Failure phenomenon: a 2009 BMW 750Li (F02) sedan, mileage 8 000 km. Say users, the car in normal driving, the sudden appearance of the instrument in high temperature engine icons and text prompts, along with ldquo; bang, bang rdquo; sound the alarm.
Check Analysis: after the vehicle into the plant, I did not find the engine temperature alarm. Thus connection failure diagnostic detection, the engine control unit stores the fault code 20A504 (turbocharger coolant pump control circuit breaker), no other fault code storage.
The high temperature engine failure is more common for the maintenance personnel, but the turbocharger coolant pump failure can cause the engine temperature is too high it? N63-type vehicle equipped with twin-turbo engine, an engine cooling system consists of two independent cooling system configuration (figures).
BRIEF
(1) wherein a cooling liquid circulating system for the engine coolant, the coolant radiator rarr; Thermostat rarr; Pump rarr; engine, by way of heat absorption effect of the booster pump coolant reaches the motor-assisted turbocharger exhaust gas allowed to cool, and finally to an engine inlet (front thermostat), another path through the auxiliary cooling system for an electric heater pump and valve rarr; heat exchanger rarr; engine inlet (rear thermostat).
(2) further cooling liquid circulating system for cooling the charge air, the cooling fluid under the action of the electric coolant pump, the coolant radiator from the turbocharger to the engine control unit in three columns each housing and the left and right supercharger cooler, back to the radiator absorbs heat.
The conventional exhaust gas turbocharger engine turned off, since the pump also will stop the operation, so can not be sufficiently reduced ldquo turbocharger; retention heat rdquo ;, the long run is likely to cause increased serious damage to the pressure. To solve this drawbacks, which the engine coolant pump auxiliary added, after the engine is stopped, the electric coolant pump can continue to operate the cooling liquid continues to circulate, to sufficiently heat the supercharger.
The control logic of the engine temperature alarmIt is a real-time engine outlet temperature sensor sensing the temperature of the engine outlet, and reported to the engine control unit, once the temperature limit is exceeded, the engine control unit will make the instrument sound and visual alarm signals. The fault code information of the car, if the motor-assisted turbocharger coolant pump fails, but can not sufficiently heat the turbocharger, this circulation system also has a mechanical cooling fluid pump of the main circulating main channel should be no problem, it it should not cause the coolant temperature is too high. Check the temperature of the engine while the vehicle is too high the alarm motor-assisted turbocharger coolant pump failure caused by, or caused by other reasons, the key to solve this failure.
does not appear due to a fault current, the first engine cooling system according to a rudimentary check previous maintenance experience. Coolant level and concentration of the normal, the radiator fan can be operated timely, the thermostat can be normally open. Then open the instrument service functions, call up the engine temperature display (the signal transmission path temperature displayed is: an engine outlet temperature sensor rarr; engine control unit rarr; PT-CANrarr; instrument, the signal transmission path and the temperature signal acquisition and engine temperature alarm is the same), and road test, during the road test frequently does occur in the engine temperature alarm, but the alarm is displayed by the instrument temperature 74 deg.] C, the temperature of the high temperature alarm engine is not seen too high.
Next troubleshooting codes should prompt the failure. Connection failure diagnostic, activate the turbocharger frequently coolant pump, the coolant pump can sometimes work and sometimes not work. Harness connector on the pump a total of three lines, are the power, ground and a signal line connected to the engine. Detecting the normal line, then replacement of the turbocharger coolant pump.
troubleshooting: After replacing the turbocharger coolant pump, no fault test engine temperature alarm occurs, a return visit after a period of time tracking, fault acknowledgment solve.
reviewed: So the actual temperature of the engine is not high, why would the police do? This is a concept vehicle of the decision. If there is no alarm at the high temperature was cooled turbocharger pump or line is damaged, the user will not service station to repair the vehicle can temporarily no abnormalities, but the turbocharger will work for a long time at a high temperature severeHeavy damage, so in order to avoid this consequence, regardless of the temperature of the engine is too high, as long as the engine control unit monitors the coolant pump to the turbocharger is not normal, alarm will be issued. Vehicle system is changing, control logic and design concepts are changing, so the repair can not be thinking, but repairs have to follow the idea of change.
(Xue Fei)