If the Battery is not charging correctly, is not holding its charge (is flat) or the battery light is on it could lead to a number of issues.

• Faulty alternator
• Faulty battery
• Loose / Missing earth strap

You can check/test for the following resolutions:

• Test the alternator output using a multimeter, it should read approx 12.5v at rest and up to 13.5v when the engine is running.  If it's found to be faulty, replace the alternator - we have a guide on this site.
• Check the battery condition, this can be done usually free-of-charge at any motorfactors.  If faulty, replace the battery. A guide is found on this site.
• Check the earth straps around the car for fraying / tightness. One often missed is the main earth from the gearbox to the chassis.

Uneven acceleration, which feels like the turbo is pulsing, can be attributed to:

• A crack in the turbo manifold
• Broken (snapped) turbo studs
• Excessive turbo boost
• Split/disconnected vacuum hose to the wastegate

Other symptoms which may be experienced are:

• Excessive oil use
• Generally very poor acceleration
• Louder than normal exhaust note (akin to a VW beetle!)
• Poor economy

The wastegate arm is pre-set to the turbo, however if this is altered it can cause irregular behaviour.  This should never be altered, but it used to be common to adjust the arm to increase power.

Do ensure that all pipes are connected to the wastegate (we have a guide showing the arrangement of the pipes). 

Failing that, the turbo needs to be looked at.  If it is problematic then the only resolution is to replace the turbo manifold. You will probably struggle to find one for sale on its own, so you may have to replace the whole unit.

If you have a 600cc smart, look for the mk6 turbos (2002 model), as these had a modified reinforced bridge to try to resist the cracking.

Three lines on the dash indicate a 'Gearbox communication fault' or a 'Shifting system fault'.

Firstly it could just be a glitch... they do happen. Turn the car off and on again and see if the issue is resolved.

Other potential issues could be:

• Sticking clutch actuator
• Faulty or sticking gear selector motor
• Faulty gear position sensor
• Excessive clutch wear
• Loose/broken connection to the actuator/motor/sensor
• Damaged wiring where the loom passes under the intercooler duct

For a quick fix, you can try:

• With engine off and handbrake off and in reverse, rock the car backwards and forwards to free up the gears. Lubricate the gear actuator - see the guide on this site - replace gear selector motor, replace gear position sensor (we also have a guide for this) located in the fortwo gearbox page.

If you experience 6 dashes flashing in the mileage display, it is usually accompanied by a flashing fuel gauge display, and a flashing temperature gauge.

It would indicate a communication fault from your ECU or SAM unit, so firstly, check these cables.

It could also indicate:

• SAM and ECU are not correctly paired
• Water damage in the SAM unit

The resolution, if it's not loose wires, would be to replace the SAM unit and pair it to the ECU. Sadly this is not a cheap option, but it is a fairly serious fault.

If your ESP, ABS and brake warning light (handbrake light) stay on when driving it means that your safety systems are not running.

This could simply due to a dirty ABS sensor or reluctor ring, in which case remove the wheel and spray liberally with brake cleaner and use a wire brush for the stubborn deposits.

You might notice that the rings are cracked, in which case, this would also cause the lights to come on, and they will need replacing. 

If this is not the issue, then you need to look at the possibility of:

• Steering angle sensor out of alignment (have you recently swapped your steering wheel over?)
• Faulty steering wheel cartridge.
• Faulty Lateral Acceleration (Yaw) sensor

If the wheel is out of alignment, this is due to the cartridge moving when not connected to the steering column, which can easily happen if you have changed your wheel over. You will not be able to reset this by hand; it will require a trip to the dealers or an independent to have it reset on the star/winstar machine.

If the cartridge is faulty (air bag detonation will cause this), then it will need to be swapped out. The cartridges are common across all of the 700cc cars, so find the cheapest working wheel you can!

The lateral acceleration sensor detects the motion of the car relative to its direction.  These do fail, and instead of ignoring the sensor it will restrict the behaviour of the car. The sensor cannot be fixed, only replaced.

Fast flashing indicators is usually attributed to a blown indicator bulb on that side.

If they only flash fast when indicating left, then check the indicator bulbs on that side.

It might be that the connection of one of the bulbs is weak, whether in the bulb holder or the wiring to it.  To rectify you can either replace the lamp cluster or wire in a new connector.

