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Old 06-13-2019, 12:07 PM
EchoRanger EchoRanger is offline
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Default How to solve incomplete emission monitor issues

Good afternoon,

I decided to make a new forum post regarding a few emissions related issues I ran into a while back.
My hope is that if any other Ranger, or Explorer owners run into a similar issue, this post will help them begin to troubleshoot their vehicle; however, I will warn potential readers that this will be a long and drawn-out post.

To start with, this write up is of a 2002 Ford Ranger XLT 4.0L V6 with an automatic transmission, and California Emission equipment. Here in California, we have to smog our post 1975 gasoline vehicles every other year. Typically, smog checks run around $50 - $60. Last January, I took my vehicle in for a routine smog check (like I do every 2 years). I failed the smog check. Not because my Check engine light was on, or because I had any codes stored in the computer. I failed emissions because a few of my emission monitors were incomplete. At first, I recalled disconnecting my battery a week or two before in order to work on my vehicle. Thinking this was the issue, I took the invoice informing me of my failure (still had to pay) and I drove my ranger several miles to try to get the emission monitors to finally complete. No luck.

This went on for several months. I paid the California DMV $50 for a month long smog extension. I was only able to purchase 2 months worth of extensions from the Cali DMV. Fortunately, I drive other vehicles and I was still able to get back and forth to work and do daily driving. But, in order to verify any work or repairs I did to the ranger, I had to drive it. Eventually I did so Ė with incomplete registration. I am very fortunate to have not been pulled over in that time frame. Anyways, I went online to several forums, including this one prior to membership, and I tried to search a few different threads in hopes of finding a few hints here and there. Every thread I was finding basically said that the vehicle just needed to be driven, in accordance with the drive cycle procedure, so that the monitors would complete. So, I did just that. I drove my ranger 500 Ė 1000 miles, in accordance with Fordís drive cycle procedure, with no results. No change in my monitor status. Still incomplete.

At this point, I knew this was an issue of failure whether mechanical or electrical, versus just needing to drive the vehicle more. So, I decided to look into the mode 6 data that was on the ECU. OBD 2 requires there to be 9 different modes, each representing a separate category of test data. For those reading this who are unfamiliar with Mode 6, it is essentially the computerís stored test results and other components and system monitoring. As the computer is running its own self tests on the various systems on the vehicle, the vehicle stores these results. Mode 6 is where the ECU stores the results for these self tests. I have a few OBD 2 scan tools, but the only one I have that has this feature is my blue driver blue tooth scanner (this is an outstanding scan tool that is used in conjunction with your smart phone via app). After doing a few resets of the ECU and monitoring system (disconnecting battery/reconnecting) I was ending up with the same Mode 6 test ID numbers every time. The test ID numbers are displayed in the chart below:





Now, as I mentioned at the beginning of this post, this issue happened last January (2018) much of the data I have is from hand written notes. Some of the incomplete monitors I was having are missing because they soon completed after my initial note taking, so I didnít bother writing them ALL down. Also, all of the incomplete tests soon completed after a short drive. Something to note if you are attempting to retrieve mode 6 data from your Ford product Ė Ford has made their mode 6 data proprietary, therefore most, if not all, scan tool manufacturers will be unable to provide the user of said scan tool any explanation along with the test and ID number. You must look this information up online. Initially, when I was retrieving the mode 6 data, all I was getting was a message next to each line item that said something to the effect of, ďunable to display results.Ē I ended up emailing the customer support team over at blue driver and asked them why I wasnít able to read the codesí definition. They emailed me back promptly and told me about the proprietary nature of Fordís mode 6 data and sent me a PDF link. The PDF link he sent me was an official bulletin released by Ford that explained each Mode 6 test and definition. As can be seen from the chart, all of the evidence is pointing toward an evaporation emission issue. The ECU was unable to complete the evap monitor pressurization tests on the entire evap system as they had all failed. In order to establish a fault and trigger a fault code, the ECU must be able to, at a minimum, complete itís routine emission monitor tests. So, I began with a visual inspection of the evap lines Ė under the truck along the chassis, under the bed near the fuel tank, and in the engine bay. I soon started to find a couple of dry-rotted emission hoses.


