BMW E90: what to check by engine version, and why the diesel is its own story

The E90 is a case where “what will it cost to own” is settled not by mileage or bodywork but by which engine version is fitted. So the breakdown follows engine.

Diesel versions — the main question

The most important point in this article.

On some diesels of this period the timing chain sits at the flywheel end, that is, at the rear of the engine. Which means replacing it requires removing the transmission — and the labour cost differs dramatically from the usual.

Signs to catch before buying:

• A rattle on cold start — 1–3 seconds or longer. The most reliable symptom.
• Code P0016.
• Alongside it P0011 or P0014.
• Metal debris in the oil.

The mechanics are in the P0016 guide.

A cold start at inspection is mandatory. On this car that is not a preference but the only way to hear the most expensive problem available.

The rest of the diesel topics are standard: EGR (P0401), the particulate filter — see the DPF guide, injectors, and glow plugs (P0670–P0674).

Petrol versions

Valvetronic

Variable valve lift control instead of conventional throttling. The weak point is the actuator motor and its sensor.

Signs: the engine will not start or starts with difficulty, runs unevenly, limp mode, power limiting. Limp mode is covered separately.

VANOS

Cam timing control. Codes P0011, P0014.

As everywhere, the culprit is usually not the mechanism but the control solenoid and oil pressure. VANOS solenoids are cleanable, and at higher mileage that is routine. Covered in the cam phaser guide.

Oil filter housing gasket

A classic topic: oil leaks onto the accessory drive belt and the exhaust manifold.

Signs: a burnt oil smell after stopping, oil traces, sometimes a wisp of smoke from under the bonnet. Smells are covered in their own article.

The danger is not the leak itself but that oil destroys the belt.

Water pump

On some engines the pump is electric with its own control module. It fails suddenly, without warning, and produces immediate overheating.

What to watch: temperature in live data, not the gauge — the gauge is damped. Covered in the overheating guide.

Intake manifold flap

Produces unstable idle and lost low-end torque. Same logic as diesel swirl flaps — see the P2015 guide.

Common to all versions

Battery and registration. These cars run a power management system that tracks battery condition. Replacing a battery without registering the new one means the wrong charging profile and shortened life. The charging system is covered separately.

U-code cascades from voltage sags are the typical picture. Mechanics in the U0100 guide.

Wheel speed sensors — C0035–C0050.

Inspection order when buying

1. A cold start is mandatory. On a diesel it is the main check of the visit.
2. Read codes across every system, not just the engine.
3. Look for P0016, P0011, P0014.
4. Check the module roll call: who does not answer.
5. Warm-up temperature and the fan switch-on point.
6. Inspect the oil filter housing area.
7. Readiness monitors — all not ready means the memory was just cleared.

The full protocol is in the used car inspection guide.

In short

• Engine version, not mileage, decides the cost of ownership.
• On some diesels the chain is at the rear — replacement needs the transmission out.
• A cold-start rattle is the most expensive symptom you can hear for free.
• VANOS is usually cured by cleaning a solenoid, not replacing the mechanism.
• The oil filter housing leak is dangerous because of the belt, not the oil.

Download the app — codes across every system, freeze frames, and live data are read with an ELM327 adapter over Bluetooth SPP on Android.