Engine code
N42 · 1.8 and 2.0 liter · 4-cylinder with Valvetronic · 2001-2004 · E46 316i, 316ti, 318i, 318Ci, 318ti
The N42 is a 4-cylinder petrol engine with Valvetronic variable intake valve lift, built for the E46 3 Series. It came in two sizes, the 1.8 liter N42B18 and the 2.0 liter N42B20. BMW's service documents say the N42 was later redesigned and renamed N46, and that the 1.6 liter N40 got the same treatment and became the N45. The N42 was not sold in US-market BMWs, per BMW's own vehicle lists (data to December 2019), so this is a short guide.
This guide only states what BMW's own documents establish. Ownership opinions, failure rates, costs and tuning potential are marked as not established.
N42 At a Glance
| Question | Practical answer |
|---|---|
| Where you find it | E46 3 Series: 316i, 316ti, 318i, 318Ci and 318ti. BMW's exhaust system overview says the N42B18 arrived in early 2001 in the E46 Compact, and BMW's service bulletins cover N42 cars built from April 2001; BMW's parts catalog ends the N42 types in 02/2004 and 03/2004. |
| Sold in US-market BMWs | Not sold in US-market BMWs, per BMW's own vehicle lists (data to December 2019). All 30 N42 vehicle types BMW lists are for other markets. |
| Engine sizes | 1.8 liter N42B18 and 2.0 liter N42B20 |
| Factory output | N42B18: 85 kW at 5,500 rpm and 175 Nm at 3,750 rpm. N42B20: 105 kW at 6,000 rpm and 200 Nm at 3,750 rpm. |
| Valvetronic | Yes. BMW's engine control overview describes the N42 with a separate Valvetronic control unit, which the N46 later folded into the main engine computer. |
| Engine oil | 4.25 liters with a new filter. Check the owner's manual for the grade; BMW's current oil suitability list includes the N42. |
| Replaced by | N46, which BMW describes as the redesigned N42. |
| Reliability, cost to own, power potential | Not established yet. We are still researching this engine. |
| Known service bulletins | Two BMW bulletins cover early E46 cars with the N42. See Known Failure Points and Service Items. |
Technical Specifications
| Specification | Detail |
|---|---|
| Cylinders | 4, petrol |
| Displacement | N42B18: 1,796 cc. N42B20: 1,995 cc. |
| Bore x stroke | N42B18: 84 x 81 mm. N42B20: 84 x 90 mm. |
| Compression ratio | N42B18: 10.25:1. N42B20: 10.0:1. |
| Maximum engine speed | 6,500 rpm, with 6,300 rpm as the permitted constant speed (BMW workshop data) |
| Valvetrain | Valvetronic variable intake valve lift. Camshaft phasing (VANOS) and valve count: Not established yet. |
| Power and torque | N42B18: 85 kW, 175 Nm. N42B20: 105 kW, 200 Nm. See At a Glance for engine speeds. |
| Engine management | Digital engine electronics ME 9.2 with an external Valvetronic control unit |
| Emissions | Euro 3 and Euro 4 versions appear in BMW's data, depending on model and date; the exhaust overview lists a secondary air system on Euro 4 versions. |
| Engine oil capacity | 4.25 liters with filter change |
| Coolant, firing order, valve count | Not established yet |
What the N46 Changed
BMW's N45/N46 documentation lists these changes against the N40 and N42: a cast crankshaft, geometrically modified connecting rods, a modified cylinder head cover, profile-milled drive gears on the balance shaft, and spark plugs with a modified centre electrode. On the N46 the Valvetronic control unit moved into the engine computer.
Known Failure Points and Service Items
These are the only two N42 bulletins we have read. Anything else about N42 failures is not established yet.
01 Valvetronic control unit output stage, early E46 cars
BMW service bulletin 11 01 02 (814) covers E46 cars with the N42 built from 1 April 2001 to 1 October 2001. The cause BMW gives is a hardware defect in the Valvetronic output stage. The symptom is an occasional Check Engine light with reduced power, and the engine computer logs fault DME-2860. BMW's remedy was a modified Valvetronic control unit, part number 11 37 7 516 809. Warranty reimbursement under that bulletin ended in October 2004.
In BMW's parts catalog (data date December 2019) that number was discontinued in 10/2003 and replaced through 12 14 7 532 949 by 12 14 7 527 313, which the catalog shows as current.
Watch for: a warning lamp with reduced power that clears after the engine is restarted.
02 Valvetronic plausibility fault after warm-up, E46 built 09/2001 to 02/2002
BMW service bulletin 12 01 02 (841) covers E46 cars with the N42 built from September 2001 to February 2002. The problem sits in a three-second transition right after warm-up, when the engine hands over from throttle control to Valvetronic. Held at light load through that window, the engine computer could falsely log a Valvetronic plausibility fault (DME-27CE) and go into limp mode. Per BMW, that shows up as an idle near 1,200 rpm, less power, slower throttle response and the engine power warning lamp. BMW's remedy was to reprogram the engine computer with diagnosis software release CD29.0 or higher.
Watch for: a high idle after warm-up, flat throttle response and a warning lamp on a car from that build window.
Reliability Verdict, Power Potential, Cost of Ownership
Not established yet. We are still researching this engine. No BMW document we read gives a failure rate, a repair budget or a safe tuning output for the N42.
Common Questions
What BMW has the N42 engine?
The N42 was fitted to the E46 3 Series, as the 316i, 316ti, 318i, 318Ci and 318ti, from 2001 to 2004. It was not sold in US-market BMWs, per BMW's own vehicle lists (data to December 2019).
How much oil does an N42 take?
BMW's workshop data gives 4.25 liters for an oil change with a new filter element.
Does the N42 have Valvetronic?
Yes. BMW's emissions data sheets list Valvetronic for the N42B18 and N42B20 in the E46.
What replaced the N42?
The N46. BMW's service documents describe the modified N42 as now called N46, in 1.8 and 2.0 liter versions.
Sources
- BMW Service Information bulletin 11 01 02 (814), Valvetronic control unit output stage fault, E46 N42.
- BMW Service Information bulletin 12 01 02 (841), faulty engine computer data in the Valvetronic monitoring function, E46 N42.
- BMW emissions test nominal values sheets for the E46 316ti, 316i, 318i, 318Ci and 318ti (enclosures to bulletin 00 01 02 (800)).
- BMW service documentation, engine control for N45 and N46 (11 01 04 (068)), and the exhaust system overview for N40, N42, N45 and N46.
- BMW workshop technical data for the N42, group 11: engine in general and oil supply.
- BMW parts catalog, data date 12 December 2019 (vehicle types, build dates, supersession).
- BMW oil suitability list for BMW Group engines, edition 09/2025.
- Wikipedia, BMW N42 (cross-check of power figures only).
