Control Module Communication Bus A Off
The U0073 code means the vehicle's onboard diagnostic system has detected: Control Module Communication Bus A Off. This is a serious severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- moderate
- Estimated cost
- $100 - $700 (wiring repair most often; a failed module holding the bus down at the high end)
Network codes mean modules are not communicating. You need a scanner that reads all systems to find the problem.
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Common Symptoms
- Multiple systems offline or erratic at once
- Several modules storing communication codes together
- Possible no-start or instrument cluster blackout in severe cases
Probable Causes (Ranked by Likelihood)
- CAN bus wiring shorted - to power, ground, or the two lines to each other High
- A failed module dragging the bus down High
- Corroded or water-damaged connector on the bus Moderate
- Failed bus terminator resistance Low
Common Fixes by Vehicle
What techs usually find when diagnosing U0073 on specific vehicles — tap your vehicle for the fix and the exact part:
2003-2014 Chevrolet Silverado/GMC Sierra hard DIY
U0073 (control module communication bus A off) on GM trucks means the high-speed GMLAN bus is not terminating. The #1 cause is a short in the CAN wiring, often at a chafed harness near the fuse box or a pinched wire under the intake. Unplug modules one at a time (ECM, TCM, BCM, EBCM) and check if U0073 clears -- the module that clears it is the one shorting the bus. Replace that module or repair its wiring.
Labor: 1-3 hours2007-2014 Ford F-150/Expedition hard DIY
Ford U0073 typically indicates a shorted CAN bus wire, often at the firewall grommet or a pinched wire at a module connector. Disconnect the battery, then unplug modules one at a time and recheck -- isolating which module/circuit is pulling the bus down. Ford FORScan is extremely helpful here for watching module communication status live.
Labor: 1-3 hours2005-2015 Dodge Ram 1500/2500 hard DIY
Ram U0073 is often caused by water intrusion into the TIPM (Totally Integrated Power Module) in the underhood fuse box. Dodge TIPMs are notorious for internal corrosion. Remove the cover, inspect for green corrosion on circuit traces, and replace or rebuild the TIPM if corroded. A dead TIPM can take down the entire CAN network and trigger U0073 plus a dozen other U-codes.
Labor: 2-4 hoursFrequently Asked Questions
What does U0073 mean?
U0073 is a vehicle network (CAN bus) fault: Control Module Communication Bus A Off. The bus itself - wiring, terminators, or a module pulling it down - is disturbed, which can take many systems offline at once.
Can I keep driving with U0073?
Usually yes for a short period. The affected function may be degraded, and intermittent wiring faults tend to worsen - diagnose soon.
Should I replace the module for U0073?
Not first. Most communication codes are power, ground, fuse, or wiring problems. Replace the module only after those test good - modules are expensive and often require programming.
Mechanics Guide Step-by-step diagnosis
Step-by-Step Diagnostic Procedure
-
Measure resistance across CAN High and Low with the battery disconnected: about 60 ohms is normal, about 120 suggests a lost terminator, near 0 a short.
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Check the bus voltages: CAN High idles near 2.5-3.5V, CAN Low 1.5-2.5V; both pinned at 0 or 12V means a short.
-
Unplug modules one at a time to find one holding the bus down.
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Inspect bus wiring at high-wear points - door jambs, under carpets, near exhaust heat.
Sources 1
This page is built from documented references. Verify against your own service info before repair work.
- SAE J2012Diagnostic Trouble Code Definitions (defines the generic OBD-II code ranges)
U0073 on Diesel, EV & Equipment
The same code ID appears across other engines and platforms. The diagnostic flow varies by manufacturer — these are the platform-specific breakdowns:
Commonly Affected Vehicles
- All OBD-II vehicles - network (U) codes are standardized across makes
See All Codes & Fixes for Your Vehicle
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