I just checked this website last night because I was having problems eliminating 171 and 174 codes. You guys are right on the money with the PCV hose. Mine was broken in half. I wish that I had found this website $450 sooner.

Now I have 411 and 420 codes.

My truck is a 1996 F150 4.9.

I think that this may be bad CATS, but I am not sure.

Any help would be appreciated.

 

P0411 Diagnosis

While there might be a problem with a cat, I'd focus on the Secondary Air Injection system first. If there is a problem there, it will skew the exhaust and mixture readings so that the catalyst monitor test may not be valid.

Do you have the electric or mechanical air pump?

Here are the first diagnostic steps for each system:

Mechanical:

Electrical:

 

I believe that I have the mechanical air pump. It runs off the serpentine belt.

I don't believe that this is a vacuum leak. I just inspected all vacum lines on Saturday. I was trying to alleviate the 171 and 174 codes.

I will check the lines coming from the air pump and the AIRB/AIRD.

How do you know if the AIRB/AIRD is functioning properly?

I have vacum on one side, but nothing on the other. I assume this is because it gets diverted at a certain speed. How can I test this?

I am also unsure as to what <<HM81>> and <<HM41>> are. Could you please explain.

On a final note, I should say that in the course of trying to fix the lean codes, I changed the downstream O2 sensor. Would this have anything to do with these new codes?

 

I performed the test on the AIRB/AIRD Valve and the valve failed when I tried to put vacum on both the bypass and diverter ports.

I am going to replace all of the hard plastic vacum lines with new rubber hose.
I did not find any leaks or mis-routing, but while I have the entire vacum harness on top of the manifold, I feel I should run new lines.

I took a digital photo of the VECI decal and printed it out so that I would have a diagram that was readable during these checks.

I will try to get the new valve tomorrow and put it on.

Should I reset the codes?

Thanks again for the troublshooting list.

 

check the filter on top of the egr vacuum solenoid too,it pops right off,it sure made a difference in mine when i cleaned it.

i still have the lean codes too,im gonna check out the pcv hose too

 

I disassembled the AIRB/AIRD Valve and cleaned the diaphrams. I reassembled and tested for vacum and performed the tests from the Haynes Manual. All seems to be working. I will drive it today and see if the P0411 code returns. I also believe that this may clear up the P0420 code as well.

We shall see.

 

These are the step references in the diagnostic procedure.

Looks like you're on top of it for now. If you do need the continuation of the factory diagnostic procedure posted, let me know and I'll post them.

It may take two or more complete drive cycles before the CEL comes back on if any fault still exists. Testing conditions are rather specific and sometimes are not met on any given drive cycle if prerequisite conditions are not met. A "pending" code will be set after one test failure. It usually takes two consecutive failures to turn on the MIL.

Steve

 

Thanks Steve.

That was my next question on how long it takes for the monitors to reset.

I actually took the truck to emissions and the computer aborted the test because the Catalytic monitors had not reset.

I put about 160 miles on today. Starting and stopping at times in between.
Usually for about 15 minutes in between restarts.

I will keep everyone posted.

Thanks again for the help.

 

I have about 440 mile on several drive cycles and I followed the ones from Ford in regards to OBD II and I am still showing a P1000 code and I can not be tested by emissions.

I purchased this truck 7/04 and the guy I bought it from failed emissions in 1/04 for a bad catalytic convertor. I believe it was a P420.

All my monitors have reset except the catalyst readiness monitor. This is why the emissions test in Connecticut keeps aborting.

Any further suggestions?

I changed the T-Stat and the temp sending unit today. I had to splice the wire for the temp gauge because it was broken. I now have an operational temp gauge that is all over the place. It goes very far to the right when I drive the truck hard, but moves back to the middle if I cruise at about 65 for a few minutes.

I changed the T-Stat because the emmisions test center said that the truck may be running cool and not allowing the H02S to heat up enough.

I can't believe that this drive cycle needs to go on too much longer. I would rather see the Check Engine Light come on. At least then I would have a place to start.

Is there a way to test the HO2S?

 

Getting a Ford to run its on-board readiness monitors can be an exercise in frustration. My Contour took three weeks to run the EVAP routine.....

There is no direct linkage between the thermostat and the O2 sensors as suggested by the testing center. There is also no indication that the O2 sensors are in need of testing.

However, if your temperature is oscillating widely, the ECT will pick that up and may prevent the test from running as a sable reading formn the ECT is one of the test prerequisites.

As for the potential P0420 code, a MIL eliminator or a new catalytic converter will likely be needed. If it were my truck, I'd splice together the eliminator circuit into the downstream sensor harness without delay since cats seldom, if ever, repair themselves while driving. The parts for the MIL elimintators cost about 2 bucks at Radio Shack and can be assembled by anyone with soldering skill.

Steve

 

The Saga continues.

I found out yesterday that the T-STAT housing had a crack in it.
I replaced the housing and filled the radiator with coolant, 50/50 mix.
This time allowing the engine to warm and the T-STAT to open and circulate the coolant. The temp gauge is working fine now. I topped off the radiator and drove the truck.

The Check Engine Light came on again. I went to my favorite AutoZone and the codes came back P0411 and P0420.

I found that one of my new vacum lines had melted on the EGR pipe that goes to the exhaust. I bought a length of heater hose and routed all vacum lines through the hose.

I cleared the codes and followed the prescribed Drive Cycles by Ford to reset all PCM monitors.

Well, what do you know, the Check Engine Light came on after about an hour of driving. I went back to AutoZone and this time I recieved only one code.

CODE P0420.

From what everyone is posting, there is no fix for this code other than replacing the CATS.

My problem is, this CAT Setup is proving difficult to locate. AutoZone does not stock it nor is it available.

CarQuest gave me a Part# 645898 for a price of $330.73

Ford wants $1100.00 for this baby.

Is this truley a CAT replacement?
Will the MIL Eliminators fool the Connecticut Emissions Testing?

Thanks again for the help.

 

Yes. They do it every day. The PCM thinks the cat is working so it never sets a code. Since the states are no longer doing tailpipe testing, they'll never know it.

Steve

 

Thanks again. I am going to replace the exhaust system. My buddy is getting the parts for cost. I am definitely installing the MIL Eliminators, because I don't want to have to go through this again.

I will keep the updates coming.