U1000 Code: Meaning, Symptoms, Causes, Fixes, And Repair Cost

If you're getting a U1000 trouble code, then this guide contains everything you're looking for, such as the main symptoms, the meaning, and how to fix it.

The U1000 code appearing on your OBD II code reader is a little indistinct. It’s, in general, defined as Communication Network Malfunction.

However, it’s a manufacturer-specific code. Each manufacturer defines it ever so slightly differently. See a list of affected car makers below.

If your car is showing a U1000 code, I will walk you through what’s going on. The specific root cause can be tricky to narrow down.

If you get stuck, don’t be afraid to take your car to a trusted local mechanic.

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Manufacturer-Specific Code

U1000 Trouble Code

The U1000 OBD II code only affects certain manufacturers. These typically include:

  • GM (Chrysler, GMC, Chevrolet, and Buick)
  • Nissan (including Infiniti)
  • Isuzu (owned by Mitsubishi)

While this “communication malfunction” could affect any car, other manufacturers use different fault codes.

DTC U1000 Meaning

DTC U1000 Trouble Code

The U1000 engine code meaning is “Communication Malfunction.”

That doesn’t mean there’s a problem with the hands-free system! It refers to an issue with the CAN.

The Communication Area Network is a vehicular data bus network. It forms part of your car’s broader ECU (Electronic Control Unit).

The CAN is responsible for linking all the individual modules into one cohesive unit. If you own a new car, it could have over 100 separate modules to connect. That’s a big responsibility!

Nobody thinks about the CAN very often, but it’s always there, working away in the background. Without it, your vehicle would scarcely shift out of Park.

Depending on your vehicle brand, you might see any of the following specific codes:

  • CAN Communication Circuit
  • CAN Communication Line – Signal Malfunction
  • Class 2 Communication Malfunction Conditions
  • Class 2 Communication ID Not Learned

Don’t worry – they’re all different ways of saying the same thing.

What Are The Symptoms Of A U1000 Code?

car check engine light on

The main symptom you’ll see is, of course, the Check Engine Light and the presence of the code on the OBD II reader. 

In many cases, this will be the only tangible symptom.

Everything depends on the gravity of the issue. The automobile could have detected a minor interruption in the exchange of messages between the two components. If it was a brief, unimportant irregularity, it will keep functioning without any changes.

If, though, the CAN represented a complete failure to transfer specific information, it would lead to a bigger issue. For example, if the Engine Control Module (ECM) didn’t send data on its engine speed to the Transmission Control Module (TCM), the car wouldn’t know when or if to shift.

Because of this, the potential symptoms are boundless. However, a malfunction in the CAN often leads to:

  • The engine stalling
  • Hesitation and jumping
  • Poor acceleration (low power)
  • Failure to start

These symptoms can be similar to those caused by multiple misfires and fuel injection issues. Watch out for that.

What Causes A U1000 Code?


First of all, let’s make this clear: a U1000 code isn’t your fault! There’s nothing you can or could have done differently to prevent it from coming up.

A U1000 fault code most often stems from a defect in the manufacturer’s electronics design.

Over time, glitches or physical damage could lead to the U1000 code. It often stems from:

  • Improperly coded modules, leading to a bug or glitch
  • The intrusion of dirt, debris, and water, causing failure
  • Electrical problems (such as rusted connections or bad grounds)

You’ll usually find other codes stored alongside the U1000 DTC. These might point you in the right direction, especially if they’re related to other ECU modules.

If the OBD II code reader only shows the U1000 code – and nothing else – try wiping the stored codes. Restart your car and run it for a few minutes to see if the code reappears.

Sometimes, the code gets thrown out as an anomaly. One module may have lost connection with another for just a moment, for example, before everything went back to normal.

How Do I Fix My U1000 Code?

car technician holding the wrench

Whenever you find that any engine code is present, it requires further investigation.

That assumes you’ve eliminated the possible anomalous reading by wiping the codes and restarting the car. You should also have a quick look at past Service Bulletins (more on those below).

Most drivers can’t conduct an extensive ECU examination on their own. It’s possible that you may need professional mechanics to handle it.

Leave this one to the professionals. Messing up while working with your car’s Control Modules could lead to a disaster (such as wiping them!).

In short, once you’ve eliminated the quick fixes, you can’t avoid needing a professional diagnosis. It’s the only way your car will get back to normal.

Even if you aren’t noticing any symptoms other than the Check Engine Light, don’t hesitate. If you leave it, it’ll probably get much worse and do much more damage. It’s not worth it!

DTC U1000 Repair Cost

Man Counting Money

There’s no way to sugarcoat this: ECU electrical investigation is an expensive job. Unfortunately, it needs doing, so you’re left with little choice.

It’s difficult to estimate the damage to your bank account in advance. Nobody knows how bad the problem is until someone delves into your ECU code and infrastructure.

Have a figure of around $1,000 in your head as a minimum threshold. Sadly, it could be more, especially if it’s established that you need a new module (or two!).

Ask for quotes before you send your car to your chosen shop.

An excellent way to save money is to go straight to the automotive electricians. You might be staggered by the labor rates (which tend to be much higher than the average mechanic’s).

However, a typical car mechanic most likely lacks the abilities for ECU reprogramming or replacement. They will outsource the task to automotive electricians they commonly collaborate with. When you retrieve your car, you will be charged the expert fee in addition to a slight increase (typically around 20%).

Thus, it’s much cheaper to go to an automotive electrician in the first place.

One last point on cost: check for official Service Bulletins. Nissan, in particular, has issued a fair amount of Communication Network recalls. These often need fixing via free software updates.

If you find your car is affected by a U1000 recall, you could be in luck. The problem might be solved and fixed for free.

Check online (the NHTSA is a good place to start) before giving your local dealership a ring. Again, double-check it’s free before you commit!

Conclusion – Trouble Code U1000

Diagnostics of car failures: an electrician in gray clothes is sitting in the car's interior and reading the trouble codes from a portable auto scanner with OBD2 interface.

In conclusion, go through the following steps after finding a U1000 code. Doing this will potentially reduce the amount you’ll pay.

  1. Use your OBD II code reader to wipe the codes and then restart the car and drive it for a few minutes. Check to see if the U1000 code returns. If it doesn’t, it may have just been a glitch. Of course, if it does come back, there’s a genuine, consistent problem.
  2. If that fails, check for Service Bulletins. Enter your registration plate or VIN on any internet site to check. You might find one issued for your car regarding the Communications Network of your ECU. Call your local dealership and see if they’ll fix it for free!
  3. Finally, head to an automotive electrician and prepare to pay a not-insignificant sum for diagnosis and repair. Follow their professional advice, and you should be back on the road in no time.

The U1000 isn’t usually too severe – but it could be. It’s so generic that it’s almost impossible to say for sure either way.

Don’t put it off. Get it fixed as soon as possible. Your car and your wallet will thank you later!

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Benjamin Kitchen

Ben is an IMI-qualified light vehicle technician from England with experience in a fast-fit garage. He aims to help drivers worldwide with common automotive problems. You’ll often find him working with his 1.2 Vauxhall Corsa. It may have a tiny engine, but in eight years it's never once let him down!