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BMW X4 X4 xDrive20i common faults.

2018–2021, SUV, petrol, 184 HP.

The fault list covers: B48B20, B48B20M1 engine, ZF8HP transmission.

What you save stays on this device only. My saves

7 fault write-ups. 6 important. 9 recalls.

If you know the year, pick it. Faults for other years drop out of the list.

Before you buy

Known faults

6 important faults

critical2

B48 and B38 petrol: the timing chain guide rail breaks

critical

Plastic guide rails hold the timing chain in place. On these engines the plasticiser in the plastic leaches out over time, the rail turns brittle and then breaks into pieces. The pieces land around the chain and further down, in the oil sump and on the strainer of the oil pump, and the leached plasticiser also deposits on that strainer. Two kinds of damage come from this: without its guide the chain starts to flap, and less oil reaches the engine through the narrowing strainer. The first sign is a rattling noise on a cold start that goes quiet after a few seconds or once the engine has warmed up. It is heard best on a fully cold start in the morning, because the chain tensioner needs time to tension the chain. The problem is reported above 60,000 km. Replacing the chain costs between 700 and 2,900 euro, and is typically four figures, because the chain can only be reached by removing several engine components.

above 60,000 km700–2,900 EUR

What to check

  • Start the engine fully cold in the morning and listen for the rattling noise
  • Ask whether the chain and the guide rail have been replaced, and ask for the invoice
  • Ask when the oil was last changed and how often the car was serviced
2 more steps in the write-up

Electric water pump: silent failure, immediate overheating

critical

In these engines the water pump is not belt driven but has its own electric motor. It gains on fuel consumption, but it opens a new failure path: the pump or its electronics often simply stops with no warning. Measured in the official complaints, the typical mileage is 161,000 km (a tenth of the complaints already at 81,000, a tenth only above 257,000 km). So the common wisdom of "around 100,000 km" is early: most of the failures happen between 130,000 and 250,000 km.

Show the rest

With a belt driven pump the flow weakens gradually, here the circulation stops in an instant. In urban traffic the temperature crosses the limit within minutes, the cylinder head distorts, and the repair is an engine rebuild.

Replacing a still good pump at around 120,000 to 150,000 km costs less than repairing an overheated engine. If the replacement is already in the service book, the pump has already been changed.

between 81,000 and 257,000 km

What to check

  • Watch the coolant temperature gauge after startup: it should settle evenly, not jump around
  • Standing still with a warm engine, listen for whether the cooling fan and the pump are working
  • Ask for a fault code read: codes pointing at coolant flow belong here
2 more steps in the write-up

expensive4

Oil filter housing gasket: oil leak onto the belt and the alternator

expensive

A rubber gasket seals the oil filter housing to the block. The gasket hardens over the years, and oil leaks from under the housing. The oil drips onto the drive belt and the alternator.

Show the rest

Three things can happen. The oil stretches the belt and it can jump off (on a single belt engine that means an instant loss of the water pump and the alternator); oil getting into the alternator destroys the windings; and oil reaching the hot exhaust smokes and gives a burnt smell, and the official complaints do include burning smells and smoke.

The leak is visible: five minutes on a lift settles it. The gasket itself is a cheap part; the labour, the ruined belt and the alternator take the money.

between 64,000 and 246,000 kmreported complaints only

What to check

  • On a lift look at the block surface around the oil filter housing: a wet, oily or oily dusty film
  • Look at the drive belt: an oily, cracked, stretched belt is the consequence of the leak
  • Look at the alternator housing from below: an oil trail indicates damage reaching the windings
2 more steps in the write-up

XDrive transfer case (ATC): binding in corners, plastic actuator gear

expensive

The heart of the four wheel drive in the longitudinal engine BMW X models (X3, X5 and the X1 E84) is the ATC transfer case. It has two faults, and you can feel both while driving.

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The first is wear of the clutch pack and the fluid: in a slow, tight corner (a car park, a roundabout) the car jerks and "hops", as if the drive grabbed and let go. You can also get a jerk when pulling away on a slope. The second is the plastic actuator gear: the position signal is lost, the brake, ABS and 4x4/DSC lights come on together on the dash, and a clicking is audible from the transfer case when you switch the ignition off.

