ECU Failures

Failures Detected By Internal Time-Out
Certain hardware faults cause the ECU to be switched off by internal time-out. Any hardware fault will cause warning lamp to light continuously, and since main power is cut off, the ECU is no longer capable of storing/outputting failure codes.

Short Circuit At Diagnosis Trigger Input
If the diagnosis trigger input is shorted to ground, the ECU will go into diagnosis output mode when ignition is switched on and a failure is stored in continuous memory.
As vehicle accelerates and reaches 5 mph, short to ground on diagnosis trigger unit still exists, ECU is switched off and warning lamp lights continuously.

Warning Lamp Path Faults
Short circuiting warning lamp wire to ground will activate warning lamp, but will not affect anti-lock braking facility. ECU cannot recognize this short circuit.

Defective Warning Lamp Driver
If there is a defect in warning lamp driver inside the ECU, either warning lamp will remain continuously ON or will stay continuously ON depending on internal failure cause.

Miscellaneous Warning Lamp Displays/Conditions
In case of intermittent/defective contacts or leads in warning lamp driving path, warning lamp may flicker ON/OFF for undefined periods.
If warning lamp is blown or otherwise damaged, no information about status of ECU is possible.