U0073: U0073: Control Module Communication Bus A Off
Standard SAE J1979 OBD-II diagnostic trouble code definitions, freeze-frame sensor telemetry, electrical multimeter benchmarks, and step-by-step DIY repair flowcharts.
1. Symptoms & Warning Signs
When fault code U0073 is triggered by the Engine Control Module (ECM), drivers frequently experience the following symptoms:
2. Most Likely Causes
Root cause statistical probability compiled from NHTSA ODI complaint telemetry, ASE Master Technician field records, and OEM Factory Service Manual diagnostic trees for U0073:
3. Step-by-Step DIY Repair Instructions
Remove any aftermarket insurance dongles, GPS trackers, or scan tools plugged into the DLC port.
Inspect braided ground straps on engine and transmission. Clean all contact surfaces to bare metal.
Scan all modules on vehicle. Note which modules are online and which are offline to pinpoint the break in the network daisy-chain.
Verify 60 ohms across Pins 6 and 14 with battery disconnected.
Clear DTCs from all modules and road test to verify error-free network transmission.
Equipment for Diagnosing Universal Automotive (U0073)
Universal Automotive OEM Replacement Sensor
Direct-fit replacement assembly engineered to OEM tolerances for Universal Automotive.
AstroAI Auto-Ranging Digital Multimeter
Essential for testing 0.1V–5.0V sensor reference signals, ground continuity (<0.20Ω), and harness resistance.
BlueDriver Bluetooth Pro OBDII Scan Tool
Reads and clears enhanced codes (ABS, Airbag, Transmission, Engine) & live freeze-frame telemetry on phone.
Fix U0073 on 25 Specific Automakers
Manufacturer-specific wiring harnesses, sensor pinouts, and Technical Service Bulletins for U0073:
4. U0073 Frequently Asked Questions
What causes 'Bus Off' condition?
When a module detects too many transmit error frames (typically over 255 consecutive transmit errors), it automatically disconnects itself from the bus to prevent taking down the whole network.