Workshops often propose a full transfer case replacement straight away. But the plastic gear can be replaced on its own, and the wrong tyre size or a mixed set of tyres also imitates the jerking, because the transfer case then slips continuously. So clear up the tyres and the fault code first, before you pay for a transfer case replacement.

between 72,000 and 175,000 km

What to check

  • In a slow, tight corner (a car park) watch for jerking, binding and a "skipping" feel
  • When pulling away on light throttle, can you feel the drivetrain jerk
  • Watch the dash: 4x4, ABS, DSC and brake lights together point at the actuator
4 more steps in the write-up

Crankcase ventilation (CCV) in the valve cover: oil consumption, rough running

expensive

The crankcase ventilation leads the gas that forms in the crankcase back to the intake and separates the oil out of it on the way. If the system clogs or the membrane tears, the pressure cannot get away: it finds a way out past the seals, or it pushes the oil through the piston rings. This is where the oil consumption comes from, and the oil that appears around the valve cover gasket. In the other direction a faulty breather takes unmetered air into the intake, and that is what makes the idle rough, the throttle response hesitant and the running coarse. Starting also gets harder, and in an extreme case the engine stalls at idle. Two characteristic signs help: weak or absent suction at the oil filler with the engine running, and noticeably rough running around 3,000 rpm. The hose at the rear of the valve cover can also let oil out. The sound insulation then soaks itself with oil, and oil gets everywhere in the engine bay. On the six-cylinder engines the breather is built into the valve cover, so the repair is replacing the cover or the whole oil separator together with the hoses, between 80 and 900 euro.

between 80,000 and 150,000 km80–900 EUR

What to check

  • With the engine running unscrew the oil filler cap: weak or absent suction is a sign
  • Look around the valve cover and at the rear of the engine bay for oil traces
  • Watch the idle, and the rough running around 3,000 rpm
2 more steps in the write-up

ZF 8HP automatic: mechatronics unit and connector sleeve leak

expensive

The ZF eight speed automatic (BMW Steptronic 8HP family) has two faults, and you can feel both.

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The first is the mechatronics unit: the valve body and the control electronics in one. If the solenoids or the pressure regulation weaken, the gearbox jerks, the D/R engagement is delayed, it logs a gear ratio fault code, and finally drops into limp mode (often staying in 2nd or 3rd).

The second, and often misdiagnosed, is the connector sleeve of the mechatronics unit: the O-ring of the plastic sleeve ages, and ATF leaks from the side of the housing, exactly where the wiring harness enters. This is easy to mistake for a rear crankshaft seal. The trail starts from the driver's side of the housing, not from the clutch side.

On cars built in 2023 there was also a separate safety recall for a welding fault in the mechatronics unit. That is not the same as the wear related sleeve and the valves.

Check the fluid level, the area around the sleeve and the fault codes first; do not accept a "full gearbox replacement" quote straight away.

above 120,000 km

What to check

  • On the test drive watch for delayed D/R engagement, a jerk when shifting, and limp mode (a stuck gear)
  • Look at the driver's side of the gearbox housing where the wiring harness enters: an ATF trail from the sleeve is suspect
  • Do not confuse it with a rear crankshaft seal leak: the direction of the trail decides
3 more steps in the write-up

cheap repair1

Plastic charge pipe: it goes brittle and cracks at the throttle body

cheap repair

The maker builds the charge pipe out of plastic, and the coupler at the throttle body is the critical point. The material goes brittle from heat cycles, from boost pressure and from the heat of the engine bay, and then it cracks. Three things coincide here: the moulded coupler carries both pressure and movement, the vibration of the engine arrives here through the throttle body, and the spot gets continuous heat load. The crack starts on the inner radius of the coupler. The symptom is a loss of pressure under load: the engine pulls cleanly at part throttle but flattens out at full throttle, and a hissing noise is audible from the engine bay at the same time. A yellow drivetrain warning comes with it, which often disappears after a restart, and sometimes a brief limp mode. One thing is worth knowing: a clean fault memory does not rule the crack out. The pipe has no sensor of its own, so the control unit can only log a boost pressure fault, and the leak is intermittent, appearing only under load. At a viewing two things are visible without tools. On the inner radius of the coupler the hairline crack sometimes comes with dark staining, because the oil mist in the boost air escapes through it. For the same reason a greasy, dark ring can appear at the joint of the coupler. The crack is reported above 80 000 kilometres, and replacing the pipe costs between 100 and 400 euros, because the part itself is not expensive. The most common misdiagnosis against that is replacing the turbocharger, which costs an order of magnitude more, and a pressure test protects against it. The factory repair is the same plastic part, which can crack again at a similar mileage; replaced with an aluminium pipe this failure mode disappears, and the driveability does not change.

above 80,000 km100–400 EUR

What to check

  • Look at the inner radius of the coupler at the throttle body: the hairline crack sometimes comes with dark staining
  • Look for a greasy, dark ring at the joint of the coupler
  • On a motorway slip road at full throttle watch for the loss of pressure and the hissing noise
2 more steps in the write-up

Checklist

BMW X4 X4 xDrive20i

First what you would check on any car. Then the faults of this model.

