Fault phenomenon
    A Honda Accord 2.4L passenger car, mileage of 26,000 km. After the start of the engine shift lever in the P block can not move.
    Fault diagnosis and analysis
    There is a gear lock switch at the bottom of the automatic transmission shift lever. Through the brake switch signal input to the transmission control unit so that the gear switch work, open the lock switch lock channel, transmission shift lever to move.
    First check the brake switch, when the brake pedal after the brake light, and use the Honda special detector to detect the transmission control unit inside the brake pedal signal, indicating that the brake switch work well.
    Then check the transmission control unit and gear lock solenoid valve and its line, are working properly. With the Honda special detector did not detect the fault code; read the data flow to find the engine idling value of 1000r / min. This vehicle uses a mechanical throttle and a spool-type idling motor. When the idling speed of the engine is higher than the standard idling and the idling motor is not self-learning, the control unit of the engine does not send a signal to the gear lock solenoid valve (transmission Control unit and ECU is a control unit), resulting in shift lever can not move. I cleaned the throttle and idle motor, and the control unit format (self-learning), troubleshooting.
    Maintenance summary
    As the modern engines are high-speed engines, and some cities often traffic jams, as well as the quality of oil problems, resulting in engine fuel can not be fully burned, resulting in throttle, idling motor and so easy to dirty, should always be cleaned to ensure that the car work properly.
Expert reviews
    For the Honda Accord the above fault does exist, and is a very common kind of failure, the cause of the failure generally have four aspects:
    First, automatic transmission shift lever lock mechanism itself failure;
    The second is the brake light switch and line fault;
    Third, the throttle position sensor (throttle body assembly) damage, resulting in throttle position sensor idle signal voltage is too high;
    Fourth, the idle control valve (IAC) dirty, stuck in the opening position.
    The first and second reason, the majority of maintenance personnel can think of, and can quickly troubleshooting. The first reason to remove the automatic transmission shift lever to lock the structure itself, the mechanical or line problems can be solved. The second reason to remove the brake light switch and line problems can be resolved. The third and fourth reasons many maintenance personnel can not understand, in the maintenance is also more difficult to think, so in particular to illustrate.
    For the third reason, if the throttle position sensor (throttle body assembly) is damaged, causing the engine idling operation, the TPS signal voltage is greater than 0.5V (individual case TPS value equal to 0.5V). Because the actual operation if the TPS value is greater than 0.5V, ECM will default at this time the engine is not in the idle state, then shift will be dangerous, but also on the engine and automatic transmission life have an impact, so ECM does not give shift lock solenoid valve Signal, so that it does not work, resulting in the shift lever can not be removed from the P position. The problem typically requires replacing the throttle body assembly and resetting the ECM / PCM learning values.
    For the fourth reason, when the idle control valve (IAC) is dirty, stuck in the open position, the idle air compensation when the air into the more, then the IAC valve command is not the current slide valve opening required Of the instructions, too much idle air compensation, resulting in the engine speed from the idle speed of 750r / min increased to 1200r / min or more, this time the fuel injection time is not the current requirements of the fuel injection time, then the throttle position is closed And the engine temperature is also at the normal temperature. These correct sensor parameters are compared with the incorrect sensor parameters due to the slip of the spool valve and compared with the ECM / PCM memory (ROM) cure reference data. The ECM / PCM is calculated by Out of a conclusion, that is, the engine is not running at idle conditions. But the actual situation is indeed in idle mode mode, but the engine speed in the idling conditions exceptionally increased. ECM / PCM will compare the parameters of the conclusions (error parameter data) to learn. (9%), that is, ECM / PCM that the throttle position sensor at this time is in the correct closing position on the opening (10%) on the benchmark and then open the default 9% Of the position, but does not meet the idling conditions of 10% of the opening, so the memory relative to 9% of the opening value, which starts the engine and automatic transmission protection mode, the shift lever lock.