Sensors

• It measures the position of the throttle valve when you press the accelerator pedal
• The sensor sends the information to the ECU, which then decides how much air-fuel mixture needs to be sent to the cylinder
• A faulty throttle position sensor hampers the power delivery

• It is a sensor that monitors the engine load
• It calculates the difference between the manifold and outside pressure
• The MAP sensor ensures that the engine relieves fuel based on the change in pressure
• The failure of the MAP sensor may result in high fuel consumption

• A camshaft controls the inlet and exhaust valves of an engine
• The camshaft position sensor monitors the timing of the camshaft so that the air enters the cylinder and burnt gases are sent out of the cylinder at the right time
• If the timing is off, it hampers the power output, and in the worst case, it may damage the cylinder

• It is a sensor that monitors the speed and position of the crankshaft
• The sensor is fitted to the crankshaft
• It detects the crankshaft position and relays the information to the ECU
• The ECU then calculates the exact time for fuel injection and activate the spark plugs
• If timing is not correct, the engine loses its efficiency
• It is one of the most important sensors in a car

• Knocking is a phenomenon where the air-fuel mixture ignites before the spark plugs produce the spark
• It reduces engine efficiency, and in the longer run, it can cause damage to the engine components
• The engine knock sensor detects knocking by monitoring the air-fuel mixture ignition process
• The sensor can warn the driver if there is any fault in the ignition of the air-fuel mixture

• It is a type of sensor that measures the volume and density of air entering the engine
• It is placed inside the combustion chamber
• It ensures the right amount of air-fuel mixture enters the combustion chamber for optimum performance
• Failure of the air-flow sensor can result in engine stalling or more fuel consumption

What is an Exhaust gas temperature sensor?

An exhaust gas temperature sensor measures the temperature of the exhaust gas. This information is then relayed back to the engine control unit or ECU, where the appropriate action is taken. In petrol engines, its main role is to protect key components from the higher temperatures common with downsized engines - so if the sensor detects excessive temperatures, the ECU will reduce the temperature, by lowering boost pressure in the case of the turbocharger.

In diesel engines, exhaust gas temperature sensors are also used to monitor the temperature of the diesel particulate filter (DPF) to  establish the correct temperature for regeneration, reducing harmful emissions. It is not uncommon to have three or more sensors fitted to the exhaust; one prior to the turbocharger, one before the DPF and the third after the particulate filter

There are two types of exhaust gas temperature sensors; one with a positive temperature coefficient (PTC) sensing element, and the other negative temperature coefficient (NTC), the only difference being how they measure the temperature. The NTC element has a high resistance at low temperatures and a low resistance at high temperatures. Resistance decreases as the the temperature increases. The PTC element, the most common type resistance increases in line with temperature. Either way a temperature is assigned to the resistance in the ECU and action is taken accordingly.

Common causes of exhaust gas temperature sensor failure is exposure to excessively high temperatures - over 900°C in some cases, the very thing they protect other components from.

As with all wired sensors, severe vibrations can also loosen internal connections and any bends or twists can cause the wire to break, making them particularly vulnerable to damage when replacing other components in the exhaust system.

Alongside contamination from other fluids such as oil or antifreeze, these can all affect the sensor's response characteristics, causing it to drift out of tolerance and prove inaccurate readings.

Possible symptoms of a faulty Exhaust Gas Temperature Sensor:

1. Check the engine light
2. Reduced fuel efficiency
3. Unnecessary or no DPF Regeneration
4. Failed emissions test

When the DPF differential pressure sensor stops signalling the PCM to regenerate, the DPF can come completely obstructed by contaminates and fail.

Here are some Signs to look out for;

1. Engine Light
2. Poor fuel economy
3. Poor engine performance
4. High engine temperatures
5. High transmission temperatures
6. Rough or uneven idling

When the DPF fails, exhaust gases can not be fully purged as backpressure pushes exhaust back into the combustion chamber causing DPM or soot to mix in with the engine oil. If the engine check light is illuminated the vehicle will not perform a regeneration cycle. In extreme cases, the faulty sensor will trigger the ECU to default to a limp home mode with reduced performance. A DPF pressure sensor is vital to the longevity of the DPF, and if the DPF becomes completely obstructed, the regeneration process will not fix it. It will need to be removed and professionally cleaned or replaced.  

If your check engine light is turned on, here are some of the codes associated with a DPF pressure sensor electrical problems...

• P2452: Diesel Particulate Filter Pressure Sensor 'A' Circuit
• P2453: Diesel Particulate Filter Pressure Sensor 'A' Circuit Range/Performance
• P2454: Diesel Particulate Filter Pressure Sensor 'A' Circuit Low
• P2455: Diesel Particulate Filter Pressure Sensor 'A' Circuit Hi

Since the oxygen sensor is in the exhaust stream, it can become contaminated. Common sources of contamination include an excessively rich fuel mixture condition or oil blow-by in an older engine and engine coolant being burnt in the combustion chamber as a result of on engine gasket leak.

It is also exposed to extremely high temperatures, and like any component can wear over time. These can all affect the oxygen sensor's response characteristics, resulting in an extended response time or a shift in the sensor voltage curve and in the long run reduced sensor performance.

What to look out for in a failing 02 Sensor: 

1. Check engine light
2. Poor fuel economy
3. Rough engine idle or misfiring
4. Sluggish engine performance

Common Fault Codes:

• P0135: Oxygen sensor in front of the catalytic converter 1, heating circuit/open
• P0175: System too rich (bank 2)
• P0713: Fuel trim malfunction (bank 2)
• P0162: 02 Sensor Circuit malfunction (bank 2, sensor 3)