Before you buy

Checklist

The printed sheet starts with what you would check on any car. What you tick stays on this device only.

On every car

Ask the owner

Faults of this model

vinkodex.com · Before you buy it, see what can go wrong.

Official recall9 recallsShow

The manufacturer fixes these for free at a franchised dealer. Ask with the VIN whether it was done.

Most recent: 7 July 2026

SR/02180/26Safety recallFire7 July 2026 · EU Safety Gate

The RSW22 starter with reinforced water tightness (RWT) may experience increased abrasion of the magnetic contact, causing deposits to build up at the lowest point inside the relay. These deposits may increase relay contact resistance, leading to starting failures or short circuits. If a short circuit occurs, either when attempting to start the vehicle or while driving due to vibration-related movement of the deposits, it could cause a thermal event and increase the risk of fire. The product does not comply with the Regulation on the approval and market surveillance of motor vehicles and their trailers, and of systems, components and separate technical units intended for such vehicles.

Remedy: Type of economic operator taking notified measure(s): Manufacturer Category of measure(s): Recall of the product from end users Date of entry into force: 07/07/2026

The authority's notice

SR/00551/26Safety recallFire30 January 2026 · EU Safety Gate

The failure concerns the RSW22 starter, type RWT (reinforced for watertightness). Increased abrasion of the magnetic contact can lead to the formation of deposits at the lowest point of the relay interior. This in turn can increase the resistance of the relay contact, causing accidental ignition or even short circuits, possibly leading to a thermal reaction and fire. The product does not comply with the Regulation on the approval and market surveillance of motor vehicles and their trailers, and of systems, components and separate technical units intended for such vehicles.

Remedy: Type of economic operator taking notified measure(s): Manufacturer Category of measure(s): Recall of the product from end users Date of entry into force: 30/01/2026

The authority's notice

SR/00568/26Safety recallFire30 January 2026 · EU Safety Gate

The failure concerns the RSW22 starter, type RWT (reinforced for watertightness). Increased abrasion of the magnetic contact can lead to the formation of deposits at the lowest point of the relay interior. This in turn can increase the resistance of the relay contact, causing accidental ignition or even short circuits, possibly leading to a thermal reaction and fire. The product does not comply with the Regulation on the approval and market surveillance of motor vehicles and their trailers, and of systems, components and separate technical units intended for such vehicles.

Remedy: Type of economic operator taking notified measure(s): Manufacturer Category of measure(s): Recall of the product from end users Date of entry into force: 30/01/2026

The authority's notice

SR/00584/26Safety recallFire30 January 2026 · EU Safety Gate

The failure concerns the RSW22 starter, type RWT (reinforced for watertightness). Increased abrasion of the magnetic contact can lead to the formation of deposits at the lowest point of the relay interior. This in turn can increase the resistance of the relay contact, causing accidental ignition or even short circuits, possibly leading to a thermal reaction and fire. The product does not comply with the Regulation on the approval and market surveillance of motor vehicles and their trailers, and of systems, components and separate technical units intended for such vehicles.

Remedy: Type of economic operator taking notified measure(s): Manufacturer Category of measure(s): Recall of the product from end users Date of entry into force: 30/01/2026

The authority's notice

23V211000SEATSSEATS29 March 2023 · NHTSA (USA)

BMW of North America, LLC (BMW) is recalling certain 2019-2021 330i, 330i xDrive, M340i xDrive, 2020-2021 X3 sDrive30i, X3 xDrive30i, X3 M40i, X3M, 2021 X3 xDrive30e, X4 xDrive30i, and X4M vehicles. The seat frame may not have been welded properly to the seat rails.

Risk: An improperly welded seat frame may not properly restrain the occupant during a crash, increasing the risk of injury.

Remedy: Dealers will replace the seat frame and back rest, free of charge. Owner notification letters were mailed May 22, 2023. Owners may contact BMW customer service at 1-800-525-7417.

