Is the red engine management warning light (EML) on?

This could mean a faulty lambda or oxygen sensor. If your vehicle has a running problem, from our workshop in Chatham in Medway we have the knowledge and capability to diagnose and test many different sensors.

Oxygen Sensor:

The exhaust gas oxygen sensor is also known as a lambda sensor sends an input to the ECU to help balance the fuel/air mixture delivered to the combustion chamber. The correct air/fuel ratio allows the catalyst to break down emissions effectively. The sensor outputs a voltage signal representing the amount of unburnt oxygen in the exhaust gas.

A perfectly balanced fuel/air mixture is 14.7 parts of air to 1 part of fuel. The sensor’s output voltage fluctuates back and forth from rich to lean. Some lambda sensors have a heating element to reduce warm up time, a heated sensor can reach 500 degrees in 8 seconds. This quick warm up reduces emissions improving fuel economy sooner.

Some sensors can be bench tested by applying heat and measuring current output, but this method calls for removing the sensor which takes time and hence money. The more efficient way of testing is to use a scanner. Auto Experts Medway’s technicians possess diagnostic scanners that are able to read live data speeding up the diagnosis and hence keeping repair cost down.

Cam and Crank Sensors:

These two sensors are generally engine position sensors. A camshaft sensor checks the position of the camshaft and the crankshaft monitors the position of the crankshaft. Both of these sensors send information to the ECU. The ECU then uses this information to regulate when the coil should send power to the spark plug to ignite the fuel.

Why not book your vehicle in to our workshop in Chatham in the centre of Medway and our technicians can diagnose and replace a faulty cam or crank sensor.

MAP or MAF Sensors:

The Mass Air Flow sensor measures the volume of air passing through the air intake duct. This information is sent to the ECU which enables the ECU to adjust the amount of fuel delivered through the fuel injectors.

Some vehicles use a Manifold Absolute Pressure (MAP) sensor instead of a MAF sensor. The MAP sensor measures manifold pressure and sends this information to the ECU. The ECU then calculates air mass using the engine speed and temperature information. As with the MAF sensor this calculation is used to control the amount of fuel to inject.

Throttle Position and Temperature Sensors:

The ECU also receives signals from both the Throttle Position Sensor and the Coolant Temperature Sensor. This information helps to provide the perfect fuel/air mix for efficient combustion.

In Summary:

You can now begin to see why it is not just a case of simply reading fault codes and replacing a sensor. All these sensors are linked through the ECU and one sensor can effect the running of another.

Auto Experts Medway in Chatham are close to both Rochester and Gillingham in the centre of Medway, we can diagnose and replace all types of sensors including camshaft, crankshaft, map, maf, knock and temperature thermistors.

The red or orange EML is there to warn you that the engine is not running efficiently. This could be costing you money by using too much fuel, it could also cause further unnecessary damage to parts like your vehicles catalytic convertor. If you have a running problem do not hesitate calls us and book your vehicle in for diagnosis and repair.  Auto Experts Medway’s technicians are capable of carrying out the necessary live data reading of an ECU to establish exactly what part is required.

Why Choose Auto Experts Medway?

We at Auto Experts Medway in Medway have established a superb reputation for high quality vehicle repair services, refer to our testimonials from our customers from Chatham, Gillingham and Rochester on our testimonial page.

Share this:
Share this:

Contact Form


With two bays we are one of the largest testing stations in Medway. Use our booking request form to book your MOT and one of our team will get back to you to confirm.




Replacement – Balancing – Punctures



Clutch – Drive Shafts – Fly Wheels – Gearboxes – Prop Shafts – Rear Axles – Wheel Bearings – CV Joints and Gaitors


Steering and Suspension

Ball Joints – Bushes – Coil Spring – Power Steering – Shock Absorbers – Steering Rack – Suspension Arms – Tracking



Complete Systems – Catalytic Converters – Downpipes – Silencer – Manifolds – Oxygen Sensors – Rear Box – Particle Filters – Emissions



Cam Shafts – Cambelts – Cylinder Head – Fan Belts – Cylinder Head Gasket – Oil Pumps – Timing Chain – Turbos – Valves



Airbags – Alternators – Batteries – Bulbs – Coils – Diagnostics – HT Leads – Safety Restraint Systems (SRS) – Sensors – Spark Plugs – Starter Motors -Warning Lights – Washers


Cooling Systems

Anti-Freeze – Pressure Caps – Expansion Bottle – Hoses – Temperature Sensors – Radiators – Thermostats – Water Pump



Anti-Lock Brakes – Brake Master Cylinder – Brake Callipers – Discs – Drums – Fluid – Hoses – Pads – Pipes – Servos – Shoes


Air Conditioning

Blowers – Heater – Heater Matrix – Re-gassing