Four examples of car computer sleep state troubleshooting

November 27, 2019

Case 1: A 95-year Honda Accord sedan, F22B1 engine, hand gear, the owner reflected that the air conditioner did not work in the previous period, went to the repair shop for repair, it took more than a month, the air conditioner did not work. During the inspection, it was found that the radiator fan works as soon as the ignition switch is turned on; when the A/C switch is turned on, the diagnosis socket has a voltage of 12V on the ground, and other systems work normally. Then check the air conditioner-heater control panel and find that the circuit board has ablation. Someone added a line between the circuit board and the diagnostic socket ground, which is used for grounding. It is speculated that it may be that during the last repair, the repairman of the previous repair shop found that the A/C switch could not be grounded during the repair. It is also known that the black wire in the wire harness is the ground wire, so I grabbed a black wire to A. The /C switch is grounded. This black line is exactly the ECU diagnostic trigger ground wire. In this case, as soon as the air conditioner is turned on, 12V voltage is applied to the ECU. Over time, the ECU will be damaged, and the A15 pin cannot be grounded.

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Case 2: A Dodge 3.3L sedan, VIN code is 2B3ED46T4RH207004 (the air conditioning system is consistent with Dodge Jielong), due to the failure of the air conditioning system into the repair shop, the repairman of the factory is to test whether the compressor works, without disconnecting the system. Next, blindly send a 12V voltage to the pressure switch. The air conditioner failed to try out, and the car did not come (the car entered the "computer sleep state"). We went to the detailed inquiry of the repairman's operation process, and then measured the signals of each system. It was found that the six fuel injection solenoid valves controlled by the PCM were not grounded, and the fault self-diagnosis system did not work. There was no start code No. 11 and end code No. 55 ( The system diagnostic seat is the first generation of the ALDL six-terminal socket used by Chrysler's CCD and LH engines. The multimeter is used to measure the diagnostic seat. The signal output is high. The 6th grounding terminal has a 6.5Ω resistance, which is basically determined to be PCM burned. After replacing the new PCM, the system resumes normal control and repairs the air conditioner.

The above is an example of a passive "computer sleep state" that ends with a replacement ECM.

Case 3: A 92-year-old Lincoln City sedan started normally, and the low-speed driving was normal, but the speed could only reach 60km/h, the exhaust pipe was black smoke, and the fuel economy was worse. Upon inspection, the water temperature sensor (ECT) is faulty and can only be maintained at a low temperature fixed value (10000fl). Because EEC-1V (Ford's fourth-generation powertrain electronic control device) sets the fault code and starts the "faulty operation mode", there are certain conditions, and the ECT sensor value is within the calibration range, so EEC-1V detection No sensor failure, no "fault operation mode" support, only that the vehicle operating state has been in the first 10 seconds after the low temperature start, on the one hand, the injector is continuously enriched, on the other hand, EEC-1V will not control A/ T enters the fourth gear action. We call this phenomenon "active computer hibernation." In essence, due to insufficient information data, EEC-1V generates calculation errors, which leads to control errors, causing some systems to fail to work properly.

Case 4: The ABS system is an important device for vehicle safety. Its manufacturing and maintenance requirements are very high. Some high-end car ABS systems, such as the TEVES MKII 55-pin ABSMOD, are pre-loaded with two sets of data. Compared with the returned signal, as long as one signal is wrong, ABsMOD will exit the work, shut down the system and change to normal brake. The fault light will be illuminated at this time, but there is no "faulty operating mode" support. Sometimes ABSMOD will also quit working just because of the battery voltage. We also summarize this phenomenon as the "computer sleep state" of ABsMoD.

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