Display Does Not Dim or Brighten With Dimmer
Display does not dim or brighten with dimmer1. Turn the ignition switch ON (II).
2. Turn the combination light switch ON and OFF to see if the symptom can be duplicated.
Is it duplicated?
YES - Go to step 3.
NO - Operation is normal.
3. Turn the combination light switch OFF.
4. Operate the illumination control dial.
Is it normal?
YES - Operation is normal.
NO - Go to step 5.
5. Disconnect and check the audio unit connector A (17P) for a loose or a poor connection.
Reconnect the audio unit connector A (17P) and recheck the symptom; does it still appear?
YES - Go to step 6.
NO - Operation is normal.
6. Measure the voltage between audio unit connector A(17P) No. 1 and No. 10 terminals. Turn the instrument panel brightness control knob (at the gauge control module) to see if the voltage changes.
Dose the voltage change from 2.5 V in the fully dim position to battery voltage in the full bright position?
YES - Substitute a known-good audio unit, and recheck. If the symptom/indication goes away, replace the original audio unit.
NO - Go to step 7.
7. Check for continuity between the audio unit connector A (17P) No. 1 terminal and gauge control module connector A (20P) No. 15 terminal.
Is there continuity?
YES - Go to gauge control module input test Component Tests and General Diagnostics,and test circuit A15 and A9.
NO - Repair open in the wire between the gauge control module and the audio unit.