Level of wear on brake rotors before replacement recommended?

When the brake booster light and brake light come on after replacing the batteries in a 2017 Isuzu NPR Diesel, it could indicate a problem with the brake system or a malfunctioning brake booster.
Here are some steps you can take to troubleshoot the issue:

1. Check the brake fluid level: Low brake fluid level can cause the brake booster light and brake light to come on. Open the hood and check the brake fluid level in the reservoir. If the level is low, top it up with the recommended brake fluid and check if the lights go off.
2. Check the brake system: Inspect the brake lines, brake pads, and brake rotors for any damage or wear. If the brake pads are worn out, replace them immediately.
3. Check the brake booster: The brake booster is responsible for increasing the force applied to the brake pedal. Check the brake booster for any damage or wear. If the brake booster is malfunctioning, it will need to be replaced.
4. Reset the brake booster light: If the brake booster light and brake light stay on even after checking the brake fluid level and inspecting the brake system, it may be necessary to reset the brake booster light. To reset the brake booster light, turn the ignition switch to the "on" position without starting the engine. Pump the brake pedal 3 times, then turn the ignition switch off. Start the engine and check if the lights go off.

If none of these steps work, it is recommended to take the vehicle to a certified mechanic or the nearest Isuzu dealership for a professional diagnosis and repair.

Check the brake fluid level. If low, you can top it off from a sealed / tightly covered can of brake fluid only. The low level of fluid also indicates that the pads are wearing and should be inspected to determine if they should be replaced soon. A squealing or scraping sound while driving or braking indicates that one or more sets of pads have worn too low and have begun scraping (and damaging) rotors. Needing to replace rotors can easily double (or more) the cost of a brake job.

heck thebrake fluid level before you go any further ,

The brake rotors are warped. This is a common occurrence. It can be caused by numerous things; excessive rotor wear (too thin), uneven brake pad wear, sticky brake calipers, riding the brake pedal causing excessive heat buildup in the rotors, and over-torque of lug nuts are just a few causes. Having the rotors checked and re-machined may help, but normally they require replacement. If you replace rotors, it is advisable to replace the brake pads at the same time to avoid a poor wear pattern.

Check Engine Light Due to Gas Cap IssueA Loose or worn gas cap may cause Check Engine Light to illuminate
Front Brake Rotor Wear Can Cause PulsationsFront brake rotors can wear causing a pulsation felt in the brake pedal. Our technicians often recommend replacement of the front rotors and brake pads as the best option to correct this condition.
Poor Ride/Handling Due to Worn Suspension StrutsThe front struts may show signs of wear, or be excessively bouncy ride at freeway speeds. This may begin to occur at around 75,000 miles
High Pressure Power Steering Hose Can Leak FluidThe high pressure power steering hose will commonly leak fluid and should be replaced if this is the case.
Corrosion of the Fuel Tank Harness Due to Water LeakCorrosion at the fuel tank to body harness may cause the Check Engine Light to illuminate or a crank no start condition. This corrosion issue is most commonly caused by a water leak inside the vehicle. Any damaged wiring or connectors will require replacement.

these are the problems faced by this cars

There are a number of reasons it could be on. Including a bad controller for the ABS, or the sensor not giving the ABS controller a signal.

go with standard pads.they wear a little faster than ceramics.but they dont wear down brake rotors.ceramics pads are hard and they cause brakes to squeak.also your car is under warranty with lexus dealership.i would use what they said. because you have future brake problem. they will void out warranty for not using their brakes.

BMW rotors are not known for lasting very much more than 30-45k miles. When the brakes are inspected, they measure the pads using a special tool threw the outer brake pad. Min spec is 3mm. When the pads are replaced, they measure the thickness of the rotors. The rotor spec is stamped on the rotor. if they are under that spec, they recommend replacing them as well. Next time you bring it in for service, just ask them to measure the rotor thinkness, (its not a huge task, all they have to do is take the wheels off). But more often than not, the rotors wear just as fast as the pads.

Haynes or Chilton manual will help out. If the inner and outer brake pads are wearing evenly, (one or more isn't worn much more than the others) and you've gone a lot of miles since the last brake job, you can probably get by with new brake pads, and having the brake rotors 'cut' (or also called 'turn' the rotors). This is a process done at a major parts store that basically grinds the front and back of the rotor to remove imperfections, grooves, etc. so the rotor is perfectly smooth. Skipping this can result in pulsating brakes (you feel the pulsating in the brake pedal). The 'shop' that resurfaces the rotor will measure it to make sure it's thick enough to grind down some more. Once it wears down to a certain point, the rotor is thrown out for safety. Depending on the make and model, it is sometimes cheaper to buy a new rotor. I have a GM car, the rotors cost $12 each, Having them 'cut' (the old ones) costs $15 at a local parts store. If brakes are not wearing out at the same time, your brake caliper(s) may need to be replaced. (Brake cylinders, if you have drum brakes). ALWAYS bleed the brake system when you do a brake job, even if you don't open any brake lines. Old fluid absorbs moisture (whenever the cap is opened to check or add fluid) and gets contaminated over time. It'll ruin your calipers and brake cylinders, which in turn will ruin your brake shoes, pads, and rotors, drums. Start at the wheel farthest away from the master cylinder, working to the one closest last. Bleed enough fluid out so that you have replaced all the old. Countrycurt0