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Home Engine Mode $06 Diagnostic Update

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Most technicians who do engine diagnostic work today have heard of Mode $06, but many aren’t very familiar with what it is, how to find it, when to use or what to do with it. It’s still a mystery mode to many technicians.

Mode $06 has been around since the introduction of second-generation onboard diagnostic (OBD II) systems back in the mid-1990s. Essentially, Mode $06 is the raw test data the OBD II system uses to evaluate the operating status of various components in the engine management and emission control systems. If there’s a problem, the OBD II system will use the Mode $06 data to detect it and set a fault code. So think of it as the data behind the scene that eventually leads to fault codes being set.

Mode $06 is just one of the nine different diagnostic operating modes that are available in the OBD II self-diagnostic software. Each mode has a specific purpose or function when it communicates with a scan tool:


  • Mode $01 is used to request and display sensor data, open/closed loop status, whether switches are on or off, and any other data stream “PIDs” the system is capable of displaying.



  • Mode $02 is used to request “freeze-frame” data. This is stored information that is captured when a fault code is set. The data snapshot shows what was going on when the fault occurred, so it can help you figure out what might have caused the code to set.



  • Mode $03 is the one that lists fault codes stored in the PCM’s memory. These are the five-digit “P0XXX” generic OBD II codes and “P1XXX” OEM enhanced codes that are your starting point for further diagnostics. Codes don’t tell you what to replace, but they do tell you the nature of the fault and in what circuit or system it occurred.



  • Mode $04 is used to clear codes and freeze-frame data. It is also used to reset the non-continuous monitors.



  • Mode $05 is only accessible in higher-end scan tools, and is used to display oxygen sensor monitor test results. This mode is helpful for diagnosing O2 sensor problems, as well as air/fuel mixture problems.



  • Mode $06 is an advanced diagnostic mode that displays the unfiltered test results for all non-continuous monitors, which include the Evaporative Emission Control System (EVAP), catalytic converter, air system, PCV and EGR systems, engine thermostat, oxygen sensor, and engine misfires on Fords.


    Mode $06 is useful for diagnosing faults when the vehicle has an obvious emissions or driveability problem, but has not set any codes. It can also be used to spot pending problems that may soon set a code, a sort of crystal ball that allows you to foresee future codes. And, you can use it to verify repairs by making sure all the monitored systems are passing the OBD II diagnostic self-checks.


  • Mode $07 displays test results for all the continuous monitors, which includes misfires on vehicles other than Fords, the operation of the oxygen sensors, and the operation of all the engine’s sensors and other inputs. This mode tells you if the OBD II system has run all of its self-checks, and whether or not all of the monitors have passed (which is necessary for a vehicle to take and pass an OBD II plug-in emissions check).



  • Mode $08 is only available in professional-grade scan tools with bidirectional capability. This mode allows you to use your scan tool to run any self-tests that are available through the PCM. This includes things like turning the fuel pump on and off, cycling the engine cooling fan on and off, pulsing the fuel injectors, changing idle speed and so on.



  • Mode $09 is used to display vehicle information such as VIN, PCM calibration, etc.

Scan Tool Displays
The thing to remember about all of these modes is that they may or may not be labeled as such on your scan tool. Different scan tools display information differently. Some scan tools list the various modes and tell you what mode number the scan tool is in when it shows you data. Other scan tools skip the mode labels altogether and simply present the information by topic (fault codes, system data, freeze-frame, monitor status, etc.). The latter method is much less confusing and is a more user-friendly way of navigating all the data that can be displayed on the scan tool.


One reason why Mode $06 has been so confusing is that the information often has been buried under layers of menus, or has not been clearly labeled. If you don’t know how to display Mode $06, you’ll never find it, let alone use it. Fortunately, scan tool software continues to improve, making it easier to find Mode $06.

Finding Mode $06
Scanner software is constantly changing, and the latest software updates may be easier to navigate. Even so, here are a few examples of what you are going to run into with some scan tools when you go hunting for Mode $06 information.

