13.2.2. The HHT device for testing of the electronic equipment of the car
The tester of NNT (Hand-Held-Tester) allows to find and check quickly and precisely malfunctions of electronic systems. In model of the E-class a large number of such systems with a possibility of diagnostics – from ABS before climate control is established. The controller of each system is connected to the diagnostic socket which is in a motor compartment. By means of the device at the station diagnostics can be carried out at detection of malfunctions, during repair, by transfer of the car to the owner or at trial trips. Pressing of the button activates the program of check which is written down in the replaceable test module. The malfunctions of this or that electronic system found during express check then can be in details analysed during detailed diagnostic checks. The cause of defect is displayed on the display of the device.
From controllers of electronic systems there can be schitana also those malfunctions which arose during operation, but by the time of check at the station externally are not shown. Thus, it is possible to obtain information on the latent defects. In memory also power setting or the car when this or that malfunction was recorded remains. If malfunction happens repeatedly, electronic devices fix specifications at the first and last emergence, and also consider repetition frequency.
Controllers are equipped with the emergency programs which allow to work to system even at failure, for example one sensor. Some of these electronic systems function so harmoniously that the driver can not notice malfunction emergence even.