Failure phenomenon: a 2003 annual BMW E65 730Li sedan, equipped with N52 engine. Say users, start the car the car in the morning, after the coolant temperature rises opens the hot air, but there is no hot-air blowing, and then after a while the high temperature alarm occurs, ldquo appears on the display screen I-drive; engine temperature is too high, stop operation of the engine rdquo; tips.
Check Analysis: open the engine cover, the engine can be seen that indeed high temperature coolant discharged from the filler opening. Touch down pipes, the water feels hot water cool down, as if the thermostat is not turned on. Connection failure diagnostic, fault code reading engine system, the system stores ldquo; 2E84 electric cooling fan communication failure rdquo ;, read engine coolant temperature of 103 deg.] C, but reads the temperature of the water 63 ℃, it can be seen up and down great water temperature difference. The reason maintenance experience, such a big temperature difference between the upper and lower pipe phenomenon is not circulating coolant, a radiator and a thermostat including clogging does not turn on and the like. Clear DTC test, long after the fault is no longer present, but in the back of the factory and no way to feel warm, and after a few minutes the water temperature alarm, immediately read fault codes, still 2E84.
is performed using the fault diagnostic function diagnostic element to drive the electric cooling fan, the cooling fan is operated diagnostic tips 30 s, the cooling fan can be seen from low speed to high working stepless 30 s, the cooling fan is determined without failure, but can not afford to clear the fault code. Careful analysis of failure phenomena, the cooling fan failure will not cause plumbing such a big temperature difference, the problem should still be circulating a cooling fluid. Access to information, we can see that the car’s cooling system and the previous model has been very different, a lot of complexity, BMW E65 730Li sedan equipped with engine heat management system, this system consists of an electric water pump, electronic thermostat the main components of a cooling fan or the like and a variable speed, already a complete, the electric water pump operating speed, the rotational speed of the cooling fan is turned on and an electronic thermostat is controlled by a electrically driven cooling system DME by the engine control unit, electronic water pump and serial data transmission line between the fan and the electronic engine control unit, engine control unit integrated various data calculated engine operating temperature, and passed through the data line to the electronic waterElectronic fan pump and the engine is maintained at the desired temperature value.
has the following engine control unit adjusts the temperature of the engine when the node temperature: 112 ℃ mdash; mdash; economic, 105 ℃ mdash; mdash; standard, 95 ℃ mdash; mdash; Senior, 80 ℃ mdash; mdash; advanced and regulated by thermostat characteristic line. If the engine control unit detects the operating range depending on the traveling performance may be more ldquo; economical rdquo;, DME will be adjusted to a higher temperature (112 ℃), operating at a relatively low temperature range in the fuel demand of the engine. Use fault diagnostic function diagnostic actuator driven electronic water pump, the water pump does not turn found, measuring the electronic water pump on the right side of the engine compartment fuse relay box with the fuse holder in an engine test lamp, with a power supply pilot lamp may normally lit. Disconnect the fuse, the fuse holder view and did not find bad, re-plug fuse, driving the water pump again, this pump can operate normally (Vice kettle to have a small electronic pump water pipes, water pipes when the electronic pump is running to this Vice kettle pump water), it appears to be electronic pumps appear occasionally catching phenomenon, so sometimes work and sometimes do not work. But why can not find any fault diagnostic code electronic pump it? So I tried to unplug electronic fan, starting the engine, the engine system can be seen that more than one fault code 2EFE (electric fan), the original problem of diagnostic. BMW consulting special maintenance station, meaning that fault code is 2E84 ldquo; electronic water pump communication rdquo;, meaning for 2EF5 ldquo; cooling control according to the characteristic curve (electron thermostat) rdquo;, 2E81 meaning of ldquo; electronic water pump rotational speed difference rdquo;, 2E82 meaning of ldquo; electronic water pump overcurrent closed rdquo ;. Electronic water pump having a self-test function, comprising a rotational speed difference can be diagnosed, jamming (since the foreign matter or jammed due to inflexible), the mixing ratio of water coolant and error, the cooling air in the system and the use of an external 24 V starter battery, etc. malfunction.
The electric water pump
Troubleshooting: then replace the electronic pumps, tracking return confirmation troubleshooting. Note that, the car is coldCooling system by means of exhaust air required for operation of the actuator driver diagnostic, electronic pump operating to the exclusion of air.
Review Summary: As the car is equipped with a more advanced thermal management system, the cooling system fault diagnosis and maintenance of transmission has been the nature of the difference. Maintenance of such a failure must be clear basic principle of them, to be able to repair hands. Limousine must also help repair the original instrument, if the original fault diagnostic GT1 In this case, the failure of the repair, then troubleshooting should be quite easy.
(Wang Shujie)