Initial Inspection and Diagnostic Overview
Diagnosis of Battery VoltageGeneral Description
A signal below the threshold is not plausible, since the processor of the ECU is not operational if the voltage is less than or equal to 2.5V. A substitute value is therefore used.
The max. value check is only effective after a delay period from the end-of-start and only with a vehicle speed greater than zero (with a speed signal without faults).
The check of the min. value (fault in the vehicle s electrical power supply system) is only allowed after a delay time from the end-of-start, when the voltage has recovered from the starter activation, see Diagnosis of Battery Voltage.
Injection Valve
Check is performed by using Output Stage Check
Ignition Coil
Check is performed by using Output Stage Check
Diagnosis of Battery Voltage
Output Stage Check
The output stages are integrated in manufacturer specific IC's.:
The IC has a binary diagnostic line (e.g. SJ401).
If the control line of one stage has a different signal than the output line, the logic circuit inside the IC detects a malfunction. The logic circuit within the IC can separate the type of fault to a short circuit to minus, an open line, or a short circuit to plus. The check result will be sent to the ECM via diagnosis line.
Signal tables of output stage check
