The OBDII error code P0706 indicates a problem with the Transmission Range Sensor (TRS), also known as the neutral safety switch or park/neutral switch. This sensor plays a vital role in your vehicle’s operation, communicating the gear shifter’s position to the Powertrain Control Module (PCM). A malfunctioning TRS can lead to drivability issues and safety concerns. This article will delve into the causes, symptoms, and diagnostic procedures associated with the P0706 code.
Example of an external Transmission Range Sensor (TRS)
What Does the P0706 Code Mean?
The P0706 code signifies a range/performance issue within the TRS “A” circuit. The PCM receives varying voltage signals from the TRS corresponding to each gear position (Park, Reverse, Neutral, Drive). When the voltage signal doesn’t match the expected value for the selected gear, the P0706 code is triggered. This is a “C” type DTC, meaning it’s non-emission related and might not illuminate the check engine light or store freeze frame data. However, it can significantly impact your vehicle’s performance and safety.
Symptoms of a P0706 Code
A faulty TRS can manifest in several ways:
- Starting in Any Gear: The vehicle might start even when the shifter isn’t in Park or Neutral, posing a serious safety hazard.
- Limp Mode: The PCM might force the transmission into “limp mode” to prevent further damage. This results in reduced power and limited gear selection. You’ll likely notice a significant lack of acceleration, especially from a standstill.
- Erratic Shifting: The transmission might shift erratically or refuse to shift altogether.
Common Causes of a P0706 Code
Several factors can contribute to a P0706 code:
- Faulty Transmission Range Sensor: The TRS itself might be defective due to wear and tear, internal damage, or corrosion.
- Misadjusted Transmission Range Sensor: An incorrectly adjusted TRS can send inaccurate signals to the PCM.
- Wiring Harness Issues: Damaged, corroded, or shorted wiring in the TRS harness can disrupt communication between the sensor and the PCM. This is often seen in four-wheel-drive vehicles that have experienced off-road damage.
- Faulty PCM (Rare): In rare cases, a malfunctioning PCM can be the root cause, though this is less likely than other issues.
Diagnosing and Repairing a P0706 Code
Diagnosing a P0706 code involves a systematic approach:
- Visual Inspection: Begin by thoroughly inspecting the TRS and its wiring harness for any visible damage, corrosion, or loose connections. Always engage the parking brake before performing any inspection.
- Starting Test: Check if the vehicle starts in gear other than Park or Neutral. If it does, disconnect the TRS and try again. If the vehicle still starts in gear with the TRS disconnected, suspect a short in the wiring harness. If it doesn’t start, the TRS itself is likely faulty or misadjusted.
- Voltage Test: Use a multimeter to test the voltage at the TRS connector. Compare the readings with the manufacturer’s specifications to determine if the sensor is sending the correct signals.
- Harness Inspection: If the voltage test indicates a problem, thoroughly inspect the wiring harness for any breaks, shorts, or damage.
- TRS Replacement/Adjustment: If the TRS is determined to be faulty, replace it with a new one. If misadjusted, follow the manufacturer’s instructions for proper adjustment.
- PCM Check (Last Resort): If all other components check out, a faulty PCM might be the culprit. However, this is a rare occurrence and should only be considered after exhausting all other possibilities.
Conclusion
The EOBD/OBDII error code P0706 indicates a problem with the Transmission Range Sensor circuit. Addressing this issue promptly is crucial to ensure both the drivability and safety of your vehicle. While a DIY approach is possible for experienced individuals, consulting a qualified mechanic is recommended for accurate diagnosis and repair, especially if the problem involves complex wiring or potential PCM issues. Ignoring this code can lead to more serious and costly repairs down the line. Remember to always consult your vehicle’s specific repair manual for detailed instructions and safety precautions.
