HowTo: Convert M52TU Engine to MS43

First question to answer would be: Why do all this, when your engine is running fine?

The M52TU engine from BMW is almost the same as its successor, the M54 engine. Except for the throttle body and pedal it shares all sensors with MS43 powered M54.

It's not a complete plug & play operation to update the ECU from MS42 to MS43, but we try to make it as easy as possible with this guide.

Note: Currently we have no E39 available for measuring and testing, so all lengths and part numbers will be listed for E46. Please validate E39 part numbers on your own.

Install Electronic Throttle Pedal

Regardless of method used to adapt the M52TU wiring to MS43, you have to retrofit a fully electric throttle paddle.

Parts List

• Mounting plate:
  • LHD: 35 42 6 772 703
  • RHD: 35 42 6 772 704
• Accelerator pedal:
  • Automatic: 35 42 6 786 281
  • Manual: 35 42 6 786 282
• Connector and cabling:
  • Connector: BMW 61 13 8 383 300 (Tyco 1-967616-1)
  • Terminals: 12x Tyco 5-963727-1 (MQS Quadlock 0.35mm²)
  • Cable: 6m FLRy 0.35mm² (E46 chassis, others may vary)

Pinout

The electronic accelerator pedal (connector X11400) needs to be connected to MS43 (connector X60004) with six wires of about 1m in length for an LHD E46 chassis others may need longer wires due to the ECU box being on the other vehicle side or vice versa.

You can use any 0.35mm² cable since there is not much current used by the two potentiometers. We suggest using FLRy type wires with original colors from the table below.

Pedal Side Pin	Signal Name	Color	ECU Side Pin
X11400.1	M_FWG1	brown/green	X60004.7
X11400.2	M_FWG2	brown	X60004.12
X11400.3	U_FWG2	yellow/green	X60004.14
X11400.4	A_FWG1	white	X60004.8
X11400.5	U_FWG1	yellow	X60004.9
X11400.6	A_FWG2	white/green	X60004.13

The finished wiring for the electronic throttle paddle will look something like this when finished:

Engine Wiring Modification

For M52TU to work with MS43 ECU you have two options for the wiring. Both options are valid and you can decide whatever suits your needs better:

• Option A: Maintain M52TU engine wiring and work with adapters
• Option B: Update engine wiring to M54 and solder some cables

If you prefer not having to change the whole wiring loom itself or have soldered connections in the engine wiring, we would advise to stick with the M52TU wiring. Same goes for vehicles that came with an M52TU but never with an M54 like the E38 or if your wiring loom is in a very good condition.

Keeping the M52TU wiring needs an adapter for the throttlebody, while a full M54 wiring conversion needs soldering for the cluster signals and a 4mm² voltage supply line.

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Option A: Adapt M52TU wiring harness to full DBW throttlebody

The easiest approach make your engines wiring compatible to MS43 is to create two little adapters, one for the throttlebody and another one for the instrument cluster signals.

Cluster Signal Adapter

Vehicles equipped with M52TU and MS42 have 4 cluster signal wired through the ECU plug from connector X60003 to connector X60004.:

• Oil Pressure Switch
• Charge Control Light
• Oil Level Sensor Signal
• Engine Start Signal

These signal wires need to be depinned from the connectors housings and connected with each other. A very easy solution would be cutting them and solder them together, but that makes it impossible to remove the engine wiring in the future.

A better way is to keep the MQS terminal in place and make an adapter. For this adapter you need two female MQS quadlock 4 way connectors and two male ones with matching terminals.

Parts needed:

• 2x Female Connector: BMW 61 13 2 359 994 | Tyco 1241634-1
• 2x Male Connector: BMW 61 13 6 925 611 | Tyco 0-1452576-9
• 8x Male Terminals: 8x Tyco 5-963730-1 (MQS Quadlock 0.50mm² - 0.75mm²)
• 0.5-1m FLRy wire

The goal is to have a male to male connector that acts as a gender changer for the female connections you depinned previously, something like this:

The pinout doesn't matter as long as you maintain a straight 1:1 connection. To make things easier, here is a suggested pin assignment:

• Pin 1: Oil Pressure Switch (brown/grey)
• Pin 2: Charge Control Light (blue)
• Pin 3: Oil Level Sensor Signal (grey/blue)
• Pin 4: Engine Start Signal (black/yellow)

Now click the depinned terminals into the female connectors and secure the second locking mechnism. Once you are done it will look something like this:

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Option B: Change Engine Wiring Loom To M54

X6011 - Engine Signals - 8 way black connector

M54 Engine	Cable Color	MS42 Vehicle	Function
X6011.1	black	following	Starter Signal
X6011.2	green/brown	following	Terminal 15
X6011.3	brown/grey	X60004.11	Oil Pressure Switch
X6011.4	blue	X60004.13	Charge Control Light
X6011.5	grey/blue	X60004.21	Oil Level Sensor
X6011.6	black/yellow	X60004.02	Engine Start Signal

X6053 - Voltage Supply 8 way white connector

M52TU cars dont have seperated +12V lines for ignition coils and injection valves, so you have to combine pin 7 (red/yellow) with pin 2 (red/white/yellow).