The Functionality of the Analog Transmission Range Sensor and How to Diagnose Issues

October 22, 2020 Cadence PCB Solutions

Key Takeaways

  • Learn about all the systems affected by the Analog Transmission Range Sensor.

  • Gain a greater understanding of the functionality of the Analog Transmission Range Sensor.

  • Learn how to diagnose the common issues associated with the Analog Transmission Range Sensor.

 Analog Transmission Range Sensor affects vehicle functionality.

Outside the world of simulation, an electronic device, system, or circuit must interact with other devices or systems to function. This interaction typically involves some form of communication, which requires an intermediary.

Communication involves reading input signals, from an ON or OFF switch, for instance, which makes devices like sensors ideal for the task. Furthermore, an electronic system or circuit cannot function or perform its task without this ability to communicate.

Sensors and Transducers

The functional ability of all electronic devices falls under this same premise, regardless of industry or field. This, of course, heightens the critical nature of sensors in the field of electronics. However, there is another device of equal importance to device or circuit functionality, and it is called a transducer.

A transducer is a combination of two types of sensors. The first type of sensor is those capable of sensing vast arrays of energy forms, i.e., magnetic energy, electrical signals, and movement, to name a few. The second type of sensor is called an actuator, which can be used to switch both currents and voltages.

Overall, there are various types of transducers and sensors in the field of electronics. This includes analog and digital versions that are available as input (sensor or transducer) or output (sensor or transducer). The type of transducer (input or output) one uses is dependent on the nature of the signal it is sensing or the process it is controlling. Functionally, a transducer or sensor is a device that provides the conversion of a physical quantity into another physical quantity.

Sensor Classifications and Types

In summary, sensors detect changes in electrical or physical quantities and generate an optical or electrical output that corresponds to this change in a specific quantity. Sensors observe the changes that occur in the physical world and relay a type of feedback to microprocessors or microcontrollers. To achieve sensor functionality, we must provide adequate grounding and supply power (excitation).

There are two general types of sensors:

  • Analog Sensors

  • Digital Sensors

Analog Sensors

Different types of sensors produce continuous analog output signals, and these sensors are called analog sensors. Analog sensors have a constant output that is proportionate to the quantity intended to be measured. Overall, there are numerous types of analog sensors, including temperature sensors, light sensors, accelerometers, sound sensors, and pressure sensors, to name a few.

Analog sensors observe or sense physical or external parameters and provide an output as an analog voltage. These parameters include light intensity, solar radiation, gear position, or even wind speed. However, when we examine the output of an analog sensor, we can observe its range, i.e., from 0 volts to 5 volts. A value ranging from 3.5 volts to 5 volts is considered a Logic High or 1, while a value ranging from 0 volts to 3.5 volts is a Logic Low or 0.

Digital Sensors

A digital sensor generates discrete values, i.e., 1(s) and 0(s). We refer to these discrete values as binary or digital signals, and they are prominent in digital communication.

Some examples of digital sensors include electrochemical sensors and electronic sensors.

The Analog Transmission Range Sensor

The field of computers now expands far beyond the confines of the workplace or home office. The advancements in the automotive industry include AI that performs tasks that were once only possible with the human element, i.e., driving. These advancements did not happen overnight, but rather gradually, system by system. However, today’s vehicles are as dependent on technology as they are on the fuel source they use.

Sensors in the automotive industry, by any metric, are indispensable to overall vehicle functionality. The Analog Transmission Range Sensor is an excellent example, as it is a part of the TCM (transmission control module) and used in late-model vehicles. In terms of construction, an Analog Transmission Range Sensor consists of a series of resistors that decrease the voltage signal returned to the PCM (power control module) per the shift lever position.

Note: The TCM is similar to a miniaturized computer system, and it interprets the component’s electrical sensor outputs in the engine (automatic transmission). However, the PCM is a control unit, and it is a combination of the engine and transmission control units. Overall, the PCM is a critical component since it affects more than 100 processes within a vehicle.

The Functionality of the Analog Transmission Range Sensor

The Analog Transmission Range Sensor (transmission position sensor) or TR Sensor, is vital to overall vehicle functionality. It is also an electronic sensor that gives positional input data to the PCM (powertrain control module), which affords the PCM control of the transmission per the position commands of the sensor.

This is important, as the starter will not crank unless the transmission is in the park or neutral position. As you might imagine, if the Analog Transmission Range Sensor provides an inaccurate gear position, the result will be detrimental to vehicle functionality. Keeping this in mind, like all devices and components, the TR Sensor will fail over time or even wear out. As stated, if the Analog Transmission Range Sensor fails or succumbs to any type of malfunction, several possible symptoms could appear:

  • The vehicle will not start or is unable to move

This is because, without the correct position input data from the TR Sensor (i.e., Park or Neutral), the PCM will be unable to crank the engine. Also, if the vehicle suffers a complete Analog Transmission Range Sensor failure, the PCM will be unable to see any gear position command. This, in turn, will render the vehicle immobile.

  • The transmission will go into a different gear position than the one chosen

This, of course, results in the transmission appearing, for example, to be in Drive, when it is actually in Reverse. The unsynchronized PCM input can lead to an unsafe condition, i.e., a road hazard.

  • The vehicle will enter into what is called a limp mode

In some instances, when the Analog Transmission Range Sensor fails, it is possible for the transmission to still be mechanically in gear. However, the PCM will be unable to see or know which gear. At this time, the transmission locks into one particular gear for safety, and this scenario is called Limp Mode. Moreover, depending on the vehicle manufacturer and transmission type, the limp mode can be 5th, 4th, or 3rd gear, and even Reverse.

However, since the Analog Transmission Range Sensor utilizes resistance for its functionality, you can use an ohmmeter to help diagnose the issue if there is no scan tool available. If you are using an ohmmeter, measure the resistance at various gear positions and compare those readings to the manufacturer’s listed specifications.

The Analog Transmission Range Sensor is critical to vehicle functionality and mobility. Regardless of vehicle type, the Analog Transmission Range Sensor is like a vehicle’s Achilles heel.

Whether you are utilizing a single-sided board or a multi-layer design, you will need the right set of PCB layout and design software. Allegro PCB Designer and Cadence's full suite of design tools can help you create designs from verified component models and analyze all aspects of its functionality. You will also have access to a set of tools for MCAD design and preparing for manufacturing.

If you're looking to learn more about how Cadence has the solution for you, talk to us and our team of experts.

 

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