I looking for info on how many Oxygen sensors there are on a 1997 F150 4X4 with the side outlet exhaust pipe. Are there 2 upstream and 2 downstream or only 1 each?
I don't have the truck here right now or I'd go look myself.
Thanks

 

You Have Two Hegos And One Cat Monitor....

 

You have four O2 sensors. One on each side before the cats and one on each side after the cats. When I replace mine I get the ones for the rear with the long wire harness. I coil the harness and secure it with a Zip Tie. I only replace two at a time. The new ones go to the front, the front ones go to the rear and the rear ones go to the dump.

JMC

 

As JMC said, four.

However, there's no real operational reason to replace all of them.

Personally, I only replace them one at a time as they're needed.

You might want to start over and describe what your circumstances are. There are many faults that might point to the sensors for the inexperienced, but are not due to the sensors themselves.

Steve

 

On a 2000 f-150 do i get long wire or shorter wire for upstream sensors?

 

If in doubt, get long - you can always coil up and tie off the excess but you can't stretch them.

 

OK, a little background about why I was asking about the O2 sensors on my truck.

I have thge DREADED P0401 Disease!!!!
The statistics:
1997 F-150 XLT 4X4 Automatic Transmission.
4.6 "W" Engine with 203,000 miles, and I believe the original O2 sensors.

Last November, just in time to need my emissions testing to get my license plate renewed, I got my first ever CEL. Took it to Autozone, read as P0401. Then took the following steps to correct it.
1. Cleaned the EGR Ports in the throttle body, and boy, they needed it.
2. Replaced the EGR valve (stupid, I know I pulled a vacuum on it and the engine stumbled as it should have)
3. Replaced the DPFE Sensor with an aftermarket one, (I started reading the forums about then).
4. Pulled the stainless steel dpfe tube and checked it for cracks or damage, none found.
5. Replaced the EGR Solenoid.
6. Pulled the vaacuum reservoir and tested it. It's airtight and good.
Still no joy, but I found the tube to the PCV valve had a LARGE hole in it, replaced it and all was well. I had since purchased my own code reader by this time. I passed the emissions test, and was happy, for a while.
Two months ago, like a bad dream, it came back.
I went to Ford and got a FOMOCO DPFE ($120,Ouch) and put her in.
Nope, still there.
Put in the original solenoid to see.
Nope, still there.
Replaced the TPS.
Nope, still there.
Cleaned the MAF
Nope, still there.
This is getting expensive, but look at all the spares I'm collecting.
So, this weekend, I put two vacuum gages on the truck and took it on a 70 mmile drive to see my Dad for Father's day. An interesting thing showed up.
One vacuum gage was on the line to the EGR valve, the other on the supply line to the Solenoid.
The supply to the solenoid varies with engine speed somewhat and with throttle position as you'd expect. But.... At first the vacuum to the EGR valve varied with throttle, as long as you're not at the idle position on the TPS, just as you'd expect. But after a few miles the vacuum just stopped, and if you hit read on the code reader after a few more miles, sure enough, you see a pending P0401 code. Stop and idle for a couple of minutes, and the vacuum to the EGR starts behaving again for a few miles and quits again. Keep driving and you get a CEL on the same code.
Why do I think it might be an O2 sensor?

1. Look at all I've eliminated above.
2. The O2 sensors have 200K + miles on them.
3. This morning, I still had the vacuum gage setup still on the truck and tested it on the way to work with a "cold" engine. All the previous testing was on a "hot" engine.
I had "good" vacuum input to the EGR for about 13 miles of continuous highway driving before the vacuum shut down. Seems like it takes a while to get everything really hot to fail. I have read here and in the Haynes/Chilton guides that the MAF, TPS and O2 sensors play a part in generating a signal to the EGR solenoid. Also, a while back a Ford tech I see at the mall food court occasionally said O2 sensors could cause this and not throw a code. He has advised me on a few other items ( I changed my own heater core) and he's has seemed to be correct in the past.
I think that something is sending a signal to the solenoid to shut down the vacuum to the EGR valve. I just don't know why. I plan to wire a voltmeter to the solenoid next to see if the voltage to it goes away, shutting down the vacuum signal.
I'd appreciate any ideas or suggestions on this. I swear I hate the thought of paying $85/hour to the dealer. I've got till the end of November, but I'm determined to conquer this.
Thanks for reading. If I fix it I promise to update this thread.

 

If you have 200k on O2 sensors, I think I'd replace them on general principle.

 

Info on PO401 -



You go here for the low down -

http://www.fordscorpio.co.uk/egrmonitor.htm

 

I wouldn't. Can't think of anything they'd have to do with his EGR problem. If they aren't bad, there is no justification for the waste of money in replacing them.

No. However, their diagnostics (monitors) must have successfully run before the EGR flow monitor will begin. Also, they must be indicating to the PCM proper operational conditions.

Consider this: EGR flow is commanded by the PCM only during steady-state driving conditions. It is never ordered at idle or during acceleration or deceleration.

The EGR system is shut down by the PCM when the monitor runs and fails. That's why you're seeing the vacuum to the EGR valve disappear.

Have you ever looked at your freeze-frame data or run the KOER self-tests? Both provide critical data about the failure and the diagnostic for it.

Also, disconnect the hoses to the DPFE sensor and see if there's any water in there.

Steve

 

I don't have the procedures or results documentation for the KOER tests. I have done them on an '88 Ranger I once had (to diagnose a bad TPD), but done have any thing on the '97 F-150. If you know where I can get them, I'd appreciate any info you have.
The DPFE hoses have been off numerous times now, including a time to remove the stainless steel EGR pipe with the sense ports for the DPFE in order to look for cracks or obstructions.

Thanks for the help.

 

Freeze-frame and KOER data must be acquired using an appropriate scan tool. Low-end models won't have this capability. Don't know what you have or what its capabilites might be, A scan tool with Mode 6 data capability would also be very helpful.

Do you have the PCED so you can consult the FACTORY diagnostic procedure? If not, google "Ford Service CDs"

Steve

 

I have a Ford CD with diagnostic prodedures on it.
My scan tool is just a reader/eraser (<$100), but it has proved to pay for itself so far.
Thanks again

 

i had the same problem. after new egr valve, cleaned TB, and new dpfe from autozone, its fixed. the dpfe was the problem, and 3 months later the autozone version of the part is still kickin.

 

Well, at least you do have the PCED. See section HE90 and following.

Back probe the output pin of the DPFE sensor, use a hand vacuum pump with a gauge to apply a vacuum directly to the EGR valve at idle and watch the output of the DPFE sensor.

You should see a direct correlation between the vacuum applied to the valve to the output of the sensor. You will likely have to manually operate the throttle to keep the RPMs up, over 1K is usually okay.

The output of the sensor should be almost linear from about 0.5 vdc up to 4.5 vdc with an applied vacuum from around 1.5 up to 10 in-HG.

If you do see the rise but don't get enough, your passages are probably still (or again) restricted.

Remember, the DPFE sensor is supposed to measure the difference between the relative pressures or vacuums present at the inlets. You can install one of your vacuum gauges into the downstream inlet line (the upstream line stays relatively constant) and watch the inputs to the sensor while watching the output voltage. Again, the relationship should be relatively linear.

Steve