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.
Can you duplicate the problem?
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 audio unit connector A (20P) for loose or a poor connection
Reconnect audio unit connector A (20P) and recheck the symptom; does the problem still appear?
YES - Go to step 6.
NO - Operation is normal
6. Measure the voltage between audio unit connector A (20P) No. 9 and No. 19 terminals. Operate the dash brightness controller buttons to see if the voltage changes.
Does the voltage change?
YES - Substitute a known-good audio unit, and recheck. If the symptom/indication goes away, replace the original audio unit.
NO - Repair open in the wire between the under-dash fuse/relay box and the gauge control module.