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Before you buy a used BMW Serie 3 (G20/G21).

2019–2026 · Petrol / Diesel / Plug-in hybrid · 7 engines

Taken only from Testigo's sourced sheets. Use it to question the seller and on the test drive: it does not confirm that any particular car is affected.

BMW Serie 3 (G20/G21), real photo of this generation
Vauxford · CC BY-SA 4.0 · Wikimedia Commons · Photo source

The essentials.

Typical faults by engine

The period and mileage are those mentioned by each sheet's sources. They are not a maintenance interval and do not predict that any particular car will fail.

All versions

Sheets the catalogue links to all 7 of its engines.

  • ZF 8HP oil level, leaks and harsh shiftsAutomatic gearbox
    Period mentioned
    2009–2026
    Mileage mentioned
    The sheet does not mention a mileage.

    Applies if: Only if fitted with the automatic gearbox described in the record.

318i / 320i / 330i (B48) · 318d / 320d (B47) · 330d / 340d (B57) · M340d (B57, 3.0)

318i / 320i / 330i (B48) (Petrol) · 318d / 320d (B47) (Diesel) · 330d / 340d (B57) (Diesel) · M340d (B57, 3.0) (Diesel)

330e

Plug-in hybrid

M340i (B58, 3.0)

Petrol

These also apply, described above: B-engine coolant leaks and EGR cooler

M3 (G80/G81, S58, 3.0)

Petrol

We have no faults specific to this engine, only those common to every version.

Which engine has the fewest documented faults?

Documented faults and recalls by engine for the BMW Serie 3 (G20/G21)
EngineDocumented faultsRecalls
318i / 320i / 330i (B48)Petrol21 with conditions2
318d / 320d (B47)Diesel21 with conditions2
330d / 340d (B57)Diesel21 with conditions2
330ePlug-in hybrid21 with conditions2
M340i (B58, 3.0)Petrol32 with conditions2
M340d (B57, 3.0)Diesel21 with conditions2
M3 (G80/G81, S58, 3.0)PetrolFewest documented11 with conditions2

According to the data we have, the engine with the fewest documented faults is the M3 (G80/G81, S58, 3.0) (Petrol).

By fuel type, the ones with the fewest documented faults are: Diesel, Plug-in hybrid.

We only count the sourced sheets we have. An engine with fewer is not guaranteed to be more reliable: it may have been studied less or sold in smaller numbers.

Official recalls: ask before you pay

A recall existing does not mean this car is affected or that it is still outstanding: it depends on the chassis number, the market and the production date.

  1. Ask the seller for the chassis number (VIN): it has 17 characters, appears in the car's documents and can usually also be seen at the base of the windscreen.
  2. Ask an official BMW dealer, or the brand's official website if it lets you check by chassis number, whether each recall has been done or is still outstanding for that VIN.
  3. Manufacturer recalls are normally carried out free of charge by the official service network. If one is outstanding, ask for it to be done before you close the sale.
RSW22 starter motor that fails to crank or short-circuits (BMW 2020–2026)Electrical and electronic systems

How to check it: Ask a BMW garage to check with the VIN whether any of those campaigns is outstanding, especially if the car has already failed to start.

View full entry
Water in the starter motor: no start or the starter stays engaged (BMW 3, 5 and 7 Series)Electrical and electronic systems

How to check it: Ask a BMW garage to check with the VIN whether either campaign is outstanding; if the starter keeps turning or you smell burning, switch off and do not leave the car next to buildings.

View full entry

On the test drive: what to look and listen for

Taken from each sheet's symptoms and checks. You can tick off what you have already looked at: it is saved only in this browser.

0 of 4 checked

Cooling / EGR

  • Look out for: Coolant loss with a low-level warning, coolant or oil residue at the rear of the engine; on diesels, internal coolant loss with no visible leak (EGR cooler).

    Ask them to check: Check the coolant level, look for leaks under the water pump and at the oil filter housing, and on diesels confirm by VIN whether the EGR cooler campaign was done.

High-voltage battery

  • Look out for: Usually none before failure. In rare cases, a battery short-circuit with a fire risk, especially while charging.

    Ask them to check: Confirm by VIN with BMW that the battery recall has been done; if not, do not charge the car until it is checked.

Automatic gearbox

  • Look out for: Harsh shifts (especially engaging D and 1st to 2nd), slipping or jerking; oil leaks from the pan, the mechatronic connector sleeve or the seals.

    Ask them to check: Check the oil level with the official procedure (correct temperature and engine running), look for leaks at the pan, connector sleeve and seals, inspect the pan for impact damage and review adaptation values with ISTA.

Powertrain and engine management

  • Look out for: With Start/Stop off and the car stationary, after about 30–50 seconds at idle there is a slight jolt or change in engine speed that feels like a misfire; no warning light and no fault codes.

    Ask them to check: If there are no codes or warning lights, tell the garage BMW considers it normal operation (SIB 12 11 26) to avoid replacing coils, spark plugs or injectors.

Sources

Every fact on this page comes from these Testigo sheets and their original sources. Sources are not checked in real time.

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