What is the fault with Aumark 157+18?

[LaClayton]

Excessive carbon deposits at the intake system and intake valve roots cause the air-fuel mixture to be too lean during cold starts. Additional information on carbon deposits is as follows: 1. Introduction: Carbon deposits include two concepts: One concept refers to engine carbon deposits, which are a kind of coking substance produced by unsaturated olefins and gums in fuel under high temperatures during engine operation. The second concept refers to carbon deposits in electrical discharge machining, where carbon deposits should be avoided as much as possible, especially in precision mold processing, as they can have fatal effects. 2. Formation reasons: Carbon deposits in the combustion chamber are caused by the tiny carbon particles produced after the explosion of gums and unburned hydrocarbons in gasoline, which fail to be discharged with the exhaust gas and accumulate in the combustion chamber. These black particles should be emitted into the atmosphere with the exhaust gas or accumulate on the muffler pipe.

[StAlyssa]

The fault code 157+18 on the Aumark usually indicates an issue with the after-treatment system. I've encountered many truck drivers with this problem—when the fault light comes on, the dashboard displays 157+18, and the vehicle noticeably lacks power while consuming more fuel. The key areas to inspect are the NOx sensor and the urea system, especially since the sensor connector is prone to water corrosion, and wiring damage or short circuits are common. Once, while repairing a fellow driver's truck, I found the urea pump filter completely clogged; after cleaning it, the fault code cleared on its own. Such issues shouldn't be delayed—if the urea system isn't functioning properly, not only will emissions exceed standards, but it could also damage the DPF, leading to costly repairs.

[VanMason]

157+18 on the Foton Aumark basically points to an NOx sensor failure. I remember fixing one last month where the owner reported sudden torque limitation on the highway. Using the diagnostic tool to read the data stream, we found abnormal voltage fluctuations in the NOx sensor signal. Upon disassembly, the sensor probe was severely carbon-fouled, blackened as if smoked. The fault disappeared after replacing the sensor. This type of failure is usually accompanied by abnormal urea injection, so it's advisable to also check for urea nozzle crystallization. If the vehicle is under warranty, hurry to a service station—replacing an OEM sensor out of pocket costs over 2,000 yuan.

[DiJuliana]

I'm familiar with this fault code, it's common in the Aumark series. The core issue is abnormal signal from the NOx sensor in the aftertreatment system. Don't rush to replace parts - 80% chance it's just a loose connector or worn wiring. Open the engine compartment, follow the blue wiring harness to locate the sensor connector, and wiggle it to check contact stability. Last time I helped a logistics fleet, false alarms were caused by poor connector contact. If wiring is intact, use a urea tester to check solution concentration - inferior urea can cause sensor misjudgment. Remember, if the warning light stays on after power cycling, you must take it to the workshop for inspection.

[RichardLynn]

Don't panic when encountering error code 157+18, it's usually a minor issue with the emission system. My own Aumark had this problem last year, with symptoms of white smoke from the exhaust during acceleration. Follow this three-step inspection: first check if the DEF (Diesel Exhaust Fluid) level is sufficient, then verify if the DEF tank heater is working (it tends to freeze in winter), and finally unplug the NOx sensor connector to check for green corrosion on the pins. Last time, it was pin oxidation causing poor contact, which was resolved by sanding with sandpaper. If this code appears during long-distance travel, you can temporarily disable the engine emission reduction function as an emergency measure, but immediate repair is mandatory upon reaching your destination.