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How to Access Mode $06 Diagnostic Data

What is the Mode $06 Diagnostic?

Part of a vehicle’s Onboard Diagnostic II (OBD II) system, Mode $06 is one of the 10 modes of the OBD II system that monitors emission control components and other systems and sensors. Containing a wealth of information that you don’t see in live readings, the data generated in Mode $06 can lead you to seeing issues before they trigger a hard fault and can give clues to the condition of systems that are degrading. 

Originally, Mode $06 data wasn’t meant to be used by technicians, it was behind-the-scenes information used to make up the OBD II monitoring of various emission systems in which Pass or Fail test results could lead to the illumination of the Check Engine light. This was a requirement by the EPA for vehicle manufacturers beginning in 1996. While many older scan tools lack the capability of accessing and displaying Mode $06 data, as time went on, technicians found that Mode $06 had useful diagnostic information.

How Can Mode $06 Help Technicians?

The data generated from Mode $06 monitoring can help technicians:

  • Detect problems before they set off an error code.
  • Determine if a Diagnostic Trouble Code (DTC) was triggered by a system failure or if the test barely failed.
  • Verify that repairs that have been made have corrected the problem without having to wait for OBDII tests to run and illuminate the Check Engine light.

About Mode $06

Supported in generic OBD II, Mode $06:

  • Displays test results of non-continuous monitors.
  • Displays test results for some continuous monitors.
  • Breaks down monitors to individual tests that make up the complete system monitor.
  • Test value shown is for the last test completed.

Non-continuous monitors require that certain conditions are met before a test is run. This type of monitor can cause people to think that a problem is intermittent. Just because the MIL stays off for a week or more doesn’t mean that the problem is intermittent if it is monitored non-continuously. Many non-continuous monitors are two trip monitors and until certain conditions are met, the monitor will not complete. Until complete, a pass or fail cannot be generated.

While continuous monitors are constantly running, they may not necessarily set a code as soon as a component malfunctions. The system must meet a set of criteria before triggering a fault.

It is important to remember that in this mode you can’t ask the computer to run the tests; rather it is pulling the data from the most recent tests that is stored in the computer’s memory.

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What Does Mode $06 Monitor?

Continuous Monitoring:

  • Misfire
  • Fuel system
  • Comprehensive component
  • Thermostat 
  • PCV

Non-Continuous Monitoring:

  • EGR system/variable valve timing
  • AIR injection system
  • Evaporative Emissions
  • Oxygen sensor
  • Oxygen sensor heater
  • Catalytic converter

The information that this monitoring gives can help resolve issues like:

  • Reducing catalytic converter comebacks
  • No-code drivability and emission faults
  • Engine misfires
  • Identifying systems and components that are close to failure
  • EGR & EVAP repairs

What Does the $ Mean?

The $ in Mode $06 signifies that the data is presented in hexadecimal (hex) code rather than ordinary numbers. The hex numbering system is based on 16 instead of 10 which allows more information to be placed in a smaller space using less memory and computing power. The maximum number value that can be obtained is 65535. Remember this number because a vehicle’s computer commonly uses this number as a default value for when something is not working or not completed. Because the data is in hex code, it needs to be translated for it to be useful. Many scan tools will do the translation for you.

How Does Mode $06 Data Display on a Scan Tool?

Mode $06 data displays differently on a scan tool than other types of readings. 

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TID = Test Identification Data

CID = Component Identification Data

MID = Monitor Identification Data (CAN only)

TLT = Test Limit Type

Using the above example, it is easy to see that the data isn’t presented in a straightforward manner. To know what the name of the test and the part that is involved, it’s necessary to ascertain the Test Identification Data (TID) and the Component Identification Data (CID). To find that information, you’ll need to find the reference chart from the vehicle manufacturer that lists what test each line of code refers to and the range of values that are acceptable. You can often find this information online with a search.

How to Access Mode $06 from a Scan Tool

Mode $06 can be accessed from the generic or enhanced side of the scan tool. When using the enhanced option, navigate to Generic Functions where you’ll see Mode $06 On-Board Monitored Systems. Once you open that menu, you’ll see all the areas being monitored. 

You can then select a specific test to view. Please note that it is not a live reading, this is a test result based on the last time the test was run. To know exactly what the test is measuring and how to interpret the results, you’ll likely need the manufacturer reference chart to decipher the information given.

How Mode $06 Can Help Diagnose Exhaust Issues

The data from the tests found in Mode $06 can help you find the root cause of issues with several systems including the catalytic converter and exhaust system. There are three tests that are of particular interest:

  • Switch ratio
  • Oxygen storage capacity
  • Integrated air/fuel method

Learn how to use these tests to diagnose exhaust system problems and reduce customer comebacks.


Learn more about quality exhaust parts, find the right car part, or find a local repair shop today.

The content in this article is for informational purposes only. You should consult with a certified technician or mechanic if you have questions relating to any of the topics covered herein. Tenneco will not be liable for any loss or damage caused by your reliance on any content.

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