OBD-II Code · Network
U0073
Control Module Communication Bus A Off
Severity
high
Left alone, this one tends to take other parts with it.
Can you drive it
Not for long
Driving on this one risks further damage. Get it to a shop rather than carrying on with it.
Indicative cost (USD)
$100–$2,000
Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
A module has gone offline from the CAN bus.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then work the likely-causes list in the order shown.
That order is what a shop checks first for this code — wiring and connections before the component they run to, because a connector costs nothing to inspect and is a common answer.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Multiple warning lights
- Limp mode
- Gauges inoperative
Likely causes
- Shorted CAN bus wiresMost common
- Failed module dragging bus down
- Water damage
Read the full diagnostic procedureU0073 means the CAN bus A controller has shut itself off, which is a self-protection mode triggered when a module detects bus errors exceeding its er…
U0073 means the CAN bus A controller has shut itself off, which is a self-protection mode triggered when a module detects bus errors exceeding its error-counter threshold (typically 255 frame errors per ISO 11898). This is a bus-level fault, not a module fault, and replacing modules first is exactly the wrong move.
Cheapest-first
- with the key off and battery disconnected, measure DLC pin 6 to pin 14: you must read 60 ohms.
- Reading 120 ohms means one terminator is missing (open wire, disconnected module, or failed internal terminator).
- Reading 40 ohms or less means an extra terminator or shorted module.
- Reading 0 ohms means CAN-H is shorted to CAN-L. Then disconnect modules one at a time (start with the most recently serviced or the most water-exposed: ABS, trailer module, aftermarket radio, aftermarket remote start) and re-measure.
- With the bus restored, key on, scope CAN-H and CAN-L: idle bus should sit at 2.5V on both legs, active bus should swing CAN-H to 3.5V and CAN-L to 1.5V in a mirrored pattern.
- Caveat: aftermarket installations (remote start, trailer brake controllers, dashcams hardwired to CAN) cause more U0073s than any single OEM defect, so always ask about recent installs before ordering parts.
Vehicle-specific patterns2008-2014 Dodge/Ram with TIPM-integrated gateway sets U0073 when the TIPM's internal CAN driver fails.
- 2008-2014Dodge/Ram with TIPM-integrated gateway sets U0073 when the TIPM's internal CAN driver fails.
- 2003-2007GM trucks with Class 2 and early GMLAN see U0073 from chafed bus wire at the body-to-frame harness behind the driver's seat.
- 2010-2015Ford F-150 sees U0073 from aftermarket trailer brake controller back-feeding into the trailer-tow CAN spur.
- 2006-2012BMW E90/E60 throws U0073-equivalent (BMW codes A0B1/A0B2) when the PT-CAN or K-CAN twisted pair gets damaged at the kick-panel splice.
Estimated repair$50 to $1400.
Look up another code
U0073 — frequently asked
What does a U0073 code mean?
A module has gone offline from the CAN bus.
What causes a U0073 code?
Common causes: Shorted CAN bus wires; Failed module dragging bus down; Water damage.
What are the symptoms of a U0073 code?
Typical symptoms: Multiple warning lights; Limp mode; Gauges inoperative.
Is it safe to drive with a U0073 code?
Not for long. Driving on this one risks further damage. Get it to a shop rather than carrying on with it. Estimated repair: $100-$2,000.
How do I diagnose a U0073 code?
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed. 1. Note every code that is set, not just this one. 2. Read the freeze frame — the conditions the fault was recorded under. 3. Confirm the fault is current rather than history. 4. Then work the likely-causes list in the order shown.
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