Workshop Manuals Factory service & repair Lancia
Lancia Thesis Factory Service Manual (2002-2009)22 · Fault diagnosis
22 · Diagnostics

Brake lights and third brake light not working

Make
Lancia
Model
Thesis Factory Service Manual
Year
2002–2009
Section
Lights › Brake lights and third brake light not working
Fault diagnosisBrake lights and third brake light not working

BRAKE LIGHTS AND THIRD BRAKE LIGHT NOT WORKING

The rear brake lights and the third brake light are not working;

The left and right brake lights are operated directly by the Body Computer Node using information coming from the brake lights switch.

The Body Computer Node directly controls the condition of the Brake Lights fuse and, using information coming from the rear light clusters via a dedicated serial line, the condition of the left and right Brake Lights.

Faults in the rear light clusters and the fuse are memorized by the Body Computer Node and are displayed in the Instrument Panel Node via appropriate messages in the B-CAN. The third brake light is controlled directly by the switch on the pedal assembly.

STEPOPERATIONS TO BE CARRIED OUTTEST RESULTS
1BRAKE LIGHTS FUSE CONDITION CHECK.ALL OKPROBLEMS ENCOUNTEREDACTION
Check the condition of the brake lights protective fuse.Move on to StepFuse blownReplace the fuse
2ELECTRICAL SYSTEM CHECK.ALL OKPROBLEMS ENCOUNTEREDACTION

Check the following in the dashboard junction unit:

  • the presence of the positive output to the brake lights switch
  • the presence of the positive input from the brake lights switch with the brake pedal pressed.
Move on to Step1. No positive output to the brake lights switchMove on to Step
2. No positive input from the brake lights switch

(Wiring Diagram ) E2021 BRAKE LIGHTS

Move on to Step

3ELECTRICAL SYSTEM CHECKALL OKPROBLEMS ENCOUNTEREDACTION
check the continuity/insulation between the dashboard junction unit and the brake light switch.Move on to StepWiring faulty

Repair the electrical connections

(Wiring Diagram ) E2021 BRAKE LIGHTS

4BRAKE LIGHTS SWITCH CHECK.ALL OKPROBLEMS ENCOUNTEREDACTION
Disconnect the brake lights switch and check that it is working.Move on to StepBrake lights switch faulty.

Replace the brake lights switch

See in Op. 5550D10 brake light switch - r+r

5DASHBOARD JUNCTION UNIT CHECKALL OKPROBLEMS ENCOUNTEREDACTION
Remove the dashboard junction unit, separate it from the Body Computer Node and check the internal continuityMove on to StepDashboard junction unit internal interruption

Replace the dashboard junction unit

See in Op. 5505A10 Junction UNIT - R.R.

6CHECK ON CORRECT OPERATION.ALL OKPROBLEMS ENCOUNTEREDACTION
Check that the fault is no longer present

Parts & tools for this job For 2002 Lancia Thesis

Links open Amazon search results in a new tab. As an Amazon Associate I earn from qualifying purchases.