When issues arise with a vehicle's automatic transmission, a diagnostic trouble code (DTC) often "pops up" and illuminates the check engine light on the dashboard. These codes help identify the specific area or component experiencing a malfunction.
The transmission control module (TCM) or powertrain control module (PCM) stores these codes, which can then be retrieved using an OBD-II scanner. Understanding these codes is the first step in diagnosing and addressing transmission problems.
Common Transmission Diagnostic Trouble Codes
Several specific codes indicate common issues related to the transmission system. Here are some diagnostic trouble codes that can appear for transmission-related problems:
| Trouble Code | Description |
|---|---|
| P0704 | Clutch Switch Input Circuit Malfunction |
| P0705 | Transmission Range Sensor Circuit Malfunction (PRNDL Input) |
| P0706 | Transmission Range Sensor Circuit Range/Performance |
| P0707 | Transmission Range Sensor Circuit Low Input |
Understanding These Codes
These codes generally point to issues with sensors or switches vital for the transmission's proper operation:
- P0704 indicates a problem with the clutch switch input circuit. In vehicles with an automatic transmission, this might relate to the park/neutral position switch or an equivalent input that tells the system if the vehicle is in a state to start or engage gears.
- P0705, P0706, and P0707 all pertain to the Transmission Range Sensor (TRS), often referred to as the PRNDL switch. This sensor communicates the shifter's position (Park, Reverse, Neutral, Drive, Low gears) to the vehicle's computer.
- P0705 signals a general malfunction in this sensor's circuit, meaning the input from the sensor is incorrect or missing.
- P0706 suggests that the sensor's reading is outside the expected range or its performance is inconsistent. For example, it might indicate the vehicle is in two gears at once, which is impossible, or that the signal doesn't correspond to a valid gear selection.
- P0707 indicates a low voltage input from the TRS circuit, which could mean a wiring issue, a faulty sensor, or an electrical short.
What to Do When a Transmission Code Appears
If your vehicle displays one of these transmission codes, it is advisable to:
- Use an OBD-II Scanner: Confirm the specific code(s) that are present.
- Research the Code: Understand what the code means for your specific vehicle make and model, as definitions can sometimes have slight variations or common causes.
- Check for Symptoms: Note any accompanying symptoms such as rough shifting, inability to shift, or the vehicle going into "limp mode" (reduced power and limited gears).
- Consult a Professional: While some issues might be simple, transmission problems can be complex and often require professional diagnosis and repair. Ignoring these codes can lead to more severe and costly damage to your transmission system.
For more detailed information on specific diagnostic procedures and a broader range of transmission trouble codes, resources like StreetSmart Transmission offer extensive guides.
