This is for Paul for cars without the sat nav as standard. Turn the ignition switch to ON (II). Turn the audio unit off. Push and hold the No. 1 and No. 6 buttons. While holding the buttons, push the VOL to on. Release the buttons and the self-diagnostic function begins. By pressing a pre-set button, the input will trigger the diagnostic mode that is assigned to that pre-set switch. No. 3 button. Entire LCD lighting/light-out mode: Turns on/off the entire LCD to show the presence or absence of an LCD failure. No. 4 button. Illumination level indication mode: Indicates the duty cycle for the illumination dimmer control of the gauge assembly. Gauge dimmer control values: Headlights off: OFF Headlights on: 01 (max low) through 22 (max high) AM/FM or FM button (Push and hold 5 sec.) Reception level check mode: Indicates the reception level. When entering the reception level check mode, the AM/FM button or FM button is used to change the main/sub antenna.