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Code: U0073 - The Control Module Communication Bus "A" (a main data line connecting car computers) is not working, so different vehicle systems can’t share information.

Let me break down what code U0073 actually means for your vehicle. This code pops up when your car’s computers-like the engine, transmission, and ABS modules-aren’t talking to each other the way they should. They all communicate over a special network called the CAN bus (Controller Area Network), which is basically a bundle of wires running through your car, carrying important information back and forth. When U0073 shows up, it’s telling us that the main communication line, known as ‘Bus A,’ is either completely down or having serious trouble. This can affect a whole range of systems, since modern cars can have dozens of these modules all relying on that network to work together. If that network goes down, it’s like cutting the nerves in your body-lots of things can stop working right away.

Causes of obd2 code U0073

From what I’ve seen in the shop and based on official repair info, the most common reasons for a U0073 code are:

A weak or failing battery-low voltage can really mess with the network.
Damaged wiring or loose connectors in the CAN bus harness-sometimes it’s as simple as a chafed wire or a corroded plug.
One of the control modules itself is acting up or has failed.
Water intrusion-leaks can get into connectors or modules and cause all sorts of havoc.
Poor ground connections-if a ground is loose or corroded, communication can drop out.
Occasionally, a software update or a known issue covered in a Technical Service Bulletin (TSB) from the manufacturer.

Most often the issue is with wiring or a battery that’s on its last legs, but I’ve seen all of these pop up over the years. This error can also occur on car brands such as Chevrolet, Toyota, GMC, and Chevy Silverado.

Symptoms of obd code U0073

When this code is active, you’ll usually notice some pretty obvious problems. Here’s what drivers typically report:

The check engine light comes on and stays on.
You might feel a loss of engine power-like the car just isn’t responding the way it should.
Fuel economy can drop, sometimes noticeably.
Sometimes the car won’t start at all, or you’ll get a ‘no crank’ situation.
Warning messages might pop up on your dash, like ‘Service Vehicle Soon’ or similar.
Transmission might not shift properly, or you could lose features like traction control or ABS.

Honestly, when the network goes down, all sorts of strange things can happen. It’s not always the same from one car to another, and this may include occurrences like u0073 00 chevy silverado, dtc u0073 toyota, or gmc u0073.

Diagnosis of U0073 code

Here’s how I usually approach a U0073 code, step by step:

First, I always check the battery. Make sure it’s fully charged and the terminals are clean and tight. A weak battery can cause all kinds of weird electrical issues.
Next, I do a visual inspection of the wiring harnesses, especially around the CAN bus connectors. Look for any obvious damage-broken wires, loose plugs, or signs of water getting in. Don’t forget to check under carpets and behind kick panels, since leaks can hide there.
Then, I scan for any other trouble codes. Sometimes U0073 is just a symptom of another problem, so it’s important to see what else is stored in the system.
If everything looks good so far, I’ll check for any Technical Service Bulletins (TSBs) related to your vehicle. Sometimes there’s a known issue with a particular model or year that can save a lot of time.
After that, I use a scan tool to see which modules are online and which ones aren’t responding. This helps narrow down if it’s a single module causing the problem or if the whole network is down.
If I suspect a wiring issue, I’ll do a continuity test on the CAN bus wires to make sure there’s no break or short.
Finally, if all else fails, I’ll start unplugging modules one at a time to see if one is ‘taking down’ the network. Sometimes a single bad module can cause the whole system to go offline.

It’s best to have someone assist you, especially when checking under the dash or in tight spots. And always disconnect the battery before unplugging any modules to avoid accidental damage. This is especially true when dealing with dtc u0073 chevrolet.

Common Mistakes with U0073 engine code

I’ve seen a few common slip-ups when folks try to tackle this code:

Jumping straight to replacing expensive modules without checking the basics like battery voltage or wiring.
Overlooking simple things like a blown fuse or a loose ground connection.
Ignoring water leaks-moisture can be a silent killer for these systems.
Not checking for TSBs-sometimes the answer is right there from the manufacturer.
Assuming it’s a single module every time, when it could be a wiring issue affecting multiple systems.

Don’t skip the simple checks. It’s easy to get tunnel vision with a code like this, but the basics are where most problems are found. In some cases, issues related to u0073 can be easily overlooked.

Seriousness of U0073 trouble code

This is one of those codes you really don’t want to ignore. When your car’s computers can’t communicate, you could lose critical functions like engine control, transmission shifting, ABS, or even the ability to start the car. That’s a serious hazard, especially if it happens while you’re driving. Things can go south quickly if overlooked-sometimes it starts with a warning light, but it can end up with your car stalling or not starting at all. If left unchecked, you risk damaging expensive parts like the engine control module (ECM), transmission control module (TCM), or even the wiring harness itself. Don’t put this off for later-the risks just aren’t worth it.

Repairing U0073

Based on what’s worked in the field and what the OEMs recommend, here’s what usually fixes a U0073 code:

Replace or recharge the battery if it’s weak or failing.
Repair or replace any damaged wiring or connectors in the CAN bus circuit.
Clean and tighten all ground connections related to the network.
Address any water leaks and dry out affected areas-sometimes you’ll need to replace corroded connectors or modules.
If a specific module is faulty, replace it and have it programmed to your vehicle (this usually requires dealership-level tools).
Update software or follow any TSBs provided by the manufacturer for your vehicle.

It’s best to start with something simple, like the battery and wiring, before moving on to the more expensive parts. When diagnosing u0073, always take a methodical approach to avoid unnecessary repairs.

Conclusion

To sum it up, U0073 means your car’s computers aren’t communicating properly, which can cause all sorts of problems-from warning lights to a no-start condition. This is a high-priority issue that can quickly turn into a safety risk if ignored. The most reliable way to resolve it is to start with the basics: check the battery, inspect the wiring, and look for any known issues from the manufacturer. If those don’t solve it, professional diagnostics may be needed. Don’t wait on this one-getting it fixed promptly is the safest and smartest move.

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