It could also be these reasons.

Speaking of after-treatment failures before, it is usually the failure of the diesel engine urea pump and nozzle, but the SCR box is also an important component. Its role is to serve as a place to fully mix and chemically react the urea liquid with the nitrogen oxides in the exhaust gas. Currently, the SCR box for heavy trucks integrates the SCR catalytic converter and engine exhaust muffler with one.

The overall material is stainless steel, the SCR catalyst core and the muffler pipeline are installed inside, and the lower part of the stainless steel plate on the surface is equipped with thermal insulation material. The average surface temperature during operation is 200-250 °C. The flange face interface is the inlet, and the other light pipe interface is the outlet. The catalytic converter is equipped with temperature sensor, nitrogen and oxygen sensor, etc.

Typical failure one: SCR box intake pipe and box connection cracking

Causes:

1, the exhaust pipe is too long and no flexible junction and fixed support, resulting in the SCR box air inlet cracking under excessive force.

2, SCR box itself welding production quality problems.

Treatment measures.

1, re-welding repair or replacement of SCR box, the exhaust pipeline to increase the appropriate exhaust pipe bracket to reduce the bracket transition vibration caused by cracking SCR box

Typical fault 2: Abnormal noise in the SCR box

Causes:

1. The inside of the SCR box is crystallized, and the crystals fall off and roll and hit inside.

2. The internal welding of the SCR box is cracked, and the abnormal sound is different from that of the crystal, and there is the sound of iron hitting iron.

3. The carrier falls off and breaks, and this failure mode occurs less frequently.

Treatment measures:

Open the SCR box to check, if it is a crystallization problem, remove the crystallization and clean it carefully with pure hot water until the cleaning is completed. It is recommended to replace the assembly if the welded joint is broken and the carrier falls off.

Typical fault 3: SCR box crystals block exhaust, high back pressure, high exhaust temperature, high fuel consumption, and insufficient power

Causes:

1, Nozzle failure, large injection volume, urea consumption is super high resulting in serious crystallization.

2, Bad oil and air filter lead to the discharge of impurities, impurities adsorption urea, long time accumulation caused by crystallization.

3, Poor urea.

Treatment measures

1、Check whether the urea is qualified urea, whether it is the wear and blockage caused by urea impurities to the nozzle, causing the valve body to close poorly or not close, clean or replace the nozzle, clean or replace the SCR box.

2、 Check whether the oil and air filter are qualified, fill with qualified oil and replace the air filter.

Typical fault four: SCR box is blocked by debris

Remarks: This problem will cause the vehicle to idle on the spot. After the SCR is blocked, there is basically no airflow out of the tail pipe. There is a clear difference between the airflow of the new car's idling tailpipe.

Causes:

1, Bad oil, impurities in the oil.

2, Poor air filter or maintenance is not timely resulting in too many impurities in the intake air

Typical fault five: The muffler cotton at the exhaust end of the SCR box comes out

Causes:

1. The welding quality of the rear muffler plate is defective, and the welding is not firm, which leads to the break of the welding port.

Treatment measures:

Replace the muffler plate and weld it firmly or replace the SCR assembly