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HOMESERVICE MANUALSHONDA2005ACCORD L4-2.4LREPAIR AND DIAGNOSISHEATING AND AIR CONDITIONINGCONTROL ASSEMBLYTESTING AND INSPECTIONAUDIO-HVAC DISPLAY MODULE ILLUMINATION TROUBLESHOOTING
2005 Honda Accord L4-2.4L
Audio-HVAC Display Module Illumination Troubleshooting
2005 Honda Accord L4-2.4LSECTION Audio-HVAC Display Module Illumination Troubleshooting
Audio-HVAC Display Module Illumination Troubleshooting
NOTE: If the display is blank when the headlights are off, the problem is not in the illumination circuit.
1. Turn the ignition switch to the ON (II) position.
2. Turn the combination light switch ON.
3. Turn the illumination control dial on the gauge control module back and forth between full dim and full bright.
Does the problem with the illumination affect only the audio-HVAC display panel?
YES - Go to step 4.
NO - Go to B-CAN Diagnosis Test Mode A.
4. Turn the illumination control dial on the gauge control module back and forth between full dim and full bright while watching the audio-HVAC display panel buttons, button LEDs, LCD displays.
5. Proceed with the diagnostic procedure for the appropriate symptom(s).
6. Remove the audio-HVAC display module and check for loose wires terminals or poor connections at audio unit connector A (20P).
Are all the wire terminals tight, and is audio unit connector A (20P) connected properly?
YES - Go to step 7.
NO - Repair the loose wire terminal, or properly connect audio unit connector A (20P) and recheck the symptom.
7. Turn the illumination control dial on the gauge control module to the full bright position.
8. Measure the voltage between the No. 19 and No. 20 terminals of audio unit connector A (20P).
Is there 1 V or less?
YES - Check connections at audio unit connector A (20P). If connections are OK substitute a known-good audio-HVAC display module and recheck the symptom. If the symptom is gone, replace the original audio-HVAC display module.
NO - Repair open in the RED wire between the MICU and the audio-HVAC display module.
9. Remove the audio-HVAC display module and check for loose wire terminals or poor connections at audio unit connector A (20P).
Are all the wire terminals tight, and is audio unit connector A (20P) connected properly?
YES - Go to step 10.
NO - Repair the loose wire terminal, or properly connect audio unit connector A (20P) and recheck the symptom.
10. With the combination light switch still ON, turn the illumination control dial on the gauge control module to the full bright position.
11. Measure the voltage between the No. 9 and No. 20 terminals of the audio unit connector A (20P).
Is there battery voltage?
YES - Check connections at the audio unit connector A (20P). If connections are OK substitute a known-good audio-HVAC display module and recheck the symptom. If the symptom is gone, replace the original audio-HVAC display module.
NO - Repair open in the RED/BLK wire between the under-hood fuse/relay box and the audio-HVAC display panel.
12. Remove the audio-HVAC display module and check for loose wire terminals or poor connections at climate control unit connector B (16P).
Are all the wire terminals tight, and is climate control unit connector B (16P) connector connected properly?
YES - Go to step 13.
NO - Repair the loose wire terminal, or properly connect climate control unit connector B (16P) and recheck the symptom.
13. Turn the illumination control dial on the gauge control module to the full bright position.
14. Measure the voltage between the No. 12 and No. 6 terminals of climate control unit connector B (16P).
Is there 1 V or less?
YES - Go to step 15.
NO - Repair open in the RED wire between the MICU and the climate control unit.
15. Measure the voltage between the No. 8 and No. 6 terminals of the climate control unit connector B (16P).
Is there battery voltage?
YES - Check connections at climate control unit connector B (16P). If connections are OK substitute a known-good audio-HVAC display module and recheck the symptom. If the symptom is gone, replace the original audio-HVAC display module.
NO - Repair open in the RED/BLK wire between the under-hood fuse/relay box and the climate control unit.
NOTE: If the display is blank when the headlights are off, the problem is not in the illumination circuit.
1. Turn the ignition switch to the ON (II) position.
2. Turn the combination light switch ON.
3. Turn the illumination control dial on the gauge control module back and forth between full dim and full bright.
Does the problem with the illumination affect only the audio-HVAC display panel?
YES - Go to step 4.
NO - Go to B-CAN Diagnosis Test Mode A.
4. Turn the illumination control dial on the gauge control module back and forth between full dim and full bright while watching the audio-HVAC display panel buttons, button LEDs, LCD displays.
5. Proceed with the diagnostic procedure for the appropriate symptom(s).
6. Remove the audio-HVAC display module and check for loose wires terminals or poor connections at audio unit connector A (20P).
Are all the wire terminals tight, and is audio unit connector A (20P) connected properly?
YES - Go to step 7.
NO - Repair the loose wire terminal, or properly connect audio unit connector A (20P) and recheck the symptom.
7. Turn the illumination control dial on the gauge control module to the full bright position.
8. Measure the voltage between the No. 19 and No. 20 terminals of audio unit connector A (20P).
Is there 1 V or less?
YES - Check connections at audio unit connector A (20P). If connections are OK substitute a known-good audio-HVAC display module and recheck the symptom. If the symptom is gone, replace the original audio-HVAC display module.
NO - Repair open in the RED wire between the MICU and the audio-HVAC display module.
9. Remove the audio-HVAC display module and check for loose wire terminals or poor connections at audio unit connector A (20P).
Are all the wire terminals tight, and is audio unit connector A (20P) connected properly?
YES - Go to step 10.
NO - Repair the loose wire terminal, or properly connect audio unit connector A (20P) and recheck the symptom.
10. With the combination light switch still ON, turn the illumination control dial on the gauge control module to the full bright position.
11. Measure the voltage between the No. 9 and No. 20 terminals of the audio unit connector A (20P).
Is there battery voltage?
YES - Check connections at the audio unit connector A (20P). If connections are OK substitute a known-good audio-HVAC display module and recheck the symptom. If the symptom is gone, replace the original audio-HVAC display module.
NO - Repair open in the RED/BLK wire between the under-hood fuse/relay box and the audio-HVAC display panel.
12. Remove the audio-HVAC display module and check for loose wire terminals or poor connections at climate control unit connector B (16P).
Are all the wire terminals tight, and is climate control unit connector B (16P) connector connected properly?
YES - Go to step 13.
NO - Repair the loose wire terminal, or properly connect climate control unit connector B (16P) and recheck the symptom.
13. Turn the illumination control dial on the gauge control module to the full bright position.
14. Measure the voltage between the No. 12 and No. 6 terminals of climate control unit connector B (16P).
Is there 1 V or less?
YES - Go to step 15.
NO - Repair open in the RED wire between the MICU and the climate control unit.
15. Measure the voltage between the No. 8 and No. 6 terminals of the climate control unit connector B (16P).
Is there battery voltage?
YES - Check connections at climate control unit connector B (16P). If connections are OK substitute a known-good audio-HVAC display module and recheck the symptom. If the symptom is gone, replace the original audio-HVAC display module.
NO - Repair open in the RED/BLK wire between the under-hood fuse/relay box and the climate control unit.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.