Fault Diagnosis Strategy For Electronic Systems

Fault Diagnosis Strategy For Electronic Systems

1 The customer description of the problem is the basis for the fault diagnosis strategy.
If needed, the customer must show the problem with the car in order to avoid any misunderstanding.

2 In certain cases, the function may be correct.
a Good knowledge of the product is required to make such a decision.
b If the function is correct, it must be explained to the customer.

3 If the function is deemed to be defective, the car must be repaired.
The Saab fault diagnosis strategy is based on the condition that the technician is informed of the customer description of the problem. Therefore, note the customer complaint and any additional observations on the work order.

4 The technician obtains readouts of the diagnostic trouble codes from all systems.
A system malfunction can be caused by a fault in another system.

5 There may exist diagnostic trouble codes in the car that are secondary faults or that are generated incorrectly.
a Compare the customer complaint with the symptom description for the various diagnostic trouble codes. EPSI has a quick search path for this.
b If the symptom description for a diagnostic trouble code match the customer complaint, this diagnostic trouble code is most likely caused by the primary fault.
Repair according to instructions.

6 If there is no match with regards to trouble codes, there may be a fault diagnosis for symptoms.
a Search in EPSI during fault diagnosis in the system where the trouble exists.
b If the symptom description for the system in question matches the complaint, it is likely that the correct fault diagnosis description has been found.
Repair according to instructions.

7 If there is no match with regards to diagnostic trouble codes or symptoms, the technician must perform a fault diagnosis himself.
A final check must be performed after the repair is completed.
Good technical knowledge of the product is required to solve this type of problem.

8 The work on the car is finished.

General information about fault diagnosis in electronic systems

Control modules
When the control module is supplied with current, the processor is activated. The processor then reads instructions that are stored in the control module memory.

The control module is programmed to read off inputs and activate the outputs. If the control module programming is defective, the diagnostic trouble code "Internal control module fault" is generated.

The control module must be supplied with current for the system to function. The control module is supplied with current and the processor is activated if the control module can be contacted by the diagnostics tool.

Outputs
The purpose of the system is to control a number of functions by means of various actuators, e.g. an injector or a lamp. For the system to be capable of performing its functions, it must be possible to activate the actuators. For this reason, the actuators must be connected to the control module and have a correct power supply or ground connection.

Inputs
A condition for the control module to be able to control its actuators is that the system sensors transmit the correct information to the control module.
The function of the sensors can be checked using the diagnostics tool.