Driving mileage: 62 miles

Issue: The car's keyless entry function is invalid.

 Diagnosis: The vehicle is new. When doing PDI, the maintenance professional discovered that the system had a fault code: “B117113 enters and starts the system antenna in the bumper is open, static," which was deleted after the fault code was removed. When testing the four-door keyless entry function, the door lock function was working, but on the second day, the customer reported the failure again.

 After the technician picks up the car and turns on the ignition switch, the instrument displays "Fault: Keyless System". The fault code is still B117113.

 The entry and start-up system antenna in the rear bumper still has an open circuit. Examine the KESSY system of the car's structure next. The KESSY system control unit J965 is mounted in the passenger side instrument panel. The system has a total of 8 antennas: 3 indoors are R138/R139/R137, 4 exterior door handles and 4 antennas EX6/EX7/EX8/EX9, and the antenna R136 is located within the rear bumper. The 4 antennae, as well as the antenna and the sensor, are built within them. The four antenna plugs are all four wires, with two wires for antennae and two wires for sensors. Through the ELSPO system, the antenna wires are all connected to J965. According to the fault code analyze the meaning of, and the cause of the fault is based on the principle of easy first and then difficult, which means that: R136 is damaged, the line connection is faulty, and J965 is faulty.

 The following is a step-by-step investigation according to possible causes.

 The follow-up maintenance is relatively simple. The final fault point is that the R136 antenna is damaged. However, due to some mistakes in the process of replacing the R136, the circuit was checked successively, J965 was replaced, and the R136 was finally replaced.

We learned that after placing the car into the starting system interface J965, needs to be matched with J965. This is comparable to how anti-theft components are matched. Before the match is successful, the ignition switch cannot be turned on. As a result, only the double flashing lights or intermittently turning on the dimmer switch are necessary to prevent the anti-theft system from going to sleep and initiating the diagnostic program for matching, as per conventional anti-theft component matching. However, it becomes stuck in an unending loop while matching J965. The initial page, under normal circumstances, select the diagnosis on the right navigation bar of and then follow the diagnostic tool page step by step. Although some control units may not be recognized, they can enter the anti-theft matching page. However, the car is caught in an endless loop. When entering the start module page, the diagnostic instrument will always prompt to turn on the ignition switch but before J965 is not matched, the ignition switch cannot be turned on anyway, so this leads to a dead end. If you try to short-circuit the No. 15 terminal at this time, and artificially turn on the ignition switch to continue matching, it will display FAZ9113S again. Obtain a description of the FAZ9113S fault in the 5th generation anti-theft matching from Volkswagen's VW after-sales service technical information system, and explicitly mention that one of the possible causes of the issue is a problem with powering off the line 15. This demonstrates that short-circuiting terminal 15 artificially is not possible. After several efforts, it was discovered that selecting self-diagnosis from the right-hand navigation bar did not identify the system control units one by one and instead went straight to the network topology diagram page. Then choose the 00B7 controller, and the match is complete. This is indeed a big difference from the previous matching steps, and this is the first harvest in the car matching process.

 The second phenomenon, and the one that caused the author to question his earlier assumptions, is that the car's R136 is damaged (disconnect the plug immediately), the error code can be removed, and the trunk should not be opened using the keyless function when the door is locked. The error code will never reappear. Use the keyless function to operate the four doors or start at this moment; otherwise, the function will have no impact. The instrument will only prompt the keyless entry system failure if the door is locked and the trunk is opened using the trunk handle button; if the four-door handle is disengaged for any purpose, the keyless system will fail instantly, which leads to the following points:

 (1) The 5 antennas outside the car, EX6/EX7/EX8/EX9 and R136 have very different fault levels and functions. The 4 door handles have a high priority for faults. Any damage to the system will immediately remember the fault and enter without key. The complete failure of the function also affects the keyless start function.

 After R136 is damaged, it only affects the keyless opening function of the trunk. When this function is not used, J965 cannot detect the working status of R136 at all, and has no effect on other J965 systems, as if it is independent of the J965 system.

 (2) The relationship between R136 and J965: R136 actively sends signals to J965, while J965 can only passively receive signals sent by R136. Under normal circumstances, after the vehicle locks the door, bring the key close to the trunk and press the trunk opening switch by hand. The opening process at this time is: ① Press the trunk switch to activate and wake up the body module; ② The body module is awakened through its low-frequency antenna and then send a low-frequency signal to the key and wake up J965 at the same time; ③ After the key is activated by the low-frequency signal, it sends a high-frequency signal (key ID) to J965 through R136; ④ J965 informs the body module of the key information through the CAN line; If the key is legal, an instruction is issued to control the opening of the trunk.

 (3) Since every link in the above-mentioned opening procedure is interlocked, how does J965 detect the R136 open circuit logic? There are two fault circumstances in the process of unlocking the trunk: R136 open circuit or unlawful key. Both faults have a detection time that begins when the key is activated and emits a high-frequency signal. The key is sent if R136 is open. The high-frequency signal of J965 cannot be received by J965, so J965 determines that R136 is disconnected; if it is an illegal key, the illegal key ID signal received by J965 through R136 is checked as illegal by the body module, and it is displayed on the instrument display as: no key, indicating that it is an illegal key; and if it is an illegal key, the illegal key ID signal received by J965 through R136 is checked as illegal by the body module, and it is displayed on the instrument display as: no key, indicating that the key is illegal or no key signal.

 (4) The role of the three antennas R137/R138/R139 in the car. The three antennas are higher in level than the four-door antenna, any one of them damaged will seriously affect the keyless start function, and also affect the keyless entry function. But why is there one in front of the gear lever, one in the rear seat position, and one in the trunk?

 The main purpose is that the legal key can be identified at any position in the car, and it will not affect the normal start of the vehicle. In other words, even if the key is placed in the trunk, the driver can still start the vehicle without any influence.

 Finally, let's discuss the keyless entry system's disable feature. This function is the same as the vehicle control module's sleep function. If the keyless entry system is not used for an extended period of time, the vehicle's door handle capacitive sensor will be disabled. The keyless entry function for the passenger door is disabled for more than 60 hours, and it is re-enabled when all three of the following conditions are met: keyless entry through the driver's door or the trunk flap, pressing the button on the remote control to control the vehicle, and mechanically unlocking the vehicle. For the main driver's door, the keyless entry function will be disabled only after 90h. The conditions for re-enablement are to operate the vehicle by remote control and unlock the vehicle mechanically.