Does On Board Diagnostics or OBD is applicable to Engine ECU only or it is applicable to other ECU's as well like Body Control Module?

 

Other ECUs, e.g. the TCU, are covered by the OBD standard.

 

Hello,

The wiki already tells you quite a bit about the OBD:
https://en.wikipedia.org/wiki/On-board_diagnostics

Bertus

 

Does On Board Diagnostics or OBD is applicable to Engine ECU only or it is applicable to other ECU's as well like Body Control Module?

not all scan tools can both diagnose ECU et BCM same time ,
using OBD2 connector, a Knockoff Tech2 can do both, or Bluedriver Bluetooth device works great with iPhone

 

I have studied some of the online pages. One doubt is if there is a fault code for short to ground because of any component getting short to ground will there not be huge current flowing through the circuit and damaging the hardware board? Does the system only tell you that short to ground happened or it will also protect the board? Will the complete system come to a halt or only that section of the board is isolated and remaining functionality will continue? Please advise.

 

Because of the automotive environment, most components are usually reasonably well protected against wiring issues.

The effect of a short to ground depends on which circuit the short is in.
Hopefully the component will detect the over current and shut down, or go into a limp/default state.
Other times a fuse will blow before damage occurs.
Shorts can also cause major damage, eg blown circuit board tracks, destroyed electronic components etc.

An ECU that detects a short, or other wiring issues, will usually illuminate a fault light on the dash and log an error code in its memory.
If the fault is intermittent the light may go off, but the code will be retained in memory.
The code can then be viewed with diagnostic equipment at a later date.

 

Most ECUs are protected from shorts by pull-up or pull-down resistors built into the ECU. Often times when a short occurs, there is a resistor inside which creates a voltage divider with the sensor. Shorts to ground will pull the voltage low but there is still a load in the circuit internally. There are some circuits which can still damage the ECU, such as the fuel injectors. They will usually take out the injector drivers internally.

 

I have this one another clarification. You keep logging the DTCs of several components and also several related information. I assume that all these data is written in Non volatile memory preferably in EEPROM. My doubt is that the memory after probably some days(months not sure) will get filled or unusable because of limited write cycles. Am I correct in understanding. How to overcome this situation?

 

Overcome using wear levelling techniques.

 

There seem to be several ways that manufacturers overcome the possible problem of running out of memory for retaining DTC's;
1 - deletes DTC after a certain number of warm-up cycles if it doesn't reoccur,
2 - only retains a limited number of DTC's. If a new one occurs after reaching the limit, the oldest is deleted,
3 - minimal information stored, so memory can hold many DTC's,
4 - warning light on dash to advise driver to get vehicle checked,
5 - vehicle goes into a limp mode, so driver has to get it repaired to get full functionality back.