In the fourth and fifth phases of China, in order to force the driver to repair after the fault is reported, the engine will limit the torque or speed limit (engine speed). However, in the sixth phase of China, a set of mandatory measures has been added, that is, the driver alarm system. In this phase, I will take you to have an in-depth understanding of the driver alarm system.
The purpose of the driver alarm system is to ensure the normal operation of the NOx emission control system as much as possible, especially the urea system, so as to ensure that the NOx emission can meet the requirements. In case of relevant faults of the NOx control system, the driver can be notified for maintenance in time.
According to the requirements of NOx control system, if it is detected that the reagent level is low, the reagent quality is abnormal, the reagent consumption is low, the injection of SCR system is interrupted, the EGR valve is stuck or the relevant sensor tampers with the fault, the driving performance limit system will be activated if it is not corrected in time. Before activating the driving restriction system, the driver warning system will notify the driver with a visual alarm.
The driver’s alarm system is a new requirement of national six, which requires a separate alarm system, which is different from and cannot be reused in OBD alarm or engine maintenance alarm. In other words, the driver warning system will have its own separate warning lamp.
At present, the six national regulations have extended the driving performance restriction system to the whole post-processing device, such as DPF, SCR, TWC and NSC. In other words, the driver warning system will be activated when the aftertreatment fails and the emission exceeds the OBD limit.
Tip: NSC system can not only absorb NOx, but also catalyze the reduction of HC, so doc can not be added after using NSC.
Driving performance restriction system: it includes two-level driving performance restriction system, namely primary driving performance restriction system and severe driving performance restriction system.
The primary driving performance limiting system reduces the maximum torque of the engine to 75% of the external characteristic torque of the engine. When the triggering conditions of the primary driving performance limiting system are met, the primary driving performance limiting system shall be activated immediately after the first stop of the vehicle.
Severe driving performance limits the vehicle running speed to 20km / h (grade mode). When the triggering conditions of severe driving performance limit system are met, it shall be activated immediately when the engine is started again of alarm system.
For the driver alarm system, the corresponding faults fall into 7 categories.
● blocked EGR valve
● interruption of urea injection system
● urea quality failure
● urea consumption deviation fault
● malfunction of the monitoring (tampering) float
● urea level low
● urea freeze in non heated SCR system
For the first five items, there are corresponding fault codes. The fault code corresponding to each item is actually used to explain the occurrence of such faults. For item 6, whether to trigger the driver alarm system is determined by the actual height of urea level. Item 7 is not actually used.
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The main function of EGR valve is to enter the exhaust gas into the combustion chamber, reduce the peak temperature of the combustion chamber, and then reduce the generation of NOx. Therefore, when the EGR valve fails, the NOx generation increases and the driver alarm system is activated.
When the driver warning system is activated and the engine continues to operate for 36 hours, if the stuck EGR valve fault is not repaired, the primary driving guidance system shall be activated and then activated according to the corresponding requirements. When the driver warning system is activated and the engine continues to operate for 100 hours, if the stuck EGR valve fault is not repaired, the severe driving guidance system shall be activated and then activated according to the corresponding requirements of alarm system.
The corresponding fault codes are as follows:
When urea injection is interrupted, NH3 cannot react with NOx, resulting in the increase of NOx discharged into the atmosphere and the activation of the driver alarm system.
When the driver warning system is activated and the engine continues to operate for 10 hours, if the action interruption fault of the urea nozzle is not repaired, the primary driving guidance system shall be activated and then activated according to the corresponding requirements.
When the driver warning system is activated and the engine continues to operate for 20 hours, if the action interruption fault of the urea nozzle is not repaired, the severe driving guidance system shall be activated and then activated according to the corresponding requirements.
The corresponding fault codes are as follows:
When the urea quality does not meet the standard (generally the concentration is too small), it will increase the NOx discharged into the atmosphere and activate the driver alarm system.
The driver warning system shall be activated in case of failure of relevant sensors of NOx control system and low conversion efficiency of emission after treatment devices (DPF, SCR, TWC, NSC).
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When the driver warning system is activated and the engine continues to operate for 36 hours, if the fault of the relevant sensor of the NOx control system is not repaired, the primary driving guidance system shall be activated and then activated according to the corresponding requirements.
When the driver warning system is activated and the engine continues to operate for 100 hours, if the fault of the relevant sensor of the NOx control system is not repaired, the severe driving guidance system shall be activated and then activated according to the corresponding requirements.
The corresponding fault codes are as follows:
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Read the national six driver alarm system, don’t worry about making no money!
There is no corresponding fault code for urea level fault in the driver alarm system, but the corresponding driver performance limit system is activated through the level information.
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This item is generally not used.
For driver performance limit activation, the following conditions need to be met:
1. General conditions for OBD monitoring: applicable to NOx and PM efficiency monitoring faults.
● ambient temperature – 7 to 38 ° C;
● altitude below 2500m;
● the engine cooling water temperature is higher than 70 ° C
If the monitoring requirements cannot be met, the driver warning system and driving performance limitation system will not be triggered
2. Other time-based faults that trigger the driver alarm system.
After the first five time-based faults occur, the warning system and primary driving performance limits and severe driving performance limits are shown in the figure below.
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3. Triggering the driver alarm system is based on a time fault.
Under any condition, as long as the urea liquid level is too low / empty, the torque and speed will be limited when the conditions are met.
When urea fault occurs, its warning system, primary driving performance limit and severe driving performance limit are shown in the figure below
The newly added national six driver warning system, when the severe driving performance limit is activated, the driving speed shall not exceed 20km / h, which will force the driver to repair. For this new speed limit logic and new fault phenomenon, only by mastering it in advance can we not be eliminated by the tide of “national six”.
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