Do Diesel Engines Have Lambda Sensors?

Lambda sensors were first developed in 1977 to help automotive engines run more efficiently. They are installed in both gasoline and diesel automobiles and help to minimize harmful emissions, mostly gases like carbon monoxide and pollutants, produced by your vehicle.

The sensors are made to perform in accordance with government exhaust gas regulations. They are also known as oxygen sensors or O2 sensors because of the role they play in the running of your car.

What does an O2 sensor do in a diesel?

The oxygen sensor is one of the most significant sensors in modern autos. The oxygen sensor, often known as the O2 sensor because O2 is the molecular formula for oxygen, measures the amount of unburned oxygen in the exhaust as it exits the engine. The sensor provides a technique of measuring fuel mixture by detecting oxygen levels. The O2 sensor tells the computer if the fuel mixture is burning rich (too much oxygen) or lean (too little oxygen) (too much oxygen). Knowing the fuel-to-air ratio allows your car’s engine to make any required adjustments to guarantee that it operates properly.

Since 1981, all cars have been required to have oxygen sensors. Many contemporary cars include numerous O2 sensors as a result of the ODB-II requirements, which apply to cars made from 1996. In fact, some automobiles have up to four oxygen sensors. A second oxygen sensor must be installed underneath the catalytic converter in cars manufactured after 1996. The operational efficiency of the catalytic converter is monitored by this O2 sensor.

It’s a symptom that the catalytic converter isn’t working effectively if the sensor following the catalytic converter shows modest variations from the reading on the first oxygen sensor. Modern V-6 and V-8 engines may feature up to four oxygen sensors, one in each cylinder bank and one after each catalytic converter. Your vehicle could have major engine problems if either the oxygen sensor in the cylinder block or the one for the catalytic converter fails.

Because oxygen sensors are so important to your engine’s performance and emissions control, you might be wondering when to replace them.

Is a lambda sensor the same as an oxygen sensor?

The lambda sensor, also known as an oxygen sensor, is a tiny probe situated between the exhaust manifold and the catalytic converter on the automotive exhaust.

What do diesels have instead of throttle bodies?

The lack of a throttle body in diesel engines is traditionally a key distinction between gasoline and diesel engines, though this is no longer true for all current diesels. In a diesel, pressing the accelerator pedal just instructs the fuel injectors to inject more diesel. More fuel injected implies more power, which means more exhaust, more air from the turbo, and the power output keeps rising.

Some diesel engines include throttle controls that allow for more precise adjustment of the intake manifold pressure, which aids in increasing the quantity of exhaust gas recirculation. Adding a throttle valve to the engine also aids in shutting it down by allowing you to taper the quantity of air allowed in for a smoother drop in RPM.

A throttle body, on the other hand, is required for gasoline engines. You’re merely opening up the throttle and allowing more air to flow into the engine when you press the (inappropriately titled) gas pedal. More air means more fuel is delivered by the injectors, and more fuel means more power.

Do diesels have fuel trims?

Diesels don’t do “Fuel Trim” in the traditional sense. The amount of air permitted into a gasoline engine is the primary “control”; fuel is then metered (“trimmed”) into the engine to match the amount of incoming air. A diesel engine works in the other direction.

What is lambda in diesel engines?

Oxygen probes, commonly known as lambda sensors, monitor the amount of oxygen in vehicle exhaust fumes. In relation to the stoichiometric air-fuel ratio, the air-fuel ratio, or lambda number (), specifies the mass ratio of air and fuel in the combustion chamber. When 0=1, perfect combustion conditions produce neither oxygen deficiency nor excess. A result of 1 suggests that there is too much air in the system (lean mixture). In spark ignition engines, the conventional lambda closed-loop control delivers a stoichiometric air-fuel combination for combustion. The method enriches the exhaust gases in a proportion that allows three-way catalytic converters to process them efficiently. Over a large load range, diesel engines or gasoline engines with direct injection run with a lean combustion, with the nitrogen oxide (NOx) content of emissions steeply increasing in tandem with the growing combustion temperature. Exhaust gas recirculation lowers the combustion temperature while also lowering the NOx content of released exhaust gases. The NOx storage catalytic converter can store residual NOx in the exhaust gas stream until it can be converted to nitrogen during rich combustion phases. For both exhaust recirculation and catalytic exhaust gas scrubbing, the lambda number represents the setpoint control value. The lambda number can be used as a starting point for determining the smoke limit at full load on diesel engines.

Do diesel engines need oxygen?

This means that for complete burning of diesel fuel, less air is required. When the air mass flow remains constant, as it was in these tests, the extra oxygen is utilised to burn the diesel and increases combustion.

Are NOX and O2 sensors the same?

The oxygen sensors are all based on the Nernst Cell principle. The difference could simply be in the length of connection from the sensor to the control module, or it could be in the coding of the control module for the sensor.

Why do cars have 2 lambda sensors?

Each exhaust pipe on a new car sold in the United States must be equipped with a catalytic converter, which uses chemical reactions inside the converter to convert toxic exhaust fumes into less dangerous ones. Since the mid-1990s, OBD II (On-Board Diagnostics II) emissions systems have required that each catalytic converter have one oxygen sensor positioned upstream and one oxygen sensor mounted downstream. As a result, single-exhaust vehicles will be outfitted with two oxygen sensors from the factory, while dual-exhaust vehicles will have four sensors.

Two oxygen sensors per exhaust pipe allow the engine control computer of a vehicle to compare the cleanliness of the exhaust before it enters the catalytic converter to the exhaust after it departs. This not only provides the legally needed self-check to monitor if one of the sensors fails, but it also allows the catalytic converter’s efficiency to be monitored.

The vehicle’s engine control unit (ECU) can use this information to compensate for the rich air-fuel mixes that are a natural byproduct of cold engine starts. During engine warming, some vehicles have used a supplementary air pump to load the exhaust system with extra oxygen from outside air, assuring clean overall emissions. The most recent solution to this problem does away with the air pump and instead relies on the ECU to change the fuel-air ratio between lean and rich until the engine reaches operating temperature.

Excess unburned hydrocarbons traveling through the exhaust system will foul oxygen sensors and catalytic converters over time, reducing their lifespan and costing the consumer a significant repair bill.

Narrow Band (Standard) vs. Wide Band Oxygen Sensors

When searching through our inventory of replacement oxygen sensors, you’ll find that some are labeled as “Large band.” This stands in contrast to “For decades, “narrow band” sensors have been standard OEM factory equipment. Wideband oxygen sensors are designed to read a considerably wider range of fuel-to-air ratios, allowing them to determine how much unburned fuel is present in the exhaust system. If you’re calibrating for higher power, this information will come in handy. We have wideband oxygen sensors from

Both Bosch and


If you’re not sure which type of sensor you need, put your car’s year, make, and model into our website, and it will direct you to sensors that are particular to your vehicle.