P0706 - OBD II Trouble Code

Auto Systems and Repair

Transmission Range Sensor Circuit Range/Performance

Our emissions expert has put together the following information about the P0706 fault code. We have also included diagnostic procedures you can take to your repair shop if the mechanic is having difficulty analyzing the code.

OBD II Fault Code

  • OBD II P0706

Fault Code Definition

  • Transmission Range Sensor Circuit Range/Performance
What does this mean?

The purpose of the automatic transmission is to match the engine's optimum power and torque characteristics to the driver's desired rate of acceleration and speed by auto-selecting different gear ratios or 'speeds' to power the wheels. The Transmission Range Sensor (also referred to as the PRNDL input and/or neutral safety switch) tells the transmission control module (TCM) and the powertrain control module (PCM) that the transmission is in park, reverse, neutral, drive, low, 2nd, 3rd etc.  It is attached directly to the manual valve of transmission, so when the shift lever is moved say from park to drive, the Transmission Range Sensor communicates this critical information to the above mentioned vehicle computer systems. 

Symptoms

  • Check Engine Light will illuminate
  • Vehicle may not shift properly
  • Vehicle may not go into gear
  • Decrease in fuel economy
  • In unusual cases, there are no adverse conditions noticed by the driver
  • In some cases, there may be performance problems

Common Problems That Trigger the P0706 Code

  • Defective Transmission Range Sensor (PRNDL input)
  • Defective Transmission Range Sensor (PRNDL input) wiring or connector
  • Defective Valve Body
  • Defective manual shift valve linkage
  • Dirty transmission fluid that restricts the hydraulic passages

Common Misdiagnoses

  • Engine Misfire problem
  • Driveline problem

Polluting Gases Expelled

  • HCs (Hydrocarbons): Unburned droplets of raw fuel that smell, affect breathing, and contribute to smog
  • CO (Carbon Monoxide): Partially burned fuel that is an odorless and deadly poisonous gas
  • NOX (Oxides of Nitrogen): One of the two ingredients that, when exposed to sunlight, cause smog

P0706 Diagnostic Theory for Shops and Technicians

When the code P0706 is set in the Powertrain Computer, it means that the Powertrain Computer or PCM is not seeing a clear, rational change in the data sent from the Transmission Range Sensor, especially after the vehicle is in motion. For example, say the vehicle is going 25 mph, as reported by the vehicle speed sensor, but the Range Sensor is reporting that the transmission is still in park. This is an irrational (or impossible) condition, that is, how could the vehicle be going 25 mph and be in park? 

When diagnosing a P0706 code, it is important to record the freeze frame information and then to duplicate the code setting conditions with a test drive at speeds around 15-35 mph. Start out from a dead stop and gently accelerate. Watch the scan data to see if the Range Sensor is reporting accurate information to the TCM and PCM. If the Range Sensor is giving erroneous information to the TCM/PCM, then you may have located a problem that could set the P0706 code. The next step is to start doing pinpoint tests i.e voltage drops and continuity tests of the Transmission Range Sensor.  I generally back probe the Range Sensor, so I bypass any of the harness wiring. This accomplishes 2 things, I'm isolating the sensor from the wring harness and checking the quality of the connector and it's connection.   And, ALWAYS check the condition of the fluid. Is it dirty, brown and burnt or is it that clear cranberry color?

 


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