Greetings,

First the pertinent info:
'96 Ext. 4.0L V6 XLT Dual Air 117,000 miles.

Didn't pass emissions yesterday due to the following:
P1443
P0171

MIL Status: MIL Command On: Fail

Readiness Monitors That Are Not Ready:
Catalyst

I'm pretty handy under the hood and usually do my own vehicle maintenance/repair work. But I'm at a loss trying to diagnose and interpret all of this together. Any help making sense of it will be greatly appreciated. In fact, I'll even add you to my Christmas Card list

Thanks,
Steve

 

P0171 is the code for lean on bank 1 It is usually caused by a vacuum leak or a dirty Mass Airflow Sensor. Other causes have been reported to be everything from a bad 02 sensor to bad spark plugs.

p1443 is the code for the the evaporative fuel canister. This code pops up when there is a disturbance in the flow in the vacuum line from the canister to the engine.

I had the p0171 that kept popping up from time to time and I chased it until I was ready to scream. I changed everything from the 02 sensor to the engine temp sensor and it would go away but it kept popping up. I even bought a new fuel pressure regulator and had it all ready to install.

Then the van started throwing the p1443 code too. I changed the vacuum solinoid and the valve ( both located under the air filter box on the side of the canister) This fixed the P1443 and guess what? The P0171 went away as well and has not reappeared!

The hoses on the evaporative parts were in bad shape so I coated them with silicone sealant just to make sure there were no leaks. I know, I should have replaced the hoses too but I din't have any at the time.

As a side note, my van was throwing these codes when I took it in for smog but I drove the van around until it got well warmed up, then I cleared the codes and drove into the smog shop right on time for my appointment. The van passed with flying colors and then the codes popped back up on the way home. I replaced the parts a few days later.

I suspect the evaporative parts were leaking all the time and causing the p0171 code all along and when it got really bad it finally tripped the p1443 code.

The funny thing about these OBDII codes is that the codes really just report what sensor got a bad reading. The real cause can be somethig else but it will related to the operation of the sensor that trips the code.

The evaporative code p1443, for example could be caused by bad parts or the vacuum hose that runs all the way back to the fuel tank could be bad as well. Or the hose from the cansiter to the enginge could be leaking. There is even a vacuum valve on the top of the fuel tank that could also cause this code I belive.

After you install any new parts, clear the computer (disconnect the battery for a few minutes if you don't have a reader that will clear the codes) and then let the computer re-learn the driving codes. I know of people who have installed new part and still had the same symptoms and freaked out untill they cleared the computer and then all was well.


I didn't mean to write a book here. I hope this helps.

regards, Berry

 

Berry,

First off, Thank you for the quick reply. Secondly and more importantly, thank you for taking the time to be as thorough in your post as you were. I really appreciate all the info. I plan on tackling the troubleshooting phase of this tomorrow morning and I'll definitely post what I come up with as I go along.

Regarding some of the other items I listed, have any clue what the heck any of them might mean? Like for instance, "MIL Status"
What the.....?

or

"Readiness Monitors That Are Not Ready:
Catalyst"

I don't even understand the context of the sentence....

Just wondering

Thanks again,
Steve

 

Steve,
The acronym MIL is "Malfunction Indicator Lamp" or in Ford lingo "Check Engine Light" (CEL), both are synonomous. As I read the report, it is saying the CEL is on which causes your vehicle to automatically fail the test and the component identified is the the "catalyst". In reality, it is not the catalyst as they are mute items, but rather their reporting sentinels, the oxygen sensor(s). Your van is new enough that it may have two O2 sensors rather than the older models with a single O2 sensor. They generaly last around 100,000 miles, so yours is at the right age to be failing. The O2 sensor dies a slow death rather than keeling over all at once like other electronic components. 99 times out of 100, the problem is the upstream sensor. The downstream O2 sensor (the one at the rear of the catalytic converter) serves only to confirm the catalyst is operating properly. I would recommend replacing the upstream sensor. Prices for these sensors are all over the board but a decent one should run around $35-45. The local parts stores (Checker, AutoZone) also rent the special socket used to remove the O2 sensor. This a rather easy job on the Aerostar. While replacing the sensor, disconnect the negative battery terminal. After a 10 minute interval, the computer dumps the stored error codes. On restart, it takes about 10 minutes of driving time for the system to "relearn" your driving style and select the appropriate engine/drivetrain profile. In the interim, the van may seem to behave differently than before.

Before chasing down the evaporative emissions system, check your gas cap. Something as stupidly simple as a loose or non-sealing cap can elicit this code as well. Hope this helps.

 

The 02 sensor that checks the CAT is the one after the CAT.
The one before the CAT is the one that inputs for fuel mixture, etc.


Aero, am I right? I don't want to input bogus info here.

Oh yeah, the gas cap. It didn't happen to me, but a friend of mine had the the p1443 tying him in knots and it was a cracked cap.

I also know of people passing eyerything on smog only to fail because when they put the gas cap on the tester it leaked.

I shouldn't have forgotten that one.

 

I may be wrong here, but I believe systems with OBD-II have what they called a "Readiness Code," which must be on for a car to pass smog inspection. It's nothing more than the 10-minute run that Aerocolorado said, just so that the car can learn new parameters, particularly if one of the sensors have been replaced. Once it finished learning, the computer sets the readiness code and the car is ready for testing. Just to be sure, I'd take the car out on the freeway at 50-60 mph for about 20 minutes, and 10 minutes of city driving.

However, with gas as expensive as it is nowadays, just drive the car around for a couple of days and the readiness code will be set. The above procedure is for the case where you want to do a smog check right away.

As for the two codes, I think Berry and Dave have pretty much covered all possibilites. My brother's Explorer (4.0L) had the same codes and we took care of it just by replacing the O2 sensors. We did replace both, since we reasoned that if one went, the other is not far behind. At 100k miles, they are due for replacement anyways, and it really improves your mileage. But don't forget to check the hose and the canister valve as Berry said. They do crack often enough.

 

Thanks so much for the info you've all shared with me. I'm seeing that even if it's all of the things you've collectively listed, it's not going to put me in the poor-house in order to get it to pass emissions. In my previous reply, when I listed the errors listed on my results sheet I received from the emissions test station, I neglected to list 2 other items which were present. Under the heading "Bulb Check" it lists the following:
KEY ON ENGINE OFF/CRANKING: FAIL
KEY ON ENGINE RUNNING: FAIL

The only area which actually shows a passing result is the Gas Cap Test. Don't know if these added items make any difference but I'm sure one or all of you gentlemen will know.

Again, thanks to all for your wisdom and assistance with this.

Steve

 

Berry,
You are correct, the downstream O2 sensor is there simply as a monitor as to the efficiency of the catalytic converter. The O2 level in the upstream sensor provides data for the proper air/fuel mixture. As long as the downstream O2 sensor "sees" a lower O2 level coming out of the converter all is well. If the downstream O2 level approaches the same level as the upstream, then the converter is not working and an error code will be set.