U0065: Vehicle Communication Bus E Performance
What to do
Everything may still work. Do not wait for it to get worse — that is precisely the wrong advice on this one, and it is the advice you will most likely be given.
Here is why. Your car's network is making errors and correcting them, which is why you notice nothing. A network that does this goes on to drop out occasionally, and then to fail.
So if you also have faults that come and go — a dashboard that lights up and clears — that is not a second problem. It is the same one, a stage further along.
And the difference matters enormously to what it costs to find. A fault that is present all the time can be measured today. A fault that happens once a week has to be caught, and catching it is among the most expensive things a workshop can be asked to do.
So ask for the network's error counters to be read now, while the fault is continuous. That is a specific, cheap and reasonable request.
And mention anything fitted to the car — a tracker, dashcam or insurance box — since anything added to a network is a well-known cause of exactly this, and unplugging it is a free test.
What this code means
Vehicle communication bus E is working, and not working properly. See U0011 for what a performance code means and U0064 for the intermittent case.
Those two are usually the same fault at two stages, and recognising that is the point of this page.
A marginal network makes errors long before it drops out. So the sequence over a vehicle's life is: errors, then occasional interruptions, then a failure — and a performance code stored alongside a scatter of intermittent lost-communication codes is not two problems. It is one, caught at the stage before and the stage after.
Which makes this the moment worth acting on, and the argument is the one from U0011 with the numbers behind it: the fault is present continuously now, and it is about to become present occasionally. A continuous fault can be measured. An occasional one has to be caught.
So the specific request is for the error counters to be read now rather than for the vehicle to be brought back when it gets worse — which is the usual and entirely reasonable-sounding advice, and here it converts a findable fault into an expensive one.
Causes are U0011's marginal list, with U0037's long stub the one that produces errors on wiring which measures perfectly.
Likely causes
Start here
- Poor wiring splice in an aftermarket installation · moderate
- Corroded or loose connector · easy
- Intermittent wiring fault · moderate
- Damaged data bus wiring · moderate
Less common
- Failed bus terminating resistor · specialist
- Low system voltage · moderate
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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