On older Snap-on MT2500 scanners, for example, Mode $06 data is located by inserting the “Global OBDII” cartridge into the scanner, then selecting “OBD DIAGNOSE” after powering up the tool. Once communication has been established with the vehicle, you then scroll down the SELECT SERVICE menu to DISPLAY TEST PARAM./RESULTS and press “Y” (Yes) to continue. Then you choose NON-CONTINUOUSLY MONITORED SYSTEMS ($06). Then you can start looking at the various test IDs and results.

On the Snap-on SOLUS and MODUS, Mode $06 data is still under Generic OBDII, and NON-CONTINUOUSLY MONITORED SYSTEMS ($06) is still under the SELECT SERVICES menu.

On the OTC Genisys, open the Application Manager, choose Scan Diagnostics, then Global OBD II. On the next menu, choose Special Tests, then Component Parameters (Mode 6). You can now access the Mode $06 test information.

On a MasterTech scan tool, press F1 for SCANTEST when the Main Menu opens. When the FUNCTION MENU comes up, press F1 again. On the next menu, select GLOBAL OBDII. On the next menu, press F1 for OBD II FUNCTIONS. On the next menu, choose F5: SYSTEM TESTS. On the next menu, select F2: OTHER RESULTS. Still with me? Good, because you are almost there. The next screen lists the Mode $06 test information in three columns that are labeled TID$01, CID$01 and PASS/FAIL.

Deciphering Mode $06 Information
One of the problems with Mode $06 information that is displayed on many scan tools is that it is not clearly labeled as to what it means. If the scan tool software doesn’t tell you what a particular TID/CID stands for, or you don’t have a reference chart that identifies the TID/CID values for the year, make and model of vehicle you are attempting to diagnose, the Mode $06 information is pretty much useless.

On the MasterTech scan tool, for example, the first column is the “TID” or “Test Identification.” (Note: this is now called “MID” for Monitor ID on 2003 and newer vehicles with controller area network or CAN systems). Each line in the TID column stands for a different test. Next is the “CID” or “Component Identification” column, which is the specific component or circuit. The last column shows PASS or FAIL, indicating if the component passed or failed this particular test.

If all of the tests show PASS, you don’t really have to go beyond this point in most cases because everything is functioning within normal limits. Even so, one or more components may be borderline or just under the limit that would cause it to fail. Consequently, you may have to dig deeper to see what’s actually going on and what the actual numeric test values are for a particular test.

PASS means the test value is within the range allowed. In other words, the numeric value of the test is somewhere between a lower minimum limit and a maximum upper limit for that test. As long as the value remains within that range, it is assumed to be OK and passes the test. But if it goes beyond either limit, it fails the test and may eventually set a fault code, depending on the nature of the fault.

The limits for these tests are determined by the vehicle manufacturer when they test their emission control systems to find out how much leeway they have in meeting federal emission requirements. If they set the acceptable range for a particular test too wide or the upper limit too high, the vehicle may not meet emissions. On the other hand, if they set the range too narrow or the upper limit too low, the vehicle may be setting codes too often or when it does not really have an emissions problem.

Consequently, they choose limits that are broad enough to allow for some degradation and variation, but are narrow enough to trigger a fault code if the vehicle truly has an emissions problem. And if they don’t get it quite right and the vehicle sets a lot of false codes, they can change the limits with a PCM reflash.

An important point to keep in mind here is that some faults that cause noticeable driveability problems (like a lazy oxygen sensor or a slight misfire in one cylinder) may not be bad enough to set a code and turn on the Check Engine Light (which is required by law if a fault might cause emissions to exceed federal limits by 1.5 times). Likewise, some faults that may cause a vehicle to pollute may not cause any noticeable driveability problems (such as a bad catalyst, EGR problem or EVAP fuel vapor leak). Finding Mode $06 Information

If your scan tool only gives you the raw Mode $06 data and does not translate it for you, you’ll have to find a reference chart to decipher the information. One way to do this is to go to the vehicle manufacturer’s website and search through their service information for Mode $06 code lists (which will vary depending on the year/make/model of the vehicle). The information is not always easy to find, and some do not even publish any of their Mode $06 service information. Most OEM websites also charge a subscription fee to access their information. This is why many technicians don’t use Mode $06. It’s too much bother and takes too much effort to decipher it.

