Audio Module Communication Lost
Code U1164 indicates that the Audio Control Module (ACM) or tuner/receiver has detected invalid data or missing expected messages on the SCP (J1850 VPW) communication bus. This means the audio module has lost serial communication with the vehicle network, preventing functions like steering wheel controls, data display on the cluster, or entertainment system operation.
1. Commonly Affected Makes
2. Most Common Causes
- Faulty Audio Control Module (ACM) or tuner/receiver
- Open or short circuit in the SCP bus (+/-) to the ACM
- Loose, corroded, or damaged connector at the ACM or SCP bus splice
- Another module on the SCP bus pulling the line to ground or battery (bus down fault)
- Low battery voltage or voltage fluctuations corrupting communication
3. Symptoms You Will Notice
- Steering wheel audio controls not working
- No sound from audio system
- Entertainment system display blank or showing errors
- Radio or media player unresponsive
4. Step-by-Step Diagnosis
Check battery voltage and charging system; ensure stable 12-14V
Inspect SCP bus wiring and connectors at the ACM for damage, corrosion, or looseness
Test SCP bus resistance and voltage with a multimeter (should be ~2.5V on each line with ignition on)
Disconnect other modules on the SCP bus one at a time to isolate a bus-down fault
If all wiring and voltage are good, replace the ACM/tuner
5. Frequently Asked Questions
Is it safe to drive?▼
Yes, the vehicle is generally safe to drive, but you may lose audio and steering wheel controls. Have it diagnosed soon to avoid potential battery drain or further communication issues.
How much does it cost to fix?▼
Diagnosis typically costs $100-$150. If the ACM needs replacement, parts and labor can range from $300 to $800, depending on the vehicle.