Advanced Automotive Fault Diagnosis
tải về 7.07 Mb. Chế độ xem pdf
|
LÔØI NOÙI ÑAÀU, ledklok
| 10.4.6 ECAT fault diagnosis
Carrying out a test on an electronically con- trolled automatic transmission (ECAT) is like any other ‘black box’ system. As discussed pre- viously, do consider all the mechanical aspects of the system before looking for electrical faults. Looking at the ECAT block diagram (Figure 10.11) it can be seen that the system can be con- sidered as a series of inputs and outputs. Many of the sensors (inputs) can be tested using normal equipment such as a scope or multimeter. The difficulty is often that the sensors and actuator are not easily accessible. Figure 10.12 shows an electrohydraulic valve block, sensors and ECU combines and illustrates this quite well. The diagnostic link is almost essential for diag- nosing these systems. Of course if the complete unit is replaced then the fault will more than likely be fixed – as long as it was an electrical problem of course! A typical test procedure for an ECAT would be as follows. 1. Check fluid condition and level. 2. Check for leaks. 3. Look for other symptoms on the vehicle (an engine problem may be connected). 4. Road test and check operation of all gears. 5. Pressure test the system pump pressure*. 6. Pressure test the converter pressure*. 7. Interrogate fault codes if possible. 8. Check as indicated by the DTC. Transmission systems 257 Figure 10.10 Transmission pressure testing 9. Carry out a stall test. 10. Check sensor signals using a scope. 11. Check sensors such as control switches. 12. Check resistance of solenoid actuators. The above list is very generic but will serve as a useful reminder of the process. *When carrying out pressure testing, manu- facturers data is essential. However, as a guide the following figures are typical. Selector Gear Rev/min Bar position (approx.) (approx.) Pump D 1 800 7 2, 3, 4 4000 5 (as per the system) R R 700–4000 12 Converter D 4 With clutch 0.7 max (or top) locked tải về 7.07 Mb. Chia sẻ với bạn bè của bạn:
|