Engine and Transmission

Delphi Ammonia Sensor

The Delphi Ammonia Sensor uses a unique Delphi technology to directly measure ammonia levels in the exhaust of diesel vehicles equipped with a selective catalytic reduction (SCR) aftertreatment system. The sensor output can be used to provide feedback to the SCR system helping provide optimal reduction of NOx emissions.

In a diesel engine SCR system, the ammonia sensor is typically situated either mid-brick or behind the SCR catalyst. The SCR system helps reduce NOx emissions in diesel powertrain systems through a chemical reaction in which ammonia reacts with NOx to produce nitrogen and water. Ammonia is typically introduced into the exhaust flow upstream from the SCR in the form of liquid urea. The ammonia sensor detects excess ammonia in the exhaust gas allowing for more precise dosing of urea. This added precision allows for optimal SCR system efficiency and prevents the release of excess ammonia into the atmosphere.

The Delphi Ammonia Sensor can detect ammonia within a range of 0 to 100 ppm. If the sensor detects too much ammonia, it signals the system to reduce the amount of the urea injection. The planar alumina substrate in the Delphi Ammonia Sensor combines an integral temperature sensor with a thick-film heater for optimum performance. The Delphi Ammonia Sensor provides measurement of ammonia without interference from carbon monoxide and NOx.


  • Provides optimized performance of an SCR converter
  • Enables the use of an optimally-sized SCR converter
  • Helps provide SCR system diagnostics
  • Enables optimal aftertreatment architecture
  • System includes Delphi-supplied sensor and sensor control module

Typical Applications

The Delphi Ammonia Sensor is intended for use in vehicles equipped with an SCR converter system including light duty, medium duty and heavy duty diesel vehicles to help manufacturers meet increasingly stringent NOx emissions regulations.


The Delphi Ammonia Sensor is in production. Engineering samples are available to current transportation industry customers upon request. Contact Delphi for further information.

Performance Advantages

The Delphi Ammonia Sensor helps the SCR converter operate at high efficiencies allowing for the most cost-effective means of meeting stringent NOx emissions regulations. The sensor provides required diagnostic feedback for urea quality/tampering and for proper operation of the aftertreatment system.

Exhaust sensors are increasingly important elements in today's engine management systems, helping to provide accurate engine control and system diagnostics. Delphi offers a wide range of exhaust sensors to help vehicle manufacturers meet current and future emissions regulations.

The Delphi Advantage

Delphi has one of the industry's most complete portfolios of sensors and a thorough understanding of systems integration. Delphi offers global manufacturing capabilities for sensors and the benefits of more than 30 years' experience in powertrain sensors research and production. Delphi has produced hundreds of millions of exhaust sensors and can provide manufacturers with the necessary support and high quality, high value products tailored to specific customer requirements.

As a global leader in engine management systems technology, Delphi can help manufacturers around the world meet emissions requirements, improve fuel economy and enhance performance. Delphi is a source for high value solutions and our systems expertise is built into every product. Delphi's flexible engineering approach encourages collaboration. And, Delphi has a thorough understanding of automotive markets around the world and a global network of resources.