Mercedes-Benz W203 (C-Class 2000–2007, including the S203 estate and CL203 coupe): common faults, maintenance guides and repair tips.
The tank has two halves, and fuel is moved from one side to the other by an equalising or transfer pump. If the transfer does not work, one side stays...
The most common cause is the pump's hardened O-rings in the fuel line connectors, along with the cover seals. The cover bolts can also work loose over...
The return lines are disconnected from the injectors and routed into separate containers, after which the engine is cranked or run briefly. The test i...
Yes. The most common cause is hardened O-rings (round sealing rings) on the ends of the fuel lines, which let air into the low-pressure side. Symptoms...
The most common causes are air getting into the fuel line and too large an injector return leak. Air gets in through hardened O-rings and connectors, ...
The car limits power when boost pressure deviates from the permitted range. The cause is usually the boost pressure sensor, the turbocharger actuator ...
Revs limited to about 3000 is the engine's limp mode: the control unit limits power when some measurement or the boost pressure does not match. The fa...
The EPC light indicates an engine power limitation. Stalling is usually caused by the fuel pressure in the injector rail being too low. The system shu...
Typical symptoms are uneven running, misfires and revs dropping. The chain can stretch or jump a tooth or more, which shifts the engine timing. Drivin...
Most often a faulty ignition coil, spark plugs or leads. Other causes are a leaking vacuum hose or breather hose, the fuel pump or a clogged fuel filt...
The most common cause is a faulty thermostat: if it opens too early, the temperature stays low, and if it sticks closed, the engine overheats. Normal ...
Common leak points are the water pump, the heater core, the thermostat housing, the auxiliary heater gasket and the heating coil of the windscreen was...
The auxiliary heater is on the side of the engine under the intake manifold above the starter motor, a small aluminium box with wiring. It is usually ...
The most common cause is the plastic lever of the flap motor, which has cracked or broken. The unit interprets the flap as stuck when it does not move...
The most common causes are a refrigerant leak (for example from the condenser, the core in front of the radiator), a fault in the compressor or its el...
The oil must be approved for the transmission, not just any ATF. The 722.6 takes oil rated MB 236.10 or 236.14, the 722.9 transmission only 236.14. Ch...
P1856 means the selector lever position detection is not working. The car usually stays in one gear, for example second, and the gear display is blank...
Common causes are an old conductor plate, the TCC solenoid (the valve that controls torque converter lock-up) and a leaking bushing at the bulkhead co...
The cause is often the transmission conductor plate, which carries the speed sensor signals. Typical fault codes are P220A (sensor comparison not plau...
On a diesel the most common cause is a faulty electric auxiliary heater, located on the side of the engine under the intake manifold, which can draw a...
Measure the voltage at the battery terminals with the engine running. Normally the voltage is about 14 V. If it is about 11-12 V or does not rise afte...
One common cause is the fibre optic inside the ignition switch, which collects dust and moisture. The dirt blocks the infrared signal, and the fault g...
The cause is often the light switch connector: it is oxidised or its conductor pin has broken. Then the light functions and the side mirror adjustment...
The message means that the connection between the light and rain sensor and the roof light module is broken. The usual cause is the module's circuit b...
The lights usually come on when a sensor or the pump in the system reports an error. Common causes are worn brushes in the ABS/ESP pump motor, poor co...
The steering angle sensor has to be relearned. Start the car and turn the steering wheel from lock to lock a couple of times. If there is no fault, th...
The adjustment hatch is under the rear seat cushion. 1. Loosen the cables. 2. Adjust the shoes close through the bolt hole. 3. Tighten the cables from...
The most common causes are the anti-roll bar's body bushes and the bar's connecting rods, also called drop links, which wear and loosen. Next, check t...
The most common causes are loose lower or upper mounts and bushes of the rear shock absorber, the anti-roll bar's frame bushes and the front bushes of...
Common causes are battery or alternator undervoltage, a fault in the seat sensor mat or its wiring, a poor connector and interference on the CAN bus (...
The washer button must be pressed all the way down, otherwise the wipers just move. Other causes are a blocked pump inlet or washer nozzles, a seized ...