P0855 - Drive Switch Input Circuit High
The P0855 code indicates that the Powertrain Control Module (PCM) has detected a high voltage signal from the drive switch circuit, which is typically used to detect when the vehicle is in gear (e.g., Drive or Reverse). This circuit is part of the transmission range sensor or neutral safety switch. A high voltage condition can be caused by a short to power, a faulty switch, or a wiring issue. This can affect transmission operation and may prevent the engine from starting or cause erratic shifting.
01. Most Common Causes
- Faulty drive switch (transmission range sensor)
- Short to power in the drive switch circuit wiring
- Corroded or damaged connector at the switch or PCM
- Failed PCM (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Engine may not start or start only in Park/Neutral
- Transmission may not shift properly or stay in limp mode
- Incorrect gear indication on the dashboard
03. Step-by-Step Diagnosis
Step 1: Use a scan tool to confirm the code and check for related codes.
Step 2: Inspect the drive switch connector and wiring for damage, corrosion, or shorts to power.
Step 3: Test the drive switch signal voltage with a multimeter; compare to manufacturer specifications.
Step 4: If wiring and switch are okay, test the PCM for proper operation (may require professional diagnosis).
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended. The vehicle may not start or may shift erratically, posing a safety risk. Have it diagnosed promptly.
How much does it cost to fix?▼
Typically $50-$150 for diagnosis and repair, but costs can vary depending on the exact cause and labor rates.