OBD-II Code
U0074
Severity
Not yet reviewed
Nobody on our side has assessed this code yet, so we are not going to guess at how serious it is.
Can you drive it
We cannot say
Treat it as unknown until a shop reads it with live data. If the check-engine light is FLASHING, stop driving as soon as it is safe to — that means an active misfire, whatever the code.
Indicative cost (USD)
$0–$900
From this code's diagnostic notes. Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
$0 (reflash) to $900 (BCM replacement plus theft-deferent recoding).
U0074 means the Control Module Communication Bus 'B' is reporting bus-off — the secondary CAN or LIN bus has dropped offline entirely, which on most modern platforms means low-speed body/comfort bus traffic between BCM, instrument cluster, HVAC, and infotainment has stopped.
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 follow the diagnostic notes further down this page, in the order they are written.
They are written in the order a shop works this code, cheapest checks first. Where they name a component, inspect its wiring and connector before replacing it.
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
- Check engine light
Read the full diagnostic procedureU0074 means the Control Module Communication Bus 'B' is reporting bus-off — the secondary CAN or LIN bus has dropped offline entirely, which on most…
U0074 means the Control Module Communication Bus 'B' is reporting bus-off — the secondary CAN or LIN bus has dropped offline entirely, which on most modern platforms means low-speed body/comfort bus traffic between BCM, instrument cluster, HVAC, and infotainment has stopped.
The diagnostic ladder is similar to a high-speed bus fault but on a different pinout
- pull the FSM wiring diagram first because Bus B pins vary by manufacturer (often pin 3 and pin 11 on the OBD-II connector for GM SW-CAN, or dedicated module-to-module wiring on Chrysler PCI bus and Ford MS-CAN).
- With key-on, back-probe Bus B at a known module — a healthy mid-speed CAN sits around 2.5V at rest with active pulses to 3.5V/1.5V; a single-wire CAN (GMLAN) idles near 0V and pulses to ~4V dominant. 0V or 12V on the bus wire = shorted to ground or B+. Key-off battery-disconnected resistance across the bus should read 60 ohms on dual-wire CAN; single-wire buses typically read much higher because they use a different termination scheme — check the FSM spec.
- Common-mistake caveat: U0074 frequently sets alongside U0073 and U0100 when the real failure is upstream gateway-module software, not a wiring fault — reflash the gateway/BCM with the latest calibration through the OEM scan tool before pulling harness; a $0-$150 dealer reflash beats a $600 BCM swap.
Vehicle-specific patterns2008-2014 Chrysler 300/Charger/Challenger and 2011-2014 RAM 1500 throw U0074 from TIPM internal CAN bridge failure — same TIPM defect that drives U00…
- 2008-2014Chrysler 300/Charger/Challenger and 2011-2014 RAM 1500 throw U0074 from TIPM internal CAN bridge failure — same TIPM defect that drives U0002, but Bus B traffic dies first because the TIPM brokers low-speed BCM/cluster comms.
- 2006-2012Mercedes-Benz W164 ML-class and W221 S-class commonly throw U0074 from rear SAM water intrusion in the cargo area floor, killing the rear interior CAN segment.
- 2003-2010Ford SuperDuty 6.0L/6.4L Powerstroke throws U0074 alongside U0002 when the under-hood harness near the FICM chafes, because both the HS-CAN and MS-CAN run in the same loom.
- 2014-2018GM K2XX trucks (Silverado, Sierra) throw U0074 from BCM connector corrosion at the kick panel after windshield leaks.
Estimated repair$0 (reflash) to $900 (BCM replacement plus theft-deferent recoding).
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