The Exhaust Temperature Drops Rapidly, Resulting In...
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The Exhaust Temperature Drops Rapidly, Resulting In Excessive Post-Treatment

exhaust temperature

  • Step 1: use the decoder to read the fault code. The fault code is: p01ef: the nitrogen and oxygen emission of the engine exceeds 3.5g/kw h. Current fault. In the fifth stage of China, although the fault exceeding 3.5 is reported, the torque is rarely limited and the fault exceeding 7 is not reported. It is impossible to determine whether the power shortage is caused by the fault exceeding 3.5.
  • Step 2: first check according to the troubleshooting scheme of excessive emission. First check the NOx sensor and check that its voltage and resistance are normal. Then check the urea nozzle and urea pump, and conduct the override test with the decoder. The urea is injected normally and the spray atomization is good. Use adjustable resistance to adjust the exhaust temperature to 350 ℃, conduct in-situ test, and urea is also injected normally.
The Exhaust Temperature Drops Rapidly, Resulting In Excessive Post-Treatment (2)
The Exhaust Temperature Drops Rapidly, Resulting In Excessive Post-Treatment (3)

Step 3: next, I’m confused. What causes the emission exceeding the standard? For further inspection, we decided to follow the car to check the data flow, check that the pressure build-up of urea pump is normal and the injection opening of urea nozzle is normal. However, it is found that the exhaust temperature decreases rapidly when the vehicle taxis .

The Exhaust Temperature Drops Rapidly, Resulting In Excessive Post-Treatment (4)

Step 4: the rapid drop of exhaust temperature is likely to lead to urea crystallization. Is it because urea crystallization blocks the muffler and leads to insufficient power? Therefore, the exhaust temperature sensor was removed and the muffler was tested. It was found that the pressure was slightly higher than the normal value. The muffler was not cleaned and replaced directly.

Step 5: before replacing the muffler, it is necessary to solve the problem that the exhaust temperature drops too fast. Therefore, the exhaust pipe is strictly wrapped to ensure that the exhaust temperature drops within the normal range, and then install the muffler.

Step 6: after replacement, the road test fault code is required to become a historical fault, and the fault light is off, the vehicle power is restored, and the fault is solved exceeding 3.5 is generally not calibrated as the torque limit, or it may be the torque limit after dozens of hours. And the exhaust temperature drops too fast, which is also a difficult fault point to think of. Generally, this will not be considered. If it is ignored, it is likely that this fault will occur after cleaning the exhaust pipe and replacing the muffler .

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