A fair amount of free Mode $06 information is available to members on the website. You can also go to John Forro’s website and subscribe to his extensive database of detailed Mode $06 information, much of which he has compiled himself from scanning various years, makes and models (and mileages) of vehicles. Forro’s data includes “normal” minimum and maximum values for many TIDs/CIDs, as well as typical values for higher mileage vehicles.

Raw Mode $06 data is in hexadecimal code, which is a base 16 numbering system used in computer programming. Hex code uses digits 0 through 9 and letters A through F. To translate a hex code number into a more familiar decimal number, you can use the calculator that comes with Windows software. Open the calculator, click on VIEW, then choose Scientific. Enter the hex code number in the calculator, then click on the “Dec” button to convert the hex code number to a decimal number. Example, hex code 28A becomes the number 600 in decimal.

What does the number mean? It depends on the test. It may be a voltage, amperage, temperature, pressure or whatever. This means the number may have to be multiplied by some conversion factor to end up with the correct units of measure. This kind of information would have to be looked up in a Mode $06 conversion chart for the vehicle.

General Motors’ $06 data definitions for GM vehicles using GMLAN diagnostic data link.

For a printable 12-page PDF copy of this document, e-mail Ed Sunkin at [email protected]

Fortunately, some scan tools and scanner software (such as the PC-based Auto Enginuity scanner) circumvents the need for reference charts and converting hex values to decimal equivalents by translating the Mode $06 information into plain English and familiar units of measurement for you. With the Auto Enginuity software, you open the folder named “On Board Test Results” to view Mode $06 data. All of the tests are clearly identified as to what they are, and the numeric test values for each are listed along with minimum and maximum limits, and the units of measure (volts, amps, pressure, etc.). This makes viewing Mode $06 data much simpler. The software also flags any values that are out of range, which is better than a PASS/FAIL indication because you can see how much a particular value is out of range. You can also see values that may be just within the limits, too, and may soon cause a fault code to set.

A Few More Mode $06 Tips
Some vehicles maintain the TID/CID data after the key has been turned off, but some (such as Ford) reset the TID/CID data when the engine is shut off. Consequently, you have to check the Mode $06 data before your turn off the engine following a test drive.

Misfire codes may take several trips to set. Using Mode $06 on a Ford to look at actual misfire counts can allow you to see how many misfires are actually occurring while the vehicle is being driven. In some cases, the engine may have a noticeable roughness, but it isn’t bad enough yet to set a misfire code. When some fault codes are set (like an oxygen sensor code), it can prevent other OBD II self-test monitors from running (like the catalyst monitor). The catalyst monitor needs good signals from all the oxygen sensors to compare the switching activity of the upstream and downstream oxygen sensors. If the downstream oxygen sensor is showing too much activity, it means catalyst efficiency has dropped. With Mode $06, you can look at these test values after replacing an oxygen sensor to make sure the converter is functioning within normal limits. This can prevent a code from setting later and a comeback if the converter is bad.

Mode $06 can also help you diagnose EVAP faults by looking at the raw data for the various EVAP tests the OBD II system runs on the vehicle. Some General Motors vehicles run up to 30 or more different EVAP tests. (See chart above.) If the vehicle keeps setting an EVAP code and you don’t know why, take a look at the EVAP Mode $06 tests to see what’s going on.

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Larry Carley

Larry Carley has more than 30 years of experience in the automotive aftermarket, including experience as an ASE-certified technician, and has won numerous awards for his articles. He has written 12 automotive-related books and developed automotive training software, available at
  • Greg

    Is a 98 chevy k1500 5.7 vortec compatible with mode 06 individual cylinder misfire counts?

  • randalusa

    Very helpful. Thanks mucho. I wanted to know capabilities of fairly cheap Snap-on tools at eBay (almost makes all them dopey keys worthwhile), especially Mode-06 and bi-directional. Now I do.

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