The authority's notice

21V199000FUEL SYSTEM, GASOLINE:STORAGE:TANK ASSEMBLYFUEL SYSTEM, GASOLINE:STORAGE:TANK ASSEMBLY24 March 2021 · NHTSA (USA)

BMW of North America, LLC (BMW) is recalling certain 2021 X3 sDrive30i, X3 xDrive30i, X3 M40i, X3M, and X4, and 2021 X4 xDrive30i vehicles. The inlet check valve weld may fail, allowing the filling pipe to separate from the fuel tank.

Risk: Fuel may leak through the failed weld, increasing the risk of a fire.

Remedy: BMW will notify owners, and dealers will replace the fuel tank, free of charge. The recall is scheduled to begin May 17, 2021. Owners were also contacted by telephone. To date, all repairs have been done. No further owner notification letters will be sent. Owners may contact BMW customer service at 1-800-525-7417.

The authority's notice

20V598000BACK OVER PREVENTION: SENSING SYSTEM: CAMERABACK OVER PREVENTION: SENSING SYSTEM: CAMERA30 September 2020 · NHTSA (USA)

BMW of North America, LLC (BMW) is recalling certain 2020-2021 X3 sDrive 30i, X3 xDrive 30i, X3M 40i, X3 xDrive 30e, X4 xDrive 30i, X4M 40i, 530i, 540i, 540i xDrive, M550i xDrive, M5, 550e, 550e xDrive, and 550e iPerformance vehicles. A small portion of the rearview image may be slightly obscured. As such, these vehicles fail to comply with the requirements of Federal Motor Vehicle Safety Standard number 111, "Rear Visibility."

Risk: If the driver relies on only the rearview camera image, the reduced rearview image view can increase the risk of a crash or injury.

Remedy: BMW will notify owners, and dealers will inspect and, if necessary, program the rearview camera with updated software. The recall began November 18, 2020. Owners may contact BMW customer service at 1-800-525-7417.

The authority's notice

A12/00988/23Safety recallInjuriesno date · EU Safety Gate

The driver's and/or passenger's seat could break the frame rail that connects the seat to the guide rails on the vehicle floor. The stability of the seats may be affected, increasing the risk of injury in case of an accident. The product does not comply with the Regulation on the approval and market surveillance of motor vehicles and their trailers, and of systems, components and separate technical units intended for such vehicles.

Remedy: Type of economic operator taking notified measure(s): Manufacturer Category of measure(s): Recall of the product from end users Date of entry into force: Unknown

The authority's notice

SR/03830/25Safety recallFireno date · EU Safety Gate

Water may come into contact with the starter relay and gradually cause corrosion. This could affect the electrical connection inside the relay and make the engine difficult to start. It may also result in a short circuit and could cause the starter to overheat leading to a fire when the vehicle is in motion or when it is parked with the ignition off. The product does not comply with the Regulation on the approval and market surveillance of motor vehicles and their trailers, and of systems, components and separate technical units intended for such vehicles.

Remedy: Type of economic operator taking notified measure(s): Manufacturer Category of measure(s): Recall of the product from end users Date of entry into force: Unknown

The authority's notice

Engine and transmission

2 engines · 1 transmissions

B48B20

145 kW (197 HP) · petrol

ZF8HP · 8-speed automatic, longitudinal (ZF 8HP45/50/51)

automatic · 8 speed

Torque limit500 Nm
MakerZF

We built the code from the model and the gear count. The factory sheet does not state it. More than one engine code is possible. The fault list shows the faults of each.

Variant data

What is in this version

Factory data

Trim
X4 xDrive20i
Body
SUV
Fuel
petrol
Transmission
automatic
Engine size
1998 cc
Power
135 kW (184 HP)
Drive
AWD
Production
2018–2021

Factory service interval

The manufacturer specifies this for this version. Of the mileage and the time, the one that comes first is the one that counts.

  • Air filter

    • 60,000 km or 4 years

  • Cabin (pollen) filter

    • 30,000 km or 2 years

  • Brake fluid change

    • first: 3 years, then 2 years(first change at 3 years, then every two years)

  • Engine oil and oil filter (BMW condition-based service)

    • LongLife25,000 km or 2 years

  • Automatic gearbox oil (ZF 8HP / 6HP)

    • 160,000 km

  • Spark plugs, petrol

    • 60,000 km or 6 years
All G02 versions

Information, not an expert opinion

We write the descriptions, and we put the source next to them. A person reviews them before they go out. They are still information, not a technical expert opinion.

  • A fault on the list does not mean the car you are looking at has it.
  • A fault missing from the list does not mean the model is fault-free. Write-ups are made model by model. Not all of them are done.
  • You decide whether to buy. This is no substitute for an inspection. That needs a workshop and a history check.
Details in the terms