A mileage over 200,000 km, Configuration 1 MZ-FE engine and automatic transmission A540E Lexus ES300 sedan. Users reflect : the shift lever into the D position, the vehicle can not move forward, only to slam on the accelerator pedal travel . When the vehicle is running , the engine speed reaches 3000r/min speed super, but more than 120km / h, the dashboard malfunction lights.
After the pick-up : the use of diagnostic self- diagnosis , there are two fault codes : P0753 and P1765. Meaning fault code P0753 is the shift solenoid valve A circuit fault ; fault code P1765 is the meaning of the accumulator pressure control solenoid valve failure . Analysis of fault codes reasons , there may be line solenoid valve itself is bad or bad . Unplug the solenoid valve harness connector , check the terminal solid, no oxidation. Check the lines and found no abnormalities. The total of four automatic transmission solenoid valve , respectively, shift solenoid valve A, shift solenoid valve B, the lockup clutch solenoid valve, pressure control solenoid valve. Measure the resistance of two shift valves are about 14Ω, normal . Clear DTCs, road test , normal fault light goes out . Stopped vehicles, the shift lever from P bit to L -bit moves back and forth several times, engine fault lights , while O / D indicator flashes. Taking of fault codes, fault codes P0753 and still P1765. Disconnect the engine and transmission control unit harness connector , BMW ICOM measure the resistance of the solenoid valve 4 in the wiring harness plugs, were normal.
Solenoid valve using an oscilloscope to detect the probe in the pressure control solenoid valve control signal line idle condition signal voltage is 11 ~ 13V, and the fluctuation waveform approximate a straight line. Depress the brake pedal , the shift lever into the D position, and then release the accelerator pedal is depressed , the signal waveform is unchanged , indicating that the engine and transmission control unit does not issue commands to adjust the shift . Using the same method to detect the shift solenoid valve A , found that the solenoid valve has been powered down. In D1 file start , shift solenoid valve A should energized under normal conditions. The above findings explain poor performance of the engine and transmission control units . Remove the control unit , it was discovered internal circuit board corrosion, some copper wire is tripped , two Launch scan tool capacitors have leakage phenomenon . Repair circuit boards, replacement of damaged capacitors installed engine and transmission control units. Road test to confirm the fault completely ruled out.
Engine and transmission control unit uses the duty cycle signal to the pressure control solenoid valve , the solenoid valve to change the hydraulic pressure acting on the back of t300 key programmer the accumulator , so that smooth shifting process , the duty ratio signal with gear changes. Vehicle starting ( 1 file ) when the shift solenoid valve A should be energized , and the corresponding oil passages open , shift solenoid valve B should be off , and the corresponding oil channel is closed. If two shift solenoid valves are off , then start the equivalent of a file in 4th gear ( overdrive ) started driving the vehicle difficult .