The idle speed of the truck suddenly rose.

It should be the problem of carbon deposition. I suggest watching the throttle. The van should also be maintained, otherwise the fuel consumption will go up quickly.

Conditional, you use 5053 to check the voltage fluctuation, and see if there is any instantaneous low below 1 1.5V when you engage the reverse gear;

If there is a problem with the voltage, it has little to do with the battery. The engine is working and the generator is supplying power.

Battery overcharge is due to high internal resistance, resulting in insufficient charging capacity or discharge current, which has no effect after landing.

In addition, you can turn up the air conditioner, headlights and stereo with a hot car to see if the idle speed will increase automatically. At the same time, observe the voltage change.