Misfire Diagnosis Using Mode $06 (Advanced) - Taurus Car Club of America : Ford Taurus Forum
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post #1 of 15 (permalink) Old 03-07-2013, 10:57 AM Thread Starter
Sam
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Misfire Diagnosis Using Mode $06 (Advanced)

Written by me, re-written by/coauthored with behlinla
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This guide is written for ADVANCED USERS ONLY who would like to get the most out of their scan tools. You should have gotten here from the misfire guide, so read through that first if you haven't already.

If you're experiencing a very slight misfire or a misfire that only shows up under certain conditions, it can sometimes be frustrating trying to locate the source of the misfire if you don't have any trouble codes (maybe because somebody cleared them before you got to look at the car). Or perhaps you're stuck with only a P0300 or P0316 code that doesn't give you any cylinder specific information either.

If you're in one of these situations, luckily Ford vehicles with OBD-II have a special cylinder-specific misfire count available inside part of the OBD-II specification called mode $06. Modes are just different sections of the OBD-II specification (SAE J1979) that deal with different functions. For example, stored DTCs are handled by mode $03, and freeze frame data is found in mode $02 (most scan tools rename the modes with their function so they're easier to use). Mode $06 is used to display specific test results used as part of the emissions monitors. For example, you can see the fuel tank pressure changes in all the stages of the evaporative emissions monitor (EVAP). Documentation for all the data you see in mode $06 is available from the Motorcraft Service website (download the PDF for your model year): http://bit.ly/10AY0gN

To read mode $06 data, you will need a fully ELM327-compatible scan tool and software that supports mode $06. Note that most ELM327 scan tools found online for less than $20 are clones that probably do not support mode $06 properly.

I am using a device called OBDLink SX and the software that came packaged with it, OBDWiz. This particular scan tool is wired (USB interface), but there are also other options available that are both cheaper (e.g. ElmScan 5 Compact) and that support wireless connectivity (e.g. OBDLink MX).

More info on scan tools: https://www.taurusclub.com/forum/124-...uld-i-buy.html
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Okay, on to the real task! Mode $06 diagnosis. If you plug your scan tool into your OBD port and open OBDWiz, after connecting, you can go to the left side and click "Monitors". At the top you see several options. Click the "On-Board Monitoring" tab, and you should see the mode $06 data display after the scan tool polls the PCM. Note there is a refresh button at the top which you may want to use periodically while driving to update the data.



On the left you see a list of TID's (Test ID) and component IDs. These are used to reference the specific test result you want to find. In the center you see the current value, as well as the min and max thresholds for the test. Finally you see a pass/fail flag on the right depending if the value falls within the acceptable range. Again, if you want to know what all these numbers mean take a look at the OBD operation guide for your model year (see above).

In general, TID's $50-$56 seem to be related to misfire monitoring on all vehicles. TID $56 seems to always be potential misfire events.

Cylinder-specific misfire rates are found under one of the following TIDs depending on your model year:
$51 - 1996-1997 MY
$53 - 1997-2006 MY
$81 - 2007+ (CAN bus)

I have a 2000 Sable, so my results are found under TID $53. You can see there are six component IDs ($01-$06) under TID $53 that correspond to each cylinder (a V8 would have eight obviously). If no misfires are occurring, you may only see one or two values show up rather than all six. I am not sure how often the data is reset or what period of time it represents.

Here is how we interpret this data. According to the OBD-II guide for the 2000 model year, I found that we can get the percent of the time that the cylinder is misfiring by multiplying the value for each cylinder by 0.000015. 2000MY OBD-II Guide: http://bit.ly/Z21MOY

So if you look back at the picture you notice that my cylinder #6 has a reading of 108. Do the math and we get that cylinder #6 is misfiring 0.00162% of the time. That would mean the computer detects it misfiring 16.2 times per 1,000,000 revolutions of the crankshaft. Now that doesn't seem like a lot, but in reality this number is probably much higher because the PCM can't positively detect all misfires.

If we do the same math with the max threshold (20224), we can see that the PCM will set a misfire code when the misfire percentage reaches 0.303%. That's 3000 misfires in 1 million revs.

Look at the picture again and notice the value for TID $56 and the maximum threshold. I have obviously failed this test! These are potential misfire events. An event is any disruption in crankshaft acceleration, which can be caused by going over bumps in the road, the A/C compressor clutch engaging, or even just because of noise in the crankshaft signal. In order to count as a misfire, an event has to occur during a misfire check and have a certain acceleration profile, so the vast majority of events are not considered misfires (even if they are being caused by one). If more than a certain number of events (3000 in my case) are logged in a certain period of time (every key cycle) the PCM will do a 1000 rev misfire test to find out if the car is truly misfiring, and what cylinder/how often it is misfiring. This can only happen after the crankshaft profile correction portion of the misfire monitor has completed. Profile correction monitors crankshaft acceleration during a fuel-cutoff deceleration to "learn" the exact tooth profile on the crank position wheel. After a KAM reset or code clearing it requires you to coast (no brake) from 60-40mph 3 times to complete the monitor.

