U0076 High Generic / SAE

U0076: Control Module Communication Bus D Off

Network and Communication Bus Signal and Bus Off Emissions related

What to do

Before anything else, have the battery and charging system tested. That is not a delaying tactic — it is very often the whole answer.

One of your car's computers has deliberately stopped talking to the network — see U0073 for why that is protection rather than failure.

But here is the cause worth eliminating first, because it is cheap and it is easy to miss. The computers need a steady supply to put the right voltages on the network. As the battery weakens, those voltages fall with it — and below a point, messages start failing. Enough failures and the computer withdraws.

So a tired battery causes this, and it causes it at the worst moment: while starting, when the voltage is lowest.

If your car stores a batch of faults every time you start it, and the battery is a few years old or the car has been slow to start, that is very likely the entire explanation — and the network is perfectly healthy.

Say so if the starting has changed at all. A battery test costs almost nothing and a network diagnosis does not, and doing them in that order is worth real money.

What this code means

A module has taken itself off communication bus D. See U0073 for what bus off means.

One cause deserves to be eliminated before any wiring is touched, because it is cheap to check and it produces this code on a network with nothing wrong with it: low system voltage.

A transceiver holds the bus at defined levels using its own supply. As system voltage falls, the levels it can produce fall with it — and below a point, transmissions start failing. Failed transmissions increase the error count. Enough of them, and the module withdraws.

So a weak battery produces bus off codes, and it produces them at the moment the voltage is lowest: cranking. A vehicle that stores a handful of bus off and lost-communication codes every time it is started, on a battery that is on its way out, is describing exactly this — and the network is entirely healthy.

Which makes the sequence worth insisting on: test the battery and charging system before the network. They are cheap, fast, and they are the difference between a battery and a diagnostic bill.

The stored conditions confirm it. Codes logged consistently at low voltage, or during cranking, point here rather than at the wiring — see U0070, which is the same cause seen from the other side.

Likely causes

Start here

Less common

Another module holding the bus down · specialist
Failed power or earth supply to the module · 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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The car — make, model, year and engine. The same fault behaves differently on each.
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