U0073 — Control Module Communication Bus A Off

Will U0073 clear itself?

Sometimes U0073 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.

Is it safe to drive with U0073?

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.

What is the most common cause of U0073?

The most common causes are: aftermarket equipment interfering with the bus, damaged CAN bus wiring or short to power/ground, water ingress in harness junctions.

What does OBD2 code U0073 mean?

OBD2 code U0073 flags a problem with the vehicle network (CAN bus) communication (control module communication bus a off). Short, gentle driving to a shop is usually possible. Common culprits: aftermarket equipment interfering with the bus, damaged CAN bus wiring or short to power/ground, water ingress in harness junctions.

How do I diagnose U0073 myself?

Start with a scan: confirm U0073, 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.

When your scanner pulls a U0073 code, it means the vehicle's onboard network has gone quiet. Specifically, the control module has detected that the CAN (Controller Area Network) bus — the communication backbone that lets different ECUs talk to each other — has stopped operating within its expected parameters. Technicians classify U0073 under the "U" codes, which cover network and data link faults rather than problems with a specific engine or emissions system.

The affected module doesn't just check once and give up. It watches the bus continuously while you drive. When the signal falls outside the acceptable range for enough consecutive drive cycles, the module logs U0073, saves a freeze frame snapshot of engine conditions at that exact moment, and turns on the check engine light (or network warning light, depending on your make). That freeze frame data — recording rpm, engine load, coolant temperature, and vehicle speed — is your most valuable clue because it tells you exactly what the vehicle was doing when the network dropped out.

Symptoms of U0073

• Gauges, power windows, or electric steering assist cutting out intermittently
• Multiple warning lights appearing on the dash simultaneously
• Electrical quirks that come and go without a clear pattern
• Scanner unable to communicate with one or more modules during a scan
• Engine cranking but not starting, or starting only on certain attempts

Common Causes

• Chafed, broken, or shorted CAN bus wiring (often to power or ground)
• A failing control module that drags the bus voltage down
• Water getting into harness connectors, especially in vehicles exposed to rain or flooding
• Corroded or loose network connectors, frequently seen in areas prone to moisture
• Weak grounds or battery voltage low enough to destabilize network communication

How to Diagnose U0073

1. Plug in your OBD2 scanner, confirm U0073 is stored, and record the freeze frame data. This snapshot shows engine conditions at the moment the fault appeared — use it as your reference point for the test drive later.
2. Look for related codes (U0100, U0121, etc.) and check for TSBs specific to your make and model. Many manufacturers have published updates or known fixes for recurring network faults. Search by VIN on the manufacturer website or NHTSA.
3. Inspect the CAN bus harness and connectors visually. Look for wire damage, melted insulation, corrosion buildup, or connectors that aren't fully seated.
4. With the vehicle powered down, measure resistance between CAN-High and CAN-Low at the OBD port. A healthy bus typically reads around 60 ohms across the terminating resistors.
5. Run a full module scan. Whichever module fails to respond is either the source of the problem or downstream from a break in the network.
6. Clear the code, then drive the vehicle through the conditions captured in the freeze frame data. If U0073 returns, you've confirmed an active fault rather than a one-time glitch.

Repair Options

• Reprogram or reset: Some cases resolve with a software update or module relearn — minimal cost if no parts needed
• Repair CAN bus wiring or connectors: $100–$400
• Replace the defective control module: $300–$1,500
• Remove an aftermarket device causing bus interference: $0–$150

Total Cost to Fix U0073

Parts and labor at independent shop rates in the United States typically run $0 if removing an aftermarket interferer resolves it, up to $1,500 if you need a full module replacement. Wiring harness repairs fall in the middle range. The key is getting a solid diagnosis before purchasing expensive components — a module is rarely the first thing to blame when a network goes silent.

Can You Drive with U0073?

Use your judgment based on which systems are affected. If only a comfort feature like the radio or power mirrors has dropped out, you can continue driving cautiously. However, if critical modules — engine control, anti-lock brakes, or power steering — are failing to communicate, the vehicle could lose throttle response, braking assistance, or steering feel without warning. Do not drive if multiple safety-related systems are offline. Have the vehicle towed to a shop for diagnosis if you are unsure.