General Motors Mode 6 Data CLICK HERE.
OBD II Monitor Data
The on-board diagnostic monitors responsible for triggering check engine light codes encompass a number of smaller tests. These tests are executed by the vehicle’s computers and yield a pass or fail result. The logic is such that rarely will one failed test result in the given monitor requesting illumination of the check engine light. For a control module’s logic to fail the monitor entirely it must deem the results of the smaller tests to be statistically significant. These failure thresholds employed by the different computer modules contain very sophisticated programming responsible for processing the results of a number of smaller tests in a logical manner. Once this logic determines that the statistically filtered test result performance is degraded past a failure threshold, it will store a Diagnostic Trouble Code (DTC) in the respective module.
Mode $06 Classifications
There are two classifications contained in the monitors that are executed by the vehicle’s computer:
- Test Identifiers (TIDs) – This Hex value identifies the respective Monitor. They may also be referred to as MIDs on CAN OBDII systems.
- Component Identifiers (CIDs) – These Hex values indicate the parts of each monitor. Note: on CAN OBDII systems where the test identifiers are referred to as MIDs the component are TIDs.
A professional grade of Scan Tool can request/receive the results of these smaller tests and convey their results to the technician.
Mode $06 Diagnostic Value
Vehicle control modules are encoded with sophisticated logic that filters and processes results in a manner consistent with fundamental statistical methods. This high-level logic prevents a DTC from being stored until a pre-programmed threshold is surmounted. The increased visibility into the vehicle’s systems provided by Mode $06 data is invaluable for technicians. A tangible understanding of the categories and sub-tests will enable a professional technician to effectively and efficiently diagnose some of the most challenging intermittent check engine light issues. With enough training and experience it is possible for an expert diagnostician to identify a degraded component prior to failure of a system Monitor and subsequent CEL request.
Mode $06 Limitations
Due to ambient conditions and uncontrollable operating variables it is normal for TIDs and CIDs to fail at one point or another. Logged failures do not necessarily indicate a degraded component or real fault. Failures of tests assigned a low statistical weighting are temporarily stored until the control module is satisfied by the response of further tests. Replacing components by Mode $06 data alone undermines the logic of the control module. Using this data without proper training and experience can result in unnecessary repairs being performed. Moreover, effectively utilization of Mode $06 data can be time consuming. Incorporating it into the diagnostic process takes experience and understanding of the vehicle’s systems. It is important to remember that this data may be incorrect if codes or the vehicle’s memory was recently cleared.
For an intermittent check engine light the Mode $06 results will indicate a test that is near a failure threshold. On CAN vehicles regulations require misfire data too be supported by Mode $06. Thus, if a Scan Tool does not contain Misfire PIDs the Mode $06 data can be used to calculate misfire percentages per cylinder. Additionally, it is easier to identify the cylinder responsible for a P0300 using this data. It is important to understand both the enabling criteria and fault criteria for the particular code being diagnosed. A hard-fault can appear intermittent because mechanical or ambient conditions are not appropriate for the control module’s logic logic to enable the test.