We have noticed that cars fitted with a SAM unit (698cc models) have an issue where if you fit LED indicator bulbs, this causes a resistance issue which will also cause the bulbs to flash at a double rate. You can either wire in an additional resistor, but to be honest, you might as well just remove the LED bulbs and replace with conventional ones.

Normal running temperature for the fortwo is at '3 blobs', or 80-85 degrees. It should reach this temperature within 10-15 minutes of normal driving.

If on normal motorway journeys your car sits at 2 blobs (or 60ish degrees), then only sitting in traffic for a long period of time only takes it to 3 blobs (80-85 deg) this will be one of 2 things:

• Thermostat sticking open
• Faulty temperature sender

We have a guide on here to allow you to change the thermostat,  and the temperature sender is located on top of the thermostat. If you change the thermostat, you will get a new sender with it.

If you find your car is overheating, this can be one of a few things to look for:

• Thermostat sticking closed
• Airlock
• Faulty temperature sender
• Faulty water pump
• Head gasket failure
• Alternator belt failure

We have a guide for replacing the thermostat on here, and it will come with a new sender.

A simple airlock can really affect the temperature.  If you have recently bled the system and/or changed the coolant, this could be the problem. Follow our coolant change guide to re-bleed the system. 

A water pump failure can cause a lot of serious damage.  It is located at the front of the engine and driven from the alternator belt.  After checking that the belt is all still in place, you will need to lower the engine to give better access for changing the pump.

In some circumstances a head gasket failure can cause the hot gases to be pushed into the water cooling channels.  You will probably see an oil residue in the water, possible a milky residue on the oil cap, and will more than likely cause the engine not to run properly.

This would be 'Safe mode', commonly referred to as 'limp home mode'.

It is accompanied by the trust/esp light remaining switched on.

Sometimes this can be cause by a glitch or a power spike.... for example, switching all the electrics on at the same time.

Try switching the car off and on again, or disconnecting the battery for 15 minutes... this will reset the variable parameters (your driving style) and start the car 'afresh'.

Failing that it could be due to too much turbo boost, caused by very cold temperatures, a poor remap, or adjustment of the wastegate arm.

Check for restrictions in the air flow, ensuring that the wastegate arm is not altered. If the issue is recurring you may wish to speak to your remap provider to try a different one.

If there are no lights on the dashboard and no error codes, but the car still feels sluggish, it can be one of a number of things, all easy to check and rectify:

• Intercooler pipe has popped off
• Wastegate arm as come loose
• Crankcase breather pipe split/popped off
• Cycle valve failure

To check the intercooler pipes, open the engine bay, and just pull on both pipes!  If you get any movement then the pipe has popped off, commonly either on the turbo, or the turbo pipe to the intercooler... rarely would it be the intercooler to throttlebody pipe.

The 'E' clip which secures the wastegate arm onto the wastegate pivot might as well be made of chocolate. They corrode very quickly, and the arm will drop off, meaning that the wastegate flaps open and all of the gasses bypass the turbo.  Push the arm back on and replace the e-clip, though temporary fixes can be made with paperclips/hair clips.

The crankcase breather has a valve to stop the charged air from going down into the crankcase, but if this pops off (from the throttle body) then the boost is vented to air, usually with a splash of oil too! Simply replace the pipe or reconnect and secure with a hose clip.

Cycle valve failure: this can be checked using a winstar/star which can manually operate the valve to check its functionality. Replacement of the valve is fairly easy to do by yourself though.

Blue smoke is indicative of burning oil.  Have you checked your oil level recently?

The cause of this could be:

• Blocked breather pipe
• Worn piston rings
• Worn valve guides
• Turbo seal/bearing failure

White smoke (steam!) is indicative of water entering the system.

If you have just returned to your car after a period of a couple of weeks for example, and the steam clears, this should not be a problem. Damp can form in the exhaust system and should soon clear after starting. Give the car a good run to rid all the water from the exhaust.

If you get the white smoke every time you start the car and it doesn't clear, you need to look at the possibility of:

• Head gasket failure
• Broken coolant channel
• Faulty/failed turbo cooling channel

Check to make sure your coolant levels are okay.

Head Gasket failure is the most likely of the above; you may also notice water mixing with your oil too, so check for a white emulsion under the oil cap.

If you have a broken coolant channel, then unfortunately you will need a new engine block, but this will be very difficult to diagnose without removing the cylinder head from the car first anyway.

