending on some parameters based on your particular code
Buy one of these 17-dollar scan tools and go to town checking a few things
Get the PCED info from the library off AllData, free at most public libraries

Ebay, currently 17.00

 

I was able to get all the testing procedures from CoPilot AI. It even gave me alternatives without the scan tool. I'll probably end up getting one anyway though. Save the hassle of running to Autozone all the time.

 

Right on
Good luck, let us know how it goes
Maybe Copilot can help me out and save me trips to the local library where I go twice a week
Thanks for that

 

I looked for the pin schematic for two days, no joy. I just wanted to verify the reference line for neutral on the switch was actually accurate. Typed it into CoPilot and it popped right up with the full pin out and resistance table. Pretty scary actually. Apparently we didn't learn anything at all from The Terminator 🤣

 

Just because it's there and seems amazing doesn't mean it's correct. Be careful. I've seen blatantly wrong info presented by the various A"I" tools. Use the references that AI pulls up with the summary.