Symptom: 2009 annual refine a commercial vehicle, the car assembling 2.8 L 4DA1-2B1 high pressure common rail diesel engine, a 5-speed manual transmission, mileage 19,000 km. The car odometer does not work due to my shop repair.
Check Analysis: Refine The car body structure to control electrical characteristics, resulting in possible factors are inoperative speedometer: speedometer failure itself, the back surface composition meter associated connector plug is not strong, and the vehicle speed sensor line fault, the driven gear damage the vehicle speed sensor, a vehicle speed sensor failure supply line, the vehicle body control unit BCM internal fault, the vehicle body control unit BCM line power failure, a failure inside the engine control unit and the body control module BCM and an engine control unit communication failure.
According to reflect the user, the car was in other shops replaced the vehicle speed sensor and the instrument cluster, but the fault persists, it is possible to exclude the possibility of damage to the instrumentation and the vehicle speed sensor. I use the lift car lift, turn the ignition key to ON block, made with a multimeter detects the vehicle speed sensor 3P power connector, the power supply is normal, the normal grounding line, but the speed signal line is at Ground state, It should be 5 ~ 6 V voltage under normal circumstances, and the vehicle speed sensor indicating a fault control signal line related to Ground.
Thus the author each investigation system associated with the line segment measurements. First, remove the battery holder located on the vehicle speed sensor and the end of the reverse lamp harness connector 4P, measurements (EE09 terminal No. 3 of the connector) with a multimeter its signal line, grounding is still in a state that the signal line to ground resistance to 76 Omega; left, then the internal BCM body control unit suspected fault is present. However, after starting the engine the car, the body open all electrical switches, the electrical work were normal, indicating that the presence of the vehicle body control unit BCM probability of failure is small. In order to verify whether the BCM body control module generates the fault effect on the instrument table I disconnect the control unit sets the lower left of the vehicle body 24P connector (white and gray), measured again for its signal line, the signal line which is still in the ride iron status, and the resistance to ground is almost unchanged, indicating that the body control module BCM signal line regardless of short to ground fault.
After checking the maintenance information that the author, the vehicle speed sensor signalLine not only in communication with BCM body control unit also communicates with an engine control unit which is connected to the engine control unit K75 terminal connectors. Disconnect the engine control unit 2 sets of connectors, the author found that a moist phenomenon internal connector, the terminal surface of the engine control unit and also traces of water. At this time, then the measurement of its signal line, the signal line is no longer shorted to ground, the voltage of the multimeter 5.6 V, normal.
Troubleshooting: I dry water traces connector surfaces an engine control unit with a hair gun, since the engine control unit is still under warranty period, replacement of a new engine control unit, will be refitted to the test parts removed , speedometer work properly. Troubleshooting After more than two months, the visit customers, failure does not reappear.
reviewed: car failure is mainly due to the engine control unit and its inlet connector, thereby causing an internal short circuit motor control unit, affecting the normal communication speed sensor signal line. As for the causes of the water, I found upon inspection not bad sealed case, and troubleshooting car does not appear before the phenomenon of water, thereby substantially exclude the possibility of external infiltration of water from the vehicle, the author analyzes the water should be caused by man (e.g., sprinkled into drinks).