U0044 — Vehicle Communication Bus B (-) High

What does OBD2 code U0044 mean?

U0044 — Vehicle Communication Bus B (-) High. A fault in the vehicle network (CAN bus) communication. Short, gentle driving to a shop is usually possible. Typical causes: a faulty module pulling the bus down, corroded connectors, especially in wet areas, aftermarket equipment interfering with the bus.

How do I diagnose U0044 myself?

Start with a scan: confirm U0044, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the vehicle network (CAN bus) communication, and verify the suspect component against live data before buying parts.

Will U0044 clear itself?

Sometimes U0044 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.

What are the symptoms of U0044?

Drivers most often notice: random, hard-to-reproduce electrical glitches, multiple warning lights on at once, modules intermittently not communicating with the scanner, intermittent loss of functions (gauges, windows, steering assist).

How much does it cost to fix U0044?

Repair CAN wiring or connectors — $100–$400; Replace the faulty control module — $300–$1,500; Remove interfering aftermarket device — $0–$150. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

What does U0044 mean?

U0044 (Vehicle Communication Bus B (-) High) is stored when self-diagnostics detect abnormal readings or behaviour of the vehicle network (CAN bus) communication. It belongs to the vehicle network category.

To set U0044, the control module compares live readings of the vehicle network (CAN bus) communication against calibrated limits, usually over several drive cycles. Alongside the code it stores a freeze frame — a snapshot of rpm, load, coolant temperature and vehicle speed at the moment of failure. Reading that snapshot first saves diagnostic time.

What causes U0044?

• aftermarket equipment interfering with the bus
• water ingress in harness junctions
• corroded connectors, especially in wet areas
• damaged CAN bus wiring or short to power/ground

Common symptoms of U0044

• random, hard-to-reproduce electrical glitches
• multiple warning lights on at once
• modules intermittently not communicating with the scanner
• intermittent loss of functions (gauges, windows, steering assist)
• no-start or intermittent starting in some cases

How to diagnose U0044

1. Connect an OBD2 scanner, confirm U0044 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
2. Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many U0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
3. Visually inspect the wiring harness and connectors related to the vehicle network (CAN bus) communication for damage, corrosion, chafing or poor contact.
4. Measure resistance between CAN-High and CAN-Low at the OBD port with power off — about 60 Ω is healthy.
5. Scan all modules: the one that does not respond is either the culprit or downstream of the break.
6. Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm U0044 does not return.

How to fix U0044

Start with the cheapest and most common causes before replacing expensive parts:

• Repair CAN wiring or connectors — $100–$400
• Replace the faulty control module — $300–$1,500
• Remove interfering aftermarket device — $0–$150

How much does it cost to fix U0044?

Repair cost depends on which component actually failed. Typical scenarios for U0044 (parts and labor, USD, independent shop rates):

• Repair CAN wiring or connectors: $100–$400
• Replace the faulty control module: $300–$1,500
• Remove interfering aftermarket device: $0–$150

Overall, fixing U0044 usually costs between $0 and $1,500. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Can you drive with U0044?

Depends on what is affected. A single dead convenience module is fine to drive with; loss of communication with engine, braking or steering modules is not. If multiple critical systems drop out, do not drive.

Related OBD2 codes

• U0001: High Speed CAN Communication Bus
• U0002: High Speed CAN Communication Bus Performance
• U0003: High Speed CAN Communication Bus (+) Open
• U0004: High Speed CAN Communication Bus (+) Low
• U0005: High Speed CAN Communication Bus (+) High
• U0006: High Speed CAN Communication Bus (-) Open