If the turbo cooling has failed you are likely to find water entering through the inlet manifold - remove the intercooler pipes to check for traces of water. This would require a new turbo.

Black smoke indicatees that your car is running rich: it's over-fuelling. Alongside the black smoke you'll probably be experiencing terrible fuel economy.

The reasons for overfuelling could include:

• Over-zealous remap (some remaps deliberately over-fuel for more power)
• Air restriction/blockage
• Faulty IAT or MAP sensor
• Faulty/failed fuel pressure regulator

If you have recently had a remap, and are only just noticing the excessive smoke, then it might be advisable to try a different remap. Some remaps deliberately overfuel to create more power. This can cause more problems in the future as it tends to wash the oil film from the cylinder bores leading to compression loss and piston ring failure.

Probably the easiest job is to check the airbox for leaves/restrictions!  Restricting the airflow can lead to a mixture difference resulting in over-fuelling.

Faulty sensors can provide false readings and cause the ECU to over-fuel, but diagnostics on a star/winstar should be able to read these.

A faulty fuel pressure regulator could allow greater fuel pressure through the injectors during their duty cycle, again causing over-fuelling. The regulator is easy and cheap to change.

Hearing a knock when at slow speeds can indicate that the suspension bushes are wearing. These are only about £5 each; alternatively an entire wishbone assembly is only about £30.

It could also be:

• Top mount nut loose
• Ball joint failure
• Engine mount failure

If the top mount is loose, then re-tighten or replace - however these are done up very tight so I would investigate as to why it is loose in the first place.

On early cars the lower ball joints (through a quality failure) were susceptible to water penetration causing early problems. These are subject to a VOSA recall number R/2000/031. Ball joints can just fail through general use, and replacing is the only option.

If the engine mount is worn/failed the knocking will be more prominent under acceleration but you will still hear knocking when going over bumps.

9 flashes indicates that the key fob battery is low... there is a guide on here to assist you.

In slightly rare cases, if the indicators flash continuously or randomly (or the car fails to respond), it could also indicate that the key fob has just or is about to lose synchronisation with the car. Unfortunately you cannot stop this, just get your spare ready and prepare to go to a independent smart specialist or main dealer - someone with access to a STAR machine - to have the key re-synchronised.

This is a common problem caused by a faulty brake light switch. The switch is located under the car and is inadequately protected from the rain. Eventually this switch is likely to fail.

The failure of the switch will mean that you have no brake lights, the car will not engage a gear, and if you were in reverse when it failed, it will not come out of gear! The switch contains the signal to allow the car to move out of reverse.

There is a guide on here to allow you to buy and change this switch yourself.

The noise can be attributed to one of a couple of things:

• Snapped front coil spring
• ABS ring splash plate not located correctly

If you look at the spring (can be either the top or the bottom of the spring), you will see a broken or missing section, the car will also sit slightly down on one side. The only solution is to replace the front spring (change them both at the same time!). There is an internal recall (service order) at smart to deal with this very well known problem, it's code is SO38. Phone a dealership to see if you are eligible for a free replacement.

If the springs are both okay, and the noise is a little more 'tinny' it could be that the backing plate for the front hub is mis-aligned, which causes the brake disc to *just* touch the plate under turning. Remove the front wheel, and relocate the backing plate.

All smarts that are equipped with the service indicator will display when the next service is due. This can be viewed by double tapping the display button as follows:

• fortwo 450: Double press the button on top of the dash.
• Roadster: Double press the middle button on top of the dash.
• fortwo 451: Double press the button to the left of the dash.

By default, this will display the distance the car has to travel before the service is due. The type of service will be either an 'A' or 'B' indicated by 1 or 2 spanners respectively. When service time approaches, the electronics will indicate that a service is due by displaying the distance left to go when you start the car. This screen will then revert to your previous display mode (outside temperature / trip / total distance covered).

However, the smart must also be serviced every year. So, if the distance hasn't been reached, the service counter will switch to the number of days left until the service is due. This will then count down each day.

If a service hasn't been performed by the time the counter reaches 0, the countdown will continue into negative numbers, e.g.: '-10' = Ten days overdue for service.

In order to make this change you will need to visit your local smart dealer or a mechanic with a STAR machine. The car needs connecting to smart specific diagnostics in order to make this change.

All Pures can have external temperature activated. It requires activation through the Mercedes STAR machine which most independent dealers have. No TAN code is required so this activation can be done at weekends.