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Electrical guides and mods

3 Lines On The Speedo

Three horizontal lines on the speedo LCD indicates that there is a fault in the gearshift system. There are a few reasons for this to happen.

Modification Details

This page ONLY covers the fortwo 450 (1998 - early 2007) & the Roadster


This is the symbol that will displayed on the speedo if a shifting problem occurs.

Generally the car will not start and no gears can be selected although there
have been cases where the car has driven fine despite the error showing.

If the car drives fine forwards and backwards, simply disconnect the battery for
10 minutes before reconnecting. This should clear the error from the car's memory.

What Can Cause It?

The smart gearbox relies on a lot of electronics to keep it working properly, it only takes one
part to misbehave to call up an error code. Causes can be one or more of the following:

Fuse Blown
Secondary Fuse/Relay Box Corrosion (600cc)
Faulty SE Drive
Stuck Gears
Weak Battery
Poor Earth Lead
Faulty Brake Lights
Incorrect Brake Light Bulb
LED Brake Light Bulbs
Faulty Gearbox RPM Sensor
Faulty Rear Light Loom (Roadster)
Faulty Gear Motor
Faulty Gear Position Sensor
Faulty Clutch Actuator
Chaffed Wires
Damage Wires
Stuck Clutch
Seized Gearbox
Faulty Relay
Split Reluctor Rings
Worn Clutch Fork
Solder Joint Failure
Faulty gearbox RPM sensor 
Gearbox Reteach
Canadian E-Box Failure
ECU Component Failure

This page goes into detail for each heading explaining how to fix each error.

Fuse Blown

This should be your initial go-to check for any electrical problems.
Check your fuses, in particular on the 700cc fortwo and Roadster, check fuse 30.
It's the power for the gearbox and the SE drive.

On the 600cc fortwo, check the secondary fuse box. Fuse 2.

Secondary Fuse Box Corrosion

On the 600cc fortwo (city car) there was a 2nd fuse box under the left hand seat.
It's prone to water ingress from leaks which can cause engine and transmission faults.

Checking, removing and cleaning the seconday fuse box can be seen here.

Faulty SE Drive

The gear change works on non contact hall effect sensors that are activated by a magnet
(much like a reed switch but a chip format). Gear changes should be clean, smooth and full
push or pull to the limit of the stick's travel before releasing. Hesitation during a gear change
or not pushing/pulling the stick to the full limit can cause this error code to appear.

It is unlikely that the magnet will lose its power but there have been cases where the
internal PCB of the SE Drive falls down. This can put the hall effect sensors out of reach
of the magnet causing the same problem. Usually this problem can also cause the
ignition switch to move away from the barrel making the car impossible to start.

The PCB could become faulty, I don't know how exactly but electrical components in general do fail sometimes.


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