Bmw Inability To Speed Up The Sluggish Start Transmission Failure Instance

Bmw Inability To Speed Up The Sluggish Start Transmission Failure Instance

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A 1993 BMW 525i sedan produce, equipment E34 engine, driving 250,000 km. A vehicle started the recent weakness, poor acceleration of failure, the owner open to my shop.
I pick up after the first X431 read fault codes, first check the engine failure, showed no fault codes; check the transmission failure, the display "brake solenoid valve with a" fault code; clear fault codes after the test, the vehicle started strong, accelerated fast response, can speed up to 180kmh, the owner is very satisfied. The car that has been repaired, I did not realize when they turn off and then start when the fault occurs, read the fault code is still "the brake solenoid valve with a" clear the fault code and then changed for the better, but stalled after the start failure and relapse.
According to test the fault code, first check the transmission wiring harness, no damage, corrosion, have good contact of each plug. As I repair BMW is not much, but no detailed information, can not accurately find the brake with solenoid valve, decided to open the transmission oil pan inspection, after some analysis to find the brake with solenoid valve, there is a black line and a blue line and its phase, measure the resistance is 13, check the connection to the transmission ECU (position in the right cab A-pillar) of 45 feet and 54 feet, also found no grounding, the phenomenon of virtual access. Also check the other line, no problem. By the way clean up the transmission oil filter and oil pan, installed after filling fuel required, and the original test found the same fault.
Test, the inference is based on the phenomenon of transmission failures into fail-safe state, has been working in the 2 block. Think about the previous experience of maintenance of transmission, and open book look up fail-safe transmission of the main reasons is that transmission TCU, throttle position sensor, speed sensor, the sensor input shaft, shift lock solenoid and solenoid valve. Based on the above ideas gradually examination ruled out the throttle position sensor, the sensor input shaft and locking solenoid valve may be faulty. Proceeded to check the speed sensor, the waveform analysis with the X431, the standard matrix square wave, no clutter, which in turn eliminates the speed sensor is suspect. TCU is generally a bad transmission is not easy, so again focus on the shift solenoid valve, to find information that "part of the car as long as a shift solenoid valve failure, the solenoid valve to stop all work into the fail-safe mode, the car in the forward direction Only 2 files. " Since the detection of fault code is "brake solenoid valve with a" must have its reasons. And open the transmission oil pan, check all lines of solenoid valves, solenoid valves found in the car is under positive control, static checks no problem, decided to use seven light-emitting diodes, each line in parallel with a solenoid valve, in motion Check. The comparison found that the transmission into fail-safe mode, all LED lights. Is it faulty transmission of the TCU? Open the computer found by the transmission, built a small shift solenoid valve control relay positive, with X431 relay consumer codes work this look, turn off and then turn the ignition key is not working.
There is a computer malfunction or other reasons? In order to find the cause of the malfunction, the author has made a test of the solenoid valve, the lock solenoid resistance found for the 5 , and the previously measured values are very different, why is it so? Even if the temperature does not change so much. Little change in other electromagnetic valve measurement. The thinking seems to lock solenoid is a major factor in failure, decided to change a solenoid valve installed after the elimination of the fault code, repeated testing, failure made no appear.

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