Transmission Park Position Sensor Circuit Low
The P07B9 code indicates that the transmission control module (TCM) has detected a low voltage condition in the park position sensor circuit. This sensor tells the TCM when the transmission is in Park, enabling the engine to start and the key to be removed. A low circuit voltage can be caused by a faulty sensor, damaged wiring, poor electrical connections, or a malfunctioning TCM. This issue may prevent the vehicle from starting or cause incorrect gear position readings.
1. Symptoms You Will Notice
- Engine may not start or start only in Neutral
- Transmission stuck in Park or unable to shift out of Park
- Check Engine Light illuminated
- Incorrect gear position display on dashboard
2. Most Common Causes
- Short to ground in the Park B position sensor signal circuit
- Short to ground or voltage drop in the sensor power or reference circuit
- Faulty, demagnetized, or internally worn Park B position sensor
- Corroded, moisture-damaged, or bent/pushed-back pins in the sensor connector or harness
- Open circuit or excessive resistance in the wiring causing abnormal voltage drop
- Internal PCM/TCM failure in the sensor monitoring circuit
- Poor reference voltage source or shared dirty ground for transmission sensors
3. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm the code and check for other related codes.
Step 2: Visually inspect the park position sensor and its wiring for damage, corrosion, or loose connections.
Step 3: Test the sensor's voltage and ground signals using a multimeter; compare with manufacturer specifications.
Step 4: If sensor and wiring are okay, test the TCM for proper operation or update its software.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
No, it is not safe. The vehicle may not start or could shift unexpectedly, posing a safety risk. Have it diagnosed and repaired promptly.
How much does it cost to fix?▼
Repair costs typically range from $50 to $150 for sensor replacement or wiring repair, but could be higher if the TCM needs replacement.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.