BMW S0392: what “no communication possible with engine electronics” means

BMW fault code S0392 means “no communication possible with engine electronics”: your diagnostic tool, or another control unit, asked the engine control unit (the DME) for a reply and got nothing back. It tells you the DME is unreachable, not that it is broken. The cause often lies in power, earth, fuses, wiring or an interrupted programming session.

Seeing S0392 on a scan tool is unsettling. The car may not start, the gearbox may refuse to leave Park, and the first thing anyone mentions is a new engine computer. Before you spend money on parts, it helps to know what the code actually says and what it leaves out. At ATR Transmissies in Montfoort we see this code on BMWs that came in for what looked like a gearbox fault, so this page also covers the transmission side. You will learn what S0392 means, what usually causes it, how to diagnose it in the right order and what drives the cost.

What does BMW fault code S0392 mean?

S0392 is a communication fault, not a component fault. BMW’s diagnostic software describes it as “no communication possible with: engine electronics” (in some versions “motor electronics”). It is stored when a tester or another module tries to talk to the DME and the DME does not answer.

That difference matters. A normal fault code is set by a control unit that measures something itself and finds a value out of range. S0392 is set because nothing could be measured at all. The code names what went silent, not why. The DME might be dead, but it might just as well have lost its power supply, its earth, its connection to the data bus, or its coding.

The exact wording varies with model, year and software version. One BMW reads out “engine electronics”, another “DME” or “motor electronics”. The meaning is the same.

Why doesn’t a generic OBD2 scanner show S0392?

S0392 is a BMW-specific code, not a standardised OBD2 code. Codes that start with an S come from BMW dealer-level diagnostics such as ISTA and from tools that replicate BMW’s protocol. A generic OBD2 scanner only reads the emissions-related part of the engine control unit, so it will never show this code.

That explains a common situation. Someone plugs in a cheap scanner, sees nothing useful or cannot connect at all, and only a BMW-capable tool brings S0392 to the surface. Without that tool you also miss the codes that other modules have stored about the same event, and those codes are what point you in the right direction.

S0392 is not the same as P0392

This mix-up happens a lot. P0392 is a generic OBD2 code for “camshaft position sensor B circuit low, bank 2”: a low signal from one of the camshaft sensors. That is a completely different problem with a completely different fix. If you search on the number alone, you can easily end up chasing the wrong fault, so always check the letter in front of it.

What symptoms come with S0392?

The symptoms range from “will not start” to “drives, but will not shift properly”. What you notice depends on whether the DME is permanently unreachable or only drops out now and then.

• The engine does not start, or does not even crank.
• The car cuts out while driving and will not restart.
• The dashboard lights up with several warnings at once, often for systems that have nothing to do with the engine.
• The automatic gearbox or DKG stops shifting, stays in limp mode (emergency mode) or will not come out of Park.
• The diagnostic tool connects to other modules but not to the engine electronics.

If S0392 is only stored as an old, inactive entry in another module’s memory, there may be nothing wrong right now. Such entries can be left behind by an earlier session in which the car was asleep or the battery was flat. Always check whether the code is current before anyone starts taking things apart.

What causes S0392 on a BMW?

Because the code only says the DME is not answering, the cause can be anywhere in the chain: the supply to the module, its earth, the data bus in between, or the module itself. These are the directions that most often lead to the fault.

The fuse direction is not theoretical. BMW published a service bulletin (B120617) describing a no-start with S0392 stored where a 5 A fuse (fuse 83) had blown because the inrush current of the turbocharger coolant pump briefly exceeded its rating. Owners on BMW forums report similar finds, from a replaced battery pyro fuse to a loose earth on the cylinder head. Each of those cars showed the same code, and none of them needed a new DME.

A real case: an M5 F10 with both DMEs “in a coma”

The last two rows of the table are where our own work often ends up. We had a 2012 BMW M5 F10 with a DKG dual-clutch gearbox in the workshop that came in not running. The clutch of the DKG had already been replaced elsewhere, and after that repair a software update was run with ISTA. ISTA updates all control units in one session, which takes a long time, and this session froze at the two DMEs. From then on they would not communicate at all, and the memory showed S 0281 (no communication possible with digital engine electronics 2) and S 0392.

We read out both DMEs on the bench, which means opening the module and reading the data straight from the microcontroller on the circuit board. The software turned out to be intact. The coding was not: the modules no longer knew what they were or how they should behave. Once we restored the coding, the car started, and a test drive confirmed the DMEs kept working under load. The car was mechanically sound the whole time. You can read the full story in our case report on the BMW M5 with DMEs in a coma.

Can S0392 cause gearbox or transmission problems?

Yes, indirectly. S0392 is not a transmission code, but it often arrives with a transmission complaint. The transmission control unit (EGS on a BMW) relies on engine data such as engine speed and torque, which it receives from the DME over the data bus. When that data stops, the gearbox has nothing reliable to work with and goes into limp mode or refuses to shift, to protect itself.

To the driver, that feels like a broken automatic gearbox. With a ZF 8HP automatic transmission or a DKG you simply notice that nothing shifts any more, and the first idea is often a gearbox rebuild. That would mean replacing or overhauling a healthy transmission while the real fault sits in the electronics or the wiring. So this is the most important advice on this page: with S0392 stored, get the communication fixed first, before anyone touches the gearbox.

