P0854: Drive Switch Input Circuit Low
The P0854 code indicates that the Powertrain Control Module (PCM) has detected a low voltage condition in the drive switch input circuit. This circuit is part of the transmission range sensor (TRS) or neutral safety switch, which tells the PCM whether the transmission is in Park, Neutral, Drive, or Reverse. A low voltage signal suggests a short to ground, a faulty switch, or a wiring issue. This can prevent the engine from starting or cause incorrect transmission operation.
01. Most Common Causes
- Faulty transmission range sensor (TRS) or neutral safety switch
- Short to ground in the drive switch circuit wiring
- Corroded or damaged connector at the TRS
- Failed PCM (rare)
02. Symptoms You Will Notice
- Engine may not start or only starts in Neutral
- Transmission may not shift properly or stay in limp mode
- Check Engine Light illuminated
- Incorrect gear indication on dashboard
03. Step-by-Step Diagnosis
Step 1: Scan for additional codes and note freeze frame data.
Step 2: Visually inspect the TRS connector and wiring for damage, corrosion, or shorts.
Step 3: Test the drive switch circuit voltage with a multimeter; should be near battery voltage when in Drive.
Step 4: If voltage is low, disconnect the TRS and check for continuity to ground; if shorted, repair wiring.
Step 5: If wiring is OK, replace the transmission range sensor.
04. Commonly Affected Makes
05. 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, leading to a crash. Have it diagnosed immediately.
How much does it cost to fix?▼
Typically $50-$150 for diagnosis and replacement of the transmission range sensor, plus labor.