2. User Password Teaching Procedure

The user password for limp home is taught at the service station. The owner of the vehicle can select a number with four digits.

User password teaching is only accepted by a "learned" ECM. Before first teaching of user password to an ECM, the status of the password is "virgin". No limp home function is possible.

The teaching is started by ignition on, with a valid key and sending the user password by tester. After successful teaching, the status of the user password changes from "virgin" to "learned".

The learned user password can also be changed. This can be done if the user password status is "learned" and the tester sends authorization of access, either the old user password or the vehicle specific data. After correct authorization, the ECM requests the new user password. The status remains "learned" and the new user password will be valid for the next limp home mode.

If incorrect user passwords or wrong vehicle specific data have been sent to the ECM three times, the ECM will reject the request to change the password for one hour. This time cannot be reduced by disconnecting the battery or any other actions. After reconnecting the battery, the timer starts again for one hour.

THE USER PASSWORD CAN BE IN THE STATUS 

00. NOT YET CHECKED 

The status is stored in the EEPROM. In case of incorrect or no plausible data from this circuit, the ECM cannot check the status and the ECM sends 00.

01. LEARNED 

The password has been taught successfully to the ECM.

02. VIRGIN 

This is the status at the end of the ECM production line before delivery to the final customer.

04. LOCKED BY TIMER 

After a certain number of incorrect inputs, the ECM is locked for one hour and no inputs are accepted during this time.

05. TEACHING NOT ACCEPTED 

This status is set if, for example, the ECM is in neutral status.