Description Of Taking A Readout Of Extended Diagnostic Trouble Code (DTC) Information
CONTENTS
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STATUS IDENTIFIER, DESCRIPTION
| Status identifier |
| There are different status identifiers that can be read off for each diagnostic trouble code (DTC). The control module tests each terminal almost continuously. By reading off the diagnostic trouble code (DTC) and the associated status identifier (which detects the fault and stores the DTC), information about the test is obtained. Not all status identifiers need to be implemented in one control module. This varies from system to system. All status identifiers are reset and start counting again each time the control module is powered up and when erasing diagnostic trouble codes (DTCs). The possible status identifiers are described below. |
| Status identifier | Explanation |
| Upper graph | When the signal value is above or below a maximum or minimum value that is considered to be a fault by the control module, an instantaneous fault is registered (i.e. a fault is active). The value may vary depending on the specific diagnostic trouble code (DTC). Examples of this are U > 11.5 V, U < 2 V or f < 10 Hz. |
| SI#01 (see the graph) | The test is active. The control module can only detect faults and store diagnostic trouble codes (DTC) when the test is running. |
| SI#02 (see the graph) | The test has been active. Indicates whether the control module was able to detect faults and store diagnostic trouble codes (DTC). |
| SI#03 (see the graph) | The control module detects an instantaneous fault. This information is used by the control module to determine if or when a diagnostic trouble code (DTC) should be stored. As soon as a signal exceeds the permitted value (compare with the upper graph), there is an instantaneous fault. |
| SI#04 (see the graph) | The control module has detected an instantaneous fault. An instantaneous fault has been detected at some stage. |
| SI#05 | Lamp lighting / Text message. Information about whether the diagnostic trouble code (DTC) activates a warning lamp or text message in the combined instrument panel. |
| SI#06 | The test is disabled because another fault has occurred. The diagnostic trouble code (DTC) is stored at the point of the base fault. If this leads to further faults, related diagnostic trouble codes (DTCs) are not stored. |
| SI#08 (see the graph) | Counter for instantaneous faults. When an instantaneous fault is detected by the control module, a counter counts up for as long as the fault exists. When the fault is no longer present, the counter counts down again. The diagnostic trouble code (DTC) is stored in the car if the counter reaches a certain maximum value. The maximum value varies between different diagnostic trouble codes (DTCs). The speed of the count depends on how long the fault can persist before it results in customer symptoms. |
| SI#09 (see the graph) | Maximum value of counter SI#08. There are a variety of ways that the counter value for instantaneous faults can be read off depending on how often the diagnostic has been run. |
| Lower graph | Validating diagnostic trouble codes (DTCs). The diagnostic trouble code (DTC) is stored when the counter for instantaneous faults has reached its maximum value. |
COUNTERS, DESCRIPTION
| Counter |
| A useful fault-tracing tool is the Diagnostic Trouble Code (DTC) counter. The control module stores 6 different counters for each Diagnostic Trouble Code (DTC), which describes the occurrence. The counters can be used to determine when and how often a fault has been detected. Using the counters for the Diagnostic Trouble Code (DTC) it is possible to see if the fault has only been registered during the current operating cycle or whether it has been detected previously. If a fault is intermittent it is possible to determine how intermittent the fault is by studying the values of the different counters. Example:
In the examples given above, counter 1 gives the number of operating cycles where the diagnostic was run without a fault being detected. Counting takes place from when the fault was last detected. Counter 3 is the total number of operating cycles regardless of whether the diagnostic was run or not. Counter 4 shows the number of operating cycles where the diagnostic detected a fault. Counters 3 and 4 start to count from the first operating cycle after the operating cycle when the fault was first detected. In the example, counter 4 = 1, which means that the fault was detected twice. One can see that no fault was detected during the relevant operating cycle. Depending on the number of operating cycles and the customer's driving pattern, it can assist in ruling out this control module from the customer's current problems. The counters can help us understand how intermittent the fault can be. If the counters 1 = 0, 3 = 0 and 4 = 0 it indicates that there have not been any operating cycles since the fault was detected and that the fault was probably generated in the workshop. For an operating cycle to be recognized certain requirements may be necessary, for example, increasing the engine coolant temperature. In certain cases ignition on, ignition off and ignition on again are counted as an operating cycle. Counter 5 can be useful if the fault was detected in this operating cycle. The time can be used to determine more exactly when the fault occurred.
NOTE:
Not all counters need be implemented in a control module, this varies from system to system. The possible counters are described below. |
| Counter | Function |
| A (see the graph) Counter 1 |
The graph illustrates the time at which a fault occurs. In the illustration the control module has detected a fault in the second cycle. This fault has then occurred a total of 5 times. The counter can be read off for each diagnostic trouble code (DTC) in the control module in which this is implemented. Operating cycles are marked with vertical lines. An operating cycle usually begins at ignition on and finishes when the ignition is switched off. |
| C#1 (see the graph) Counter 2 |
Counts the number of operating cycles since the fault was last
validated. This information can be used to determine whether the fault is active during the current operating cycle or not. The fault is present now if the value is zero. This counter is also used for most systems to give "Permanent fault" and " Intermittent fault" text messages in VIDA when reading off a diagnostic trouble code (DTC). |
| C#3 (see the graph) Counter 3 |
Counts the number of operating cycles since the fault was first
validated. When a fault has been validated, the counter will count up by 1 for each subsequent operating cycle. The same as counter C#1 but monitors the number of cycles since the first fault occurred. |
| C#4 (see the graph) Counter 4 |
Counts the number of operating cycles in which the fault was validated since it was first validated. Counts the number of times the fault has occurred since the first time. |
| C#5 Counter 5 |
The counter assesses the number of seconds the control module has been operating since the fault was first validated and the diagnostic trouble code (DTC) was stored. The time the control module has been operating is only counted when it is active, not in "sleep mode". |
| C#6 Counter 6 |
The counter assesses the number of seconds the test (the diagnosis) has been operating since the fault was first validated and the diagnostic trouble code (DTC) was stored. |
| C#7 Counter 7 |
The counter assesses the number of seconds the fault has been valid since it was first validated and the diagnostic trouble code (DTC) was stored. |