Maintenance knowledge: examples of Jetta car maintenance

Maintenance knowledge: Jettacar repairMaintenance example
Trouble phenomenon: left front doorCentral lockswitch, The locking is normal, but the unlocking is not.
Fault diagnosis and elimination: According to experience, this kind of fault phenomenon is mostly switch orRelayFailure, so the replacement repair method was adopted, the left front door central lock power window switch was replaced, and the central lock power window relay under the instrument was replaced regardless of
use. In the end, it is judged as a line failure. According to the circuit diagram, there are only two wires from the driver's central lock switch E150 to the central lock control unit J379, the yellow wire controls the lock and the gray-black wire controls the unlock, and these two wires are in the circuit. There is no plug connection. Use the on-off gear of the multimeter to directly measure the on-off from the No. 2 pin of the central lock switch E150 to the No. 8 pin of the central lock control unit J379. The result shows a disconnection, so the central lock control unit J379 cannot receive the central lock switch. E150 unlock signal.
The left front doorWire harnessUnplug it from the central relay and check for open circuits. It is found that one part of the wiring harness at the door hinge is worn out. After the wiring harness is repaired, the fault is eliminated.
Model: GIX new interior
Trouble phenomenon:ABSThe fault lamp alarmed, and the maintenance worker diagnosed that the ABS electronically controlled hydraulic unit was faulty, and the fault remained after the replacement.
Fault diagnosis and troubleshooting: ABS alarms when the car comes for repairs. The maintenance worker displays a fault code of 01276 after diagnosis with VAG1551. The content of the fault code is that the V64 signal of the ABS hydraulic pump is open to the positive electrode, due to the ABS electronically controlled hydraulic unit of the Jetta. There were many faults, so the maintenance worker did not think much, and replaced the ABS electronically controlled hydraulic unit, but the ABS fault light still alarmed, and there was a fault code of 01276. The Jetta ABS system has two 30A fuses, which are placed horizontally above the central relay box. One of them is powered by the ABS hydraulic pump V64 alone. Is this fault fuse broken? So check the 30A fuse above the central relay box, one of them was not inserted. After inserting one fuse, VAG1551 was used to clear the fault memory, and the ABS fault light went out.
Model: GIX new interior optimization wiring harness
Trouble phenomenon: The AC switch is on when the air conditioner is turned on when the blower switch is turned to the first gear, and the air conditioner is working, and then the blower switch is turned to the second, third, or fourth gear, the AC switch indicator light goes out, sometimes the AC switch indicator light flashes Bright,compressordisconnect.
Fault diagnosis and troubleshooting:
Analyze the fault according to the circuit diagram. The fault point should be the wiring harness from the blower switch to the AC switch. Remove the air conditioner panel and unplug the blower switch. When the wiring harness shakes, smoke suddenly emerges from behind the meter, indicating that the wiring has a worn ground. The place. Remove the battery pile head and check the wiring behind the instrument. It is found that the wiring harness after the blower switch is in contact with the metal bracket of the instrument panel. The long-term vibration wiring harness is worn out and the ground is worn. Fix the wiring harness after repairing, and troubleshooting. The wiring harness behind the blower of many new interior cars is very tight, which can easily cause such failures.