P0855 — Drive Switch Input Circuit High #

Note: The code description may vary depending on the vehicle manufacturer (OEM). Below are known description variants for this code:

• P0855 — Drive Switch Input Circuit High (Generic/SAE)
• P0855 — Drive Switch Input Circuit High Input (Chrysler, Ford, GM)
• P0855 — Gear Drive Switch Input Circuit High (Nissan, Toyota)
• P0855 — Transmission Drive Switch Input High (Hyundai, Kia)

Summary of DTC P0855 #

The P0855 diagnostic trouble code (DTC) indicates that the transmission control module (TCM) or powertrain control module (PCM) has detected a voltage that is too high in the Drive Switch Input Circuit. This circuit is used to monitor the status of the drive switch, which communicates the driver’s gear selection, especially in vehicles with automatic transmissions and certain 4WD systems. When the voltage exceeds the OEM-specified threshold, the module logs the P0855 code to alert of a possible electrical fault, wiring issue, or switch malfunction. This code is mainly associated with the transmission’s ability to recognize when the “Drive” position is selected. Addressing this code promptly helps ensure proper gear selection and prevents potential drivability or safety concerns.

Common Symptoms for P0855 #

When P0855 is stored, you might notice several symptoms—or sometimes none at all, depending on the severity and the vehicle’s fail-safe strategy. Typical symptoms include irregular shifting patterns, the transmission staying in a single gear (limp mode), or warning lights on the dashboard. In some cases, the vehicle may not engage “Drive” at all. If you’ve ever felt like your car is ignoring your command to move forward, this code could be the culprit.

• Check Engine Light (CEL) illuminated
• Transmission stuck in a single gear (limp mode)
• Inability to shift into Drive or out of Park
• Erratic or harsh shifting
• Transmission warning indicator or messages
• No observable symptoms (in rare cases)

Most Likely Causes of P0855 #

The underlying causes of a P0855 code are typically electrical in nature, often stemming from issues with the drive switch itself or the wiring harness connected to it. The following list ranks the most common causes by frequency. Remember, pinpointing the true source requires a methodical diagnostic approach.

1. Faulty drive range switch (sometimes known as the transmission range switch or PRNDL switch)
2. Open or short circuit in the drive switch input wiring
3. Poor electrical connection at the drive switch or its connector
4. Damaged, corroded, or loose connector pins
5. Failed transmission control module (TCM) or powertrain control module (PCM) (rare)
6. Aftermarket wiring modifications or previous repairs introducing faults

Step-by-step Diagnostic for P0855 #

Diagnosing a P0855 code doesn’t have to feel like searching for a needle in a haystack. By following these systematic steps, you can efficiently narrow down the root cause. Always refer to your vehicle’s factory service manual for specific procedures and safety precautions.

• 1. Verify the code: Use a scan tool to confirm the presence of P0855 and check for any related transmission or shift switch codes.
• 2. Visual inspection: Inspect the drive switch and its wiring harness for visible damage, corrosion, or loose connections.
• 3. Check connector integrity: Disconnect the drive switch connector; look for bent, pushed-out, or corroded pins.
• 4. Measure circuit voltage: With a digital multimeter, measure voltage at the drive switch circuit—compare it with OEM specifications.
• 5. Test switch operation: Use a scan tool or multimeter to monitor the drive switch input while shifting through gear positions. Verify if the signal changes as expected.
• 6. Check continuity: Perform continuity and short-to-power/ground tests on relevant wiring between the switch and the control module.
• 7. Inspect the TCM/PCM: If all wiring and switch tests pass, consider evaluating the TCM/PCM as a last step. Substitute with a known-good unit only if directed by OEM procedures.
• 8. Clear codes and road test: After repairs, clear the code and road test the vehicle to confirm the repair.

Possible Repairs for P0855 #

Once the root cause is pinpointed, repair options become much clearer. The appropriate fix depends on which component or connection is at fault. Below is a targeted list of repairs that address the most common causes of this code.

• Replace the faulty drive range/gear switch if defective.
• Repair or replace damaged wiring or connectors in the drive switch circuit.
• Clean or replace corroded connector terminals.
• Secure all loose connections at the switch and module ends.
• Reprogram or replace the TCM/PCM if diagnosed as faulty (rare and only after thorough diagnosis).
• Remove any unapproved aftermarket modifications affecting the circuit.

Is It Safe to Drive with Code P0855? #

Limited: Driving with a P0855 code is generally not recommended, especially if you experience shifting issues or the vehicle is stuck in limp mode. While some vehicles may still operate, the inability to properly select gears can compromise safety—particularly when merging onto highways or navigating traffic. In some cases, the car may not move at all or may unexpectedly change gears. It’s best to address the problem as soon as possible to avoid being stranded or causing further transmission damage.

Vehicles Most Commonly Affected by P0855 #

While P0855 is a generic OBD-II code, some makes and models are more commonly associated with it, often due to design or switch placement. The following vehicles are frequently reported with this code:

• Dodge, Chrysler, and Jeep (especially minivans and SUVs with electronic range selectors)
• Ford (F-150, Explorer, and certain sedans with electronic shift modules)
• Nissan (Pathfinder, Frontier, and Altima with electronic transmission range switches)
• Toyota and Lexus (4Runner, Tacoma, and SUVs with advanced shifter assemblies)
• Hyundai and Kia (Sorento, Santa Fe, and Sonata with electronic transmission controls)
• GM/Chevrolet (Silverado, Malibu, and SUVs with electronic gear selectors)

Common Mistakes & Best Practices for P0855 #

When troubleshooting a drive switch input circuit, it’s easy to overlook the basics or jump to conclusions. Avoiding these pitfalls can save you time, money, and frustration. Here are frequent mistakes and recommended best practices:

• Skipping the basics: Always perform a thorough visual inspection before replacing parts.
• Assuming the TCM/PCM is faulty too soon: Control modules rarely fail; exhaust all wiring and switch diagnostics first.
• Overlooking intermittent issues: Wiggle test the harness and observe for fluctuating voltages.
• Not verifying repairs: Always clear codes and confirm the fix with a road test before returning the vehicle to service.
• Using non-OEM parts: Whenever possible, use OEM components to ensure compatibility and reliability.

Quick FAQ for P0855 #

Here are some quick answers to common questions about the P0855 code:

• Q: Can a dead battery cause P0855?
  A: While a dead battery can cause a range of electrical issues, P0855 specifically relates to the drive switch input circuit and is unlikely to be triggered by battery failure alone.
• Q: Do I need to replace my transmission if I get P0855?
  A: No, this code is usually caused by an electrical issue in the drive switch circuit, not a mechanical failure in the transmission. Replacing the transmission is almost never required for this code.
• Q: Will my car fail an emissions test with P0855?
  A: P0855 is not directly related to emissions, but the presence of any active OBD-II code can result in a failed inspection until the issue is resolved and codes are cleared.