Transmission Range Sensor Circuit High Input
The P0708 code indicates that the Powertrain Control Module (PCM) has detected a voltage signal from the transmission range sensor (TRS) that is higher than the expected range. The TRS, also known as the neutral safety switch or inhibitor switch, tells the PCM which gear position (Park, Reverse, Neutral, Drive, etc.) the transmission is in. A high input typically means the sensor circuit is reading a voltage above the normal operating range, often due to a short to power, a faulty sensor, or wiring issues. This can cause incorrect gear selection, starting problems, and transmission performance issues.
1. Symptoms You Will Notice
- Check Engine Light illuminated
- Transmission stuck in one gear or fails to shift
- Engine starts in any gear or won't start
- Incorrect gear display on dashboard
- Reduced fuel economy
2. Most Common Causes
- Faulty transmission range sensor
- Short to power in the sensor circuit
- Damaged wiring or connector
- Corroded terminals
- PCM malfunction (rare)
3. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect the transmission range sensor and wiring for damage, corrosion, or loose connections.
Step 3: Test the sensor's voltage and resistance using a multimeter; compare with manufacturer specifications.
Step 4: Check for shorts to power or ground in the sensor circuit.
Step 5: If all tests pass, suspect a PCM issue; perform a PCM reset or reprogram if necessary.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended. The transmission may not shift properly or could get stuck in a gear, leading to unsafe driving conditions or transmission damage.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for parts and labor, depending on the vehicle and whether the sensor or wiring needs replacement.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.