Limp Home By Ignition Key
The limp home can be activated also by the ignition key.
The BCM informs the driver by driven the status indicator about the limp home condition.
Then the input of user password to BCM can be done by special sequence of ignition on/off. The timing is described in the following diagram.
- Ignition On period: 0.2-5 seconds
- Ignition Off period: 0.2-3 seconds
- Pausing duration between two passwords input: 3-10 seconds
If wrong user password is recognized by BCM three times, the BCM will reject the request of limp home for one hour. Disconnecting the battery or other manipulation cannot reduce this time. After the connecting of battery to ECM the timer starts again for one hour. When a valid TP is authenticated before counter value reaches to limit, the counter is reset, but the timer counter (1 hour) is not affected.
Only if the BCM is in status " learnt" and the user password status is " learnt" and the user password is the correct one, the BCM is released and the ECM is unlocked for the time (typical 30 seconds). The engine can be started during this time. After elapsing of timer no engine start is possible. After new input of user password the timer (typical : 30 seconds) starts again.
After ignition off the BCM is blocked and the ECM is locked (typical 10 seconds) is elapsed. For next start the input of user password is requested again.