The reverse also exists. A BMW can have genuine transmission faults stored at the same time, such as the codes we discuss for this BMW F20 with 8HP fault codes 420634 and 420652. Then the gearbox itself does need attention. Telling those two situations apart is the core of a good diagnosis.

Which fault codes often appear with S0392?

S0392 rarely appears on its own. Once the engine electronics go silent, other modules report that they have lost contact too. You therefore often see a list of S codes at the same time, such as S 0281 for the second engine control unit on engines that have two, and codes for other units that cannot be reached, for example S 0235 for the electronic transmission control.

That pile of codes is not a disaster. It is information. The pattern tells you where the break is. If only modules behind the same gateway complain, that points somewhere else than when the whole car cannot reach anything. Find out what your symptom could mean in our overview of transmission fault codes.

How do you diagnose and fix S0392?

Work from the outside in: power, earth and wiring first, the module itself last. Replacing parts straight away is the expensive route, with no guarantee of a result.

1. Read the car with BMW-capable diagnostics, not a generic OBD2 scanner.
2. Record every fault code from every module, and note whether each one is current or stored.
3. Check the battery: resting voltage, voltage under load, and whether a replacement battery was registered.
4. Measure the supply and earth at the engine control unit, and check the related fuses and the DME relay.
5. Test the data bus wiring before concluding that the module is faulty.
6. Ask whether the car was recently programmed, coded or tuned. An interrupted session is a common cause.
7. Only when power, earth and bus check out, look at the module itself: reading it on the bench, restoring software or restoring coding.

What you can check yourself first

You can safely do a few things before booking the car in. Charge the battery or connect a proper battery support unit and try again, because a weak battery can make modules drop off the network. Write down when the problem started and what happened just before: a battery change, a jump start, a software update, water ingress after heavy rain or a car wash. That history often saves diagnostic time. Do not keep clearing codes and cranking the engine; it removes useful information and drains the battery further.

For garages

If you are a garage and a BMW will not talk to its DME, you do not always have to send the car to Montfoort first. With ATR Remote we can look along remotely and help you find where the communication breaks down.

What does fixing S0392 cost?

Nobody can put a reliable figure on it in advance. The cost depends entirely on where the break is, and anyone who quotes a price before diagnosis is guessing. These factors decide the final price:

• How much diagnostic time it takes to locate the break.
• Whether it stays at a fuse, an earth point or a connector, or whether wiring has to be replaced.
• Whether the module has to be opened to read and restore its software on the bench.
• Whether only the coding needs restoring, or the programming as well.
• How many modules are involved, and whether the car can still be driven to the workshop.
• Whether a genuine mechanical transmission fault turns up as well.

Contact us for a price indication based on your registration number and complaint.

FAQ about BMW fault code S0392

Can I read S0392 with a normal OBD2 scanner?

No. S0392 is a BMW-specific code that only shows up with BMW dealer-level software such as ISTA, or a tool that supports BMW’s own protocol. A generic OBD2 scanner reads only the standardised emissions part and will not display this code.

Does S0392 mean my DME needs replacing?

Not automatically. The code only says the engine electronics are not answering, not that the module is faulty. Power, earth, fuses, bus wiring and a failed programming session are all possible causes. Rule those out before ordering an expensive module, which would also need coding to your car.

Is S0392 the same as fault code P0392?

No. S0392 is BMW’s code for no communication with the engine electronics. P0392 is a generic OBD2 code for a low signal from camshaft position sensor B on bank 2. They have nothing to do with each other, so always look at the letter before the number.

Can I still drive my BMW with S0392?

Often not. If the engine electronics are really unreachable, the car usually will not start or it cuts out. If the code is only stored as an old entry in another module, the car may drive normally. Have it checked to see whether the fault is current before you rely on the car.

Can I just clear or reset S0392?

You can clear it, but that fixes nothing if the cause is still there. A stored, inactive S0392 left behind by a flat battery may stay away after clearing. A current S0392 comes straight back, because the DME still is not answering. Find the cause first, then clear the memory.

Can a flat or new battery cause S0392?

Yes, it can. Low voltage can make control units drop off the network, and a replacement battery that was never registered can upset the power management. Check and charge the battery first, because it is the cheapest cause to rule out.

What is the difference between S0392 and S 0281?

Both report a communication fault, but with a different unit. S0392 refers to the engine electronics, S 0281 to digital engine electronics 2, the second engine control unit on engines that have two. Seeing them together suggests the problem affects more than one module, such as a shared supply, a bus fault or a failed update.

S0392 on your BMW? Get the communication checked first

BMW fault code S0392 means no communication possible with the engine electronics. It is a communication fault, not a death sentence for your engine computer, and certainly not proof that your gearbox is finished. The gain is in the right diagnostic order, not in replacing expensive parts on a hunch.

At ATR Transmissies we overhaul automatic gearboxes, DSG and DKG transmissions and BMW xDrive transfer cases, and we work on the control units that run them. That combination of mechanics and electronics lets us tell quickly whether a complaint belongs to the gearbox or to the communication around it. Diagnosis comes first, and you decide what happens after you know what is wrong. Book your car in with your registration number, the complaint and any fault codes you have.