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DTC codes / P05xx · Vehicle speed, idle control and auxiliary inputs / P05D6

P05D6Driver Mode Select Switch B Circuit High

P05D6 indicates that the powertrain control module (PCM) has detected an abnormally high voltage on the signal circuit for Driver Mode Select Switch B, which is typically a momentary contact switch used to scroll through or select driving modes. The PCM expects the signal circuit to rest at a reference voltage and be pulled low when the switch is pressed; a high-voltage condition means the circuit is open, shorted to voltage, or the switch contacts are stuck open.

SystemPowertrain
Code typeGeneric (all makes)
SeverityLow
Fix difficultyIntermediate
AreaVehicle speed, idle control and auxiliary inputs

Symptoms you may notice

  • The driver mode selection button does not respond or fails to change driving modes when pressed
  • The instrument cluster displays a persistent warning message or the mode indicator remains on a default setting
  • The check engine light (malfunction indicator lamp) is illuminated
  • Other steering-wheel or dashboard buttons on the same switch pack may stop working
  • Often no symptoms besides the warning light, especially if the vehicle defaults to a normal driving mode
  • In some vehicles, the transmission may stay in a default shift pattern or the throttle response feels different

Common causes, most likely first

  1. Open circuit in the signal wire between the mode switch and the PCM, often due to a broken wire in the steering column or dashboard harness
  2. Faulty driver mode select switch B with stuck-open internal contacts
  3. Corroded or loose electrical connector at the switch or at the PCM
  4. Short to voltage on the signal circuit, which can be caused by chafed wiring rubbing against a power wire
  5. Failed clock spring (spiral cable) in the steering wheel, which carries the switch signal on many vehicles
  6. Water intrusion or contamination in the switch assembly causing high resistance
  7. Rarely, an internal PCM fault that misreads the signal voltage

How to diagnose and fix it

  1. Verify the code with a scan tool and check for any related codes in other modules before proceeding
  2. Inspect the driver mode select switch B and its connector for physical damage, corrosion, or loose pins
  3. Disconnect the switch and measure resistance across the switch terminals while pressing and releasing the button; compare to specifications
  4. Check the signal circuit for continuity from the switch connector to the PCM connector, looking for opens or high resistance
  5. Measure voltage on the signal circuit with the switch disconnected and the ignition on to check for a short to voltage
  6. If the circuit and switch test good, substitute a known-good switch or perform a wiggle test on the harness while monitoring the scan tool data
  7. Repair or replace the faulty wiring, connector, clock spring, or switch as needed, then clear the code and verify the mode selection works

Why Mode Switch Codes Mislead

  • A high-voltage code on a switch circuit often means the switch is open rather than shorted, so replacing the switch without checking the wiring can be a costly mistake.
  • The clock spring is a common failure point on steering-wheel-mounted switches, and a broken clock spring can set this code even though the switch itself is fine.
  • Some vehicles use a resistor ladder network for multiple mode switches, so a single bad switch or wire can affect several functions and set multiple codes.
  • The PCM may set this code only after a specific number of key cycles with the fault present, so a intermittent connection may not trigger it immediately.
  • After repairs, the code may need to be cleared and a drive cycle performed before the PCM will re-enable mode selection, which can make a correct repair seem ineffective at first.

Can I keep driving with P05D6?

The vehicle remains safe to drive because the default driving mode is typically a normal setting, but you should avoid relying on mode selection until the fault is repaired. If the check engine light is accompanied by reduced power or strange transmission behavior, have it diagnosed promptly.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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