A typical Electronic Control Unit(ECU) performs Open Circuit(OC), Short to Ground(STG), and Short to Battery(STB) Diagnostics on selected internal and external pins in the ECU.

For example, consider a external output pin. There is a wire connected from this pin to somewhere else. If this wire is cut, software will detect OC fault. Or if the output impedance reaches OC threshold, software will detect OC fault.

For some Automotive Advanced Drive Assist System(ADAS) ECU, one Original Equipment Manufacturer(OEM) requires supplier to implement software and hardware to detect OC, STG, and STB faults on all external Digital Outputs and PWM Outputs. They also require supplier to detect these faults on all internal Serial Peripheral Interface(SPI) busses. What might be the reason for selecting these pins for fault detection? Why not some other pins? Maybe fault detection is required on these pins to meet some safety standard?

Consider a Level 2 Autonomous Camera ECU and Radar ECU that support features such as Lane Departure Warning(LDW), Adaptive Cruise Control(ACC), Automatic Emergency Braking(AEB), etc.
What internal and external pins in Camera and Radar ECU should be detected for OC, STG, and STB faults and why?

 

I would guess safety is the biggest. One of the latest problems I have run in to is adaptive cruise / collision prevention / automatic system that quits working because of an ABS fault.

In my example the ABS / stability control ECU is a separate unit from the cruise and collision prevention system ECU. If the ABS has a fault in a sensor or valve the cruise would need to know otherwise it could command the engine (another ECU altogether), and transmission (another ECU) based on what it thinks the ABS should be doing. At the moment there is one that says the cruise won't work because of an ABS fault, but the ABS shows no faults, and as far as I know the light works normally (it did for me at least). Based on what I hear when the valves cycle after turning on the key it's either not getting power correctly or is not initializing correctly. I'd love to log the CAN and see what's gong on, but there's only so much information you can access on the internet.

Basically the safety system could ultimately be responsible for making the problem worse that what it would be with a competent driver manually operating traditional controls.

A similar scenario would be an emergency stop button on a machine in a factory, gas pump, trash compactor, or whatever. I may not have the best explanation, but the emergency stop circuit has to be a physical break in power. You can't have the emergency stop circuit connected to a PLC input and have the PLC output activate the emergency stops of the motor controllers, other PLCs, and such it controls or interacts with. You can have a relay system that is activated by the emergency stop button(s) that in turns activates the emergency stop circuits of the PLC, motor controllers. If the machine is small enough you could skip the relay altogether.

Edit...

I realized maybe that didn't show my reasoning the best, but pretty much the best way to share that sort of information between control modules is to have an physical connection for that purpose.

 

As far as what to check I would say pretty much anything that is used to make a decision or cause something to happen... which pretty much means everything.

For camera and radar I would think the fact that it is not broadcasting the correct messages at the required intervals would be enough to detect a fault. The physical fault connections would in a way be a redundant feature that will also give a bit of state information to other controllers connected to it.

 

Is this a race?
https://www.electro-tech-online.com...g-and-stb-faults-and-why.162852/#post-1416827
https://www.edaboard.com/threads/wh...g-and-stb-faults-and-why.401020/#post-1726956

 

Camera ECU Pinout

• Camera has no external input pins
• Within camera is Low Voltage Differential Signaling(LVDS) interface. It's from imager to SOC. The pins are as follows:
  • LVDS+
  • LVDS-

Radar ECU Pinout

• Radar has no external input pins