OBD-II Diagnostic Trouble Code
U007A — Control Module Communication Bus H Off
U007A indicates the reporting module went bus-off on communication bus H, one of the additional networks on vehicles with many segmented buses. Too many CAN errors caused the module to stop transmitting on that bus. Bus H usage is OEM specific.
Severity 3/5
Truck-relevant
Service this week
Severity
Service this week
Control Module Communication Bus H Off
Code
U007A
Category
Network
Subsystem
Network
Truck-relevant
Yes
What this means for truckers
Service within a few days on a Cummins X15, Detroit DD15, PACCAR MX-13. Performance is likely degraded. Continuing to drive without service risks additional component damage.
Before you replace parts — try this first
U007A on the Network system is most often bus h wiring short or open — not a dead part. On commercial diesels especially, work these in order before spending money on parts:
- Confirm the symptoms. Match what your truck is doing to the Symptoms section below. If the code is set but the symptoms are not there, clear the code and re-test after a drive cycle — it may not return.
- Clean and dry the sensor connector. Water, road salt, or oil seeping into a connector is the #1 fake sensor failure. Disconnect, look for green corrosion or moisture, spray with electrical contact cleaner, dry, reseat. Many faults clear here for $0.
- Inspect the wiring harness. Trace the wire from the sensor toward the ECM — look for chafing against the engine block, melted insulation near the turbo or exhaust, or pinch points where a clamp has rubbed through.
- Test the sensor before swapping it. Most Common Causes (below) list the expected voltage or resistance range — a $20 multimeter saves a $300 sensor swap that does not fix the problem.
- Only then, replace the part. Use the OEM or a tier-1 aftermarket. Cheap sensors throw the same code in two weeks.
Symptoms
Functions on bus H stop or act erratically, with warning lamps and related U-codes. Driveability impact depends on which modules bus H connects.
Common causes
- CommonBus H wiring short or open ($150–$800)
- CommonCorroded or loose connectors ($100–$500)
- OccasionalFaulty module on bus H ($500–$2000)
- RareGateway module fault ($600–$1800)
How to fix
Use OEM information to identify bus H and its modules
When to use: Before testing
Test bus resistance and voltages and repair wiring
When to use: When values are out of range
Isolate modules one by one
When to use: When wiring is good but the fault returns
Affects most
No specific vehicle pattern found in our complaint database. This code can appear on any vehicle that supports OBD-II diagnostics.
Related
- → Browse all DTC trouble codes
- → Decode a VIN to check codes for your truck
- → Owner-operator maintenance guides
- → U0001 — High Speed CAN Communication Bus
- → U0002 — High Speed CAN Communication Bus Performance
- → U0010 — Medium Speed CAN Communication Bus
- → U0019 — Medium Speed CAN Communication Bus B
- → U0073 — Control Module Communication Bus Off
Frequently Asked Questions
Can I drive with code U007A?
U007A is severity 3 — plan service within a few days. Performance is likely degraded already (you may feel reduced power, harsher shifts, or slightly worse fuel economy). Continuing to drive risks additional damage to adjacent components.
How much does it cost to fix U007A on a commercial truck?
Total repair cost ranges $100–$2000 depending on the root cause. The cheapest fix is usually the first one listed below — Bus H wiring short or open — which is also the most common. On commercial trucks the cost is usually higher than passenger vehicles due to part availability and shop labor rates ($120–185/hour at most truck shops, vs $90–130 at general auto shops). DIY-capable fixes (sensors, hoses, filters) are at the low end; major component replacements (turbo actuator, high-pressure fuel pump, transmission solenoid pack) are at the high end. Always diagnose with a scan tool BEFORE replacing parts — guessing wrong on a $1,500 turbo actuator when the actual issue was a $30 boost hose is a common expensive mistake.
Will U007A fail a DOT inspection?
U007A is generally not a direct DOT inspection fail item by itself. Inspectors focus on safety-critical systems (brakes, steering, tires, lights, hours-of-service). However, the check engine light alone can trigger additional inspection scrutiny. Best practice: fix the code and clear it before a planned inspection.
What's the difference between U007A and related codes?
U007A is closely related to: U0001 (High Speed CAN Communication Bus), U0002 (High Speed CAN Communication Bus Performance), U0010 (Medium Speed CAN Communication Bus), U0019 (Medium Speed CAN Communication Bus B). These codes share the same subsystem (network) and often appear together. If you see this code, scan for the full code list — fixing the root cause usually clears multiple companion codes at once. If only U007A is set without the companions, the issue is more isolated.
How do I prevent U007A from coming back after a repair?
For U007A (Control Module Communication Bus H Off), prevention centers on the network system. Pay attention to ground connections at every PM — bad grounds are 70% of communication codes. Inspect harness routing for chafe points. Don't disconnect modules with the key on.