There are several other misfire-related TIDs that are displayed as well. For the 2000MY, $54 is the percent of misfires that are catalyst damaging. If this number gets above the threshold it will activate the flashing CEL. $55 is the percent of misfires over the threshold for acceptable emissions. When this number gets above a certain number it will set a misfire code and illuminate the CEL. $50 is the total misfire rate for all cylinders combined. So what the computer actually reads as true misfires will pop up here as a percent. It's updated every 1000 revolutions (so it will read 0 except when your car misfires within the same 1000 revolutions of the crankshaft).

How can I use these numbers to solve my misfire problem?

The most useful value(s) in mode $06 are going to be the cylinder specific misfire rates under TID $53. If you see a value above zero for one or more cylinders, it's probably worth doing some more thorough checks on the coil, spark plug, injector, gaskets, or compression that corresponds to that particular cylinder. Seeing a very low number there (under 100) is not a great cause for concern, but you will probably notice the engine running rough at times, or perhaps the misfire will get worse with time. Either way, you should use mode $06 in combination with other scan tool data (DTCs, fuel trims, freeze frame data) to get a complete picture.

NOTE (thank you Jeff K): It is normal to see a very small number of misfires accumulate on all cylinders even with a motor that is running perfectly. Do not panic and start swapping parts because you see a number of potential misfire events with no symptoms. This is completely normal for a healthy motor - even a brand new car may show some. Keep in mind that after doing the math, these percentages are TINY unless you have a cylinder badly misfiring (which you will notice and will set a CEL!). Most of the time you should wait until the CEL illuminates to find the actual problem that exists.

In the case of my Sable, troubleshooting is ongoing. I've already tried swapping the #6 coil with a spare I have with no change in the cylinder #6 misfire rate in mode $06. I'll update this topic if I find the exact problem. I never figured it out since I ended up selling the car. I have a misfire at cold startup with my 2008 which doesn't even show up in mode $06! So nothing to do about it but wait.

Sam

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Last edited by Sam; 03-12-2013 at 10:55 AM.
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post #2 of 15 (permalink) Old 03-12-2013, 08:32 AM Thread Starter
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I believe this is completed. Thank you behlinla!

Sam

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post #3 of 15 (permalink) Old 03-12-2013, 10:46 AM
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Looks great, Sam! Only thing I would expand upon is that it is perfectly normal to see a very small number of missfires accumulate on all cylinders even with a perfectly running engine. I know you kind of mentioned this, but some people may freak out seeing some missfires slowly accumulate on all cylinders.

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post #4 of 15 (permalink) Old 03-12-2013, 10:51 AM Thread Starter
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Wasn't just me, thank behlinla too! His idea to actually write it up, and he is the only reason that it actually is comprehensible! I did the first ROUGH, rough draft though.

You are talking about in $56, right? Potential events, or are you talking cylinder specific?

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post #5 of 15 (permalink) Old 03-14-2013, 02:52 AM
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I think this was a great idea. I had my surprise when I noticed these on my screen. And I think with this software getting more specific, more people will want to know about it. Maybe this should be a sticky.

I just remembered, In OBDwiz you can also create a custom dashboard indicator that can monitor each cylinder for a misfire as well.
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post #6 of 15 (permalink) Old 05-29-2014, 11:43 PM
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Here the mode 06 info for different model years FoMoCo:

http://www.motorcraftservice.com/vdi...&menuIndex1=10

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post #7 of 15 (permalink) Old 05-30-2014, 03:48 PM
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Quote:
Originally Posted by xmanglc View Post
Here the mode 06 info for different model years FoMoCo:

http://www.motorcraftservice.com/vdi...&menuIndex1=10
Link is taking me to the main motorcraft service page. Maybe you have to be logged in there.

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post #8 of 15 (permalink) Old 05-30-2014, 04:34 PM
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Try rhis:
http://www.motorcraftservice.com/vdi...&menuIndex1=10

If it still takes you to the front page click on theory and operation...

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post #9 of 15 (permalink) Old 06-01-2014, 04:18 PM
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Quote:
Originally Posted by Jeff K View Post
Looks great, Sam! Only thing I would expand upon is that it is perfectly normal to see a very small number of missfires accumulate on all cylinders even with a perfectly running engine. I know you kind of mentioned this, but some people may freak out seeing some missfires slowly accumulate on all cylinders.
I would have to disagree.

What you are describing is a random misfire across all cylinders - I am going to say this is not normal or acceptable. Even if it does not ultimately trigger a CEL.

Not trying to argue - but I have not seen this on a properly working (or new) vehicle.

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post #10 of 15 (permalink) Old 06-02-2014, 09:53 AM
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Is Forscan be able to read the $06 data?

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