Advanced Automotive Fault Diagnosis
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LÔØI NOÙI ÑAÀU, ledklok
- Điều hướng trang này:
- Start End
- Cruise control systems diagnostic chart
| 9.17.2 Components and circuit
The main components of a basic air bag system are as follows: ● driver and passenger air bags; ● warning light; ● passenger seat switches; ● pyrotechnic inflater; Electrical systems 241 Hand and eye checks (loose wires, loose switches and other obvious faults) – all connections clean and tight Check battery – must be 70% charged Start End Fuse continuity – check voltage at both sides with a meter or a test lamp Check the ignition supply voltage to the ECU – battery voltage. Check the earth wire – 0 ⍀ to a known good earth Operation of the control and power switches (voltage same in and out) Check road speed sensor output – may be the same one for the speedometer is a good signal? Check mechanical fitting is correct Check same signal reaches ECU Yes No Renew sensor Continuity of wiring to throttle actuator Throttle actuator resistance or operation checks The system can be ‘road tested’ on a secure wheel free ramp to check operation Cruise control systems diagnostic chart ● igniter; ● crash sensor(s); ● ECU. The air bag is made of a nylon fabric with a coat- ing on the inside. Prior to inflation the air bag is folded up under suitable padding which has spe- cially designed break lines built in. Holes are pro- vided in the side of the air bag to allow rapid deflation after deployment. The driver’s air has a volume of about 60 litres and the passenger air bag about 160 litres. Figure 9.63 shows a steering wheel with an air bag fitted in the centre. A warning light is used as part of the system monitoring circuit. This gives an indication of a potential malfunction and is an important part of the circuit. Some manufacturers use two bulbs for added reliability. Consideration is being given to the use of a seat switch on the passenger side to prevent deployment when not occupied. This may be more appropriate to side-impact air bags. The pyrotechnic inflater and the igniter can be considered together. The inflater in the case of the driver is located in the centre of the steering wheel. It contains a number of fuel tablets in a combustion chamber. The igniter consists of charged capaci- tors, which produce the ignition spark. The fuel tablets burn very rapidly and produce a given quantity of nitrogen gas at a given pressure. This gas is forced into the air bag through a filter and the bag inflates breaking through the padding in the wheel centre. After deployment a small amount of sodium hydroxide will be present in the air bag and vehicle interior. Personal protection equipment must be used when removing the old system and cleaning the vehicle interior. The crash sensor can take a number of forms; these can be described as mechanical or electronic. The mechanical system works by a spring holding tải về 7.07 Mb. Chia sẻ với bạn bè của bạn:
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