P0904: Gate Select Position Circuit Malfunction
The P0904 code indicates a fault in the gate select position circuit of an automated manual transmission (AMT) or dual-clutch transmission (DCT). This circuit monitors the position of the gear selector gate (e.g., Park, Reverse, Neutral, Drive). The powertrain control module (PCM) detects an electrical issue such as an open, short, or out-of-range signal from the gate select position sensor. This can prevent proper gear engagement and may cause transmission performance issues.
01. Most Common Causes
- Faulty gate select position sensor
- Damaged wiring or connector in the gate select circuit
- Corrosion or poor electrical connection
- Failed transmission control module (TCM)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Transmission stuck in one gear or fails to shift
- Erratic gear selection or inability to select gears
- Reduced fuel economy and performance
03. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm P0904 and check for other related codes.
Step 2: Visually inspect the gate select position sensor and its wiring harness for damage, corrosion, or loose connections.
Step 3: Test the sensor's voltage and resistance per manufacturer specifications using a multimeter.
Step 4: If sensor and wiring are okay, test the TCM for proper operation and communication.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended. The transmission may fail to shift properly, leading to unsafe driving conditions or transmission damage.
How much does it cost to fix?▼
Repair costs typically range from $150 to $400, depending on whether the sensor, wiring, or TCM needs replacement and labor rates.