A photo of the dry-rotted hose:




This was one of the first culprits. This is a tank vapor line that travels to the purge valve solenoid in the engine bay. It was located on top of the fuel sending unit.

Here is a photo of the new hose in place:



Apart from the hose being reduced to no more than dust, in the photo where the end of my pen is, you can see a decent sized hole. Initially, I thought this was clearly the reasoning behind the incomplete monitor issue I was having. So, I replaced the hose with a brand new hose and took the ranger for a test drive. I went for a 50 mile drive abiding religiously by Fordís drive cycle procedure. Surely, this hose must have been the keystone issue behind my rangerís incomplete monitors. Wrong. Once again, the ranger still had incomplete monitors. During my first inspections, I noticed a few other rotten hoses, though not nearly as rotten as the first. I decided to replace those hoses as well.

A photo of the tank to purge valve solenoid hose that comes off of the steel evap line that runs along chassis:




As you can see, this hose is pretty badly dry-rotted (Dry rot is quite common when you live in the Mojave desert, one of the hottest locations on earth) Though, not nearly as bad as the first hose I found. Though this hose appeared to not leak and it did hold air pressure, I decided to go ahead and replace it anyway.





Here is another view:








On the purge valve solenoid going to the engine, I found yet another dry-rotted hose:




This hose wasnít as badly rotted as the rest. After replacing all of these hoses, I decided to go for another test drive. This time I drove nearly 100 miles, abiding by the Ford drive cycle procedure. Once again, no change in the emission monitor status. I decided to look into the evap pressure sensor, which is located on the chassis adjacent to the fuel tank. Unfortunately, inspecting this sensor required dropping the fuel tank. So, I figured while Iíve got the fuel tank removed, I might as well replace any and all fuel hoses and evap hoses that might be on the verge of needing to be replaced. And, while the time is convenient, test the pressure sensor and the vent valve solenoid.
The vent valve solenoid, located on the charcoal canister, appeared to have a good coil when ohm-ed out:




One more component to check off the list. Moving on to the evap pressure sensor. As I mentioned earlier, this sensor is located inline with the EVAP hoses and is mounted on the chassis. The EVAP pressure sensor is a 3 wire sensor. Ground, 5-volt reference, and a return. I used a multimeter with pushpins to backprobe the connector to check all three pins of the sensor. The sensor was receiving its 5 volt reference and ground, but I read nothing at all for the return wire. Measuring the resistance between the return wire and ground wire, I was reading open loop (OL). I had finally found my incomplete monitor issue. I do wish I had taken more photos of this entire troubleshooting saga, But I was more concerned about resolving the issue and being able to once again legally drive my ranger. I did not take any photos of my faulty EVAP pressure sensor or any of my testing thereof, unfortunately. After replacing the EVAP pressure sensor, my monitors completed within 5 mins of driving

Here is a photo of the EVAP pressure sensor (new) that I found online. It comes with everything you need to replace the tubing and solve your emission issue:



I do hope that you all enjoyed reading this. I also hope that it may help someone in a similar position as I was. The truck now has complete registration and I continue to drive it to this day. The entire process took about 4 months to solve.








Here is a screenshot of the complete monitor status on my scantool:





Best of luck to everyone!!!
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  #2  
Old 06-13-2019, 01:16 PM
CalebJ CalebJ is offline
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Default Re: How to solve incomplete emission monitor issues

Great work on the troubleshooting, and likewise on sharing your notes about the process.
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Old 06-13-2019, 04:34 PM
turismolover22 turismolover22 is offline
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Default Re: How to solve incomplete emission monitor issues

Good Job.

I've found that, even though we don't want to, it's best practice to replace all the lines when you find at least one that's dry rotted. Follows the same procedure as the brake lines when they burst.
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