To Decide The Intensity Of A Malfunction
Examples 1-5 (below) are based on counters for diagnostic concept Generic Global Diagnostic (GGD).
When a malfunction is intermittent or has unknown status, the diagnostic trouble code's counter is very useful to decide:
- How many driving cycles that have passed since the malfunction was detected the first time as well as since the malfunction was detected.
- During how many driving cycles that the control module has detected the malfunction during a certain period, as well as how many driving cycles that the control module has not detected the malfunction. That the control module has not detected the malfunction may be due to the control module not having started the test for the malfunction, conditions to detect the malfunction are not fulfilled, or that the malfunction no longer exists.
The purpose of interpreting the counters is that it is possible to understand the malfunction's intensity, that is, show "how much" intermittent the malfunction is, as well as help in assessing if the chances to repeat the malfunction and customer symptom, and then succeed with troubleshooting.
If you read out the diagnostic trouble code information and it shows that the diagnostic trouble code test runs at least once every driving cycle (e. g., when driving), the counters' value may be very important when assessing the diagnostic trouble code's status and actions. However, if start of diagnostic trouble code test and its conditions are difficult to achieve, the counters' values should be considered to be of less importance.
Counters 1 and 3 show driving cycles. Counters 2 and 4 also show driving cycles, but then really a "share" of counters 1 and 3, respectively. In principle, counter 4 shows how many times that the customer should have detected symptoms.
For systems with diagnostic concept Generic Global Diagnostics (GGD). If many diagnostic trouble codes are stored at the same time, then certain diagnostic trouble codes (the oldest) will have these frozen values/counters erased, this to save memory in the control module. These diagnostic trouble codes will then only have counter 2 left. Note also that counter 2 will also be erased when the memory is full, but often later than when other counters are erased.
For system with diagnostic concept Volvo Diagnostics II. If many diagnostic trouble codes are stored at the same time, the control module keeps at least half of the oldest and half of the newest diagnostic trouble codes in the trouble code memory.
For diagnostic trouble codes where the malfunction is not detected for many driving cycles and where the malfunction is detected again, then frozen values and counter values are written over with new values, that is, the diagnostic trouble code is considered "new".
Example 1, Intermittent malfunction
- Counter 1 = 5
- Counter 2 = 2
- Counter 3 = 25
- Counter 4 = 10
- Driving cycles
After the malfunction has been detected for the first time (driving cycle 0) the malfunction has been detected again in 9 of the first 20 driving cycles. Using this, the conclusion can be drawn that in 11 driving cycles the test has not been run or the malfunction has not been found, or a combination of these. After the last time that the malfunction was detected, 5 driving cycles have passed, where the test was run in 2 driving cycles without detecting a malfunction.
Conclusion: Intermittent malfunction
Assessment: Good possibility to repeat the malfunction and customer symptom, and thus succeed with troubleshooting, as the malfunction has been found quite recently in several driving cycles.
Example 2, Permanent malfunction
- Counter 1 = 0
- Counter 2 = 0
- Counter 3 = 25
- Counter 4 = 26
- Driving cycles
After the malfunction has been detected for the first time the malfunction has been detected again in all following driving cycles.
Conclusion: Permanent malfunction
Assessment: Very good possibility to repeat the customer symptom and thus succeed with troubleshooting, as the malfunction has been found in every driving cycle. Since the malfunction has been detected during the present driving cycle it does not really matter for troubleshooting if the malfunction has been detected in all previous driving cycles or not.
The counter show more how "sure" the malfunction is as well as that it can confirm if the customer experienced the malfunction as the counter indicates.
Example 3, Intermittent malfunction
- Counter 1 = 122
- Counter 2 = 122
- Counter 3 = 125
- Counter 4 = 4
- Driving cycles
After the malfunction has been detected for the first time the malfunction has been detected again in the 3 following driving cycles. After the last time that the malfunction was detected, 122 driving cycles have passed, where the test has been run in 122 driving cycles without detecting a malfunction.
Conclusion: Intermittent malfunction
Assessment: Not very good chance to repeat the malfunction and the customer symptom and thus succeed with troubleshooting, as the malfunction has only been detected in a few driving cycles a very long time ago.
The less driving cycles a malfunction has been detected in and the greater the number of driving cycles since the malfunction was detected the last time, the more difficult it is expected to be to repeat the malfunction and the customer symptom and thus succeed with troubleshooting.
This can be read off by the lower value is on counter 4 and the higher the value is on counter 1 and 2, as well as the lower the difference is between the value on counter 3 and counter 2, the more difficult it is expected to be to repeat the malfunction and the customer symptom and thus succeed with troubleshooting.
Example 4, Intermittent malfunction
- Counter 1 = 25
- Counter 2 = 25
- Counter 3 = 25
- Counter 4 = 1
- Driving cycles
After the malfunction has been detected for the first time, the malfunction has never been detected again. After the last time that the malfunction was detected, 25 driving cycles have passed, where the test has run in 25 driving cycles without detecting a malfunction.
Conclusion: Intermittent malfunction
Assessment: Not very good chance to repeat the malfunction and the customer symptom and thus succeed with troubleshooting, as the malfunction has only been detected in one driving cycle quite a long time ago.
Example 5 Unknown status
- Counter 1 = 25
- Counter 2 = 0
- Counter 3 = 25
- Counter 4 = 1
- Driving cycles
After the malfunction has been detected for the first time, the malfunction has never been tested and/or detected. After the last time that the malfunction was detected, 25 driving cycles have passed where the test has not been started. Since the diagnostic trouble code test has not started anymore, it cannot be decided if the malfunction exists or not.
Conclusion: Unknown status
Assessment: Read diagnostic trouble code information and try to achieve condition so that the diagnostic trouble code test is started and run, which makes it possible to detect the malfunction. If the malfunction is detected, chances are very good to repeat the customer symptom, and thus succeed with troubleshooting when the malfunction has been found in the current driving cycle.
If the malfunction was not detected even though conditions are fulfilled, then chances are less good to repeat the customer symptom, and thus succeed with troubleshooting as the malfunction has not been found in the current driving cycle.