Auto Shift Manual Control Circuit Range/Performance
Diagnostic trouble code P0951 indicates that the powertrain control module (PCM) or transmission control module (TCM) has detected an out-of-range or performance issue in the auto shift manual (ASM) control circuit. This means the voltage or resistance signals from the manual shift control switch (such as paddle shifters or tap-shift buttons) do not match the expected values for a given state.
While this code typically will not strand you, it disables the manual shifting feature of the automatic transmission. It should be diagnosed soon to restore full transmission functionality and prevent potential erratic shifting.
Common symptoms
- Check Engine Light illuminated
- Inability to use manual shift mode (paddle shifters or tap-shift)
- Transmission defaults to standard automatic mode
- Erratic or harsh shifting when attempting to use manual mode
- Gear indicator on the dashboard may flash or display incorrectly
Likely causes
- Faulty auto shift manual control switch (paddle shifter or gear selector switch)
- Corroded, damaged, or loose wiring and connectors in the ASM circuit
- Spilled liquid or debris inside the center console affecting the shifter assembly
- Open or short circuit in the auto shift manual control wiring
- Faulty Transmission Control Module (TCM) or Powertrain Control Module (PCM) (rare)
What to check before replacing parts
Scan for all DTCs and record freeze frame data.
Look for: Check if other transmission or communication codes are present, which might indicate a broader electrical issue or module failure.
Visually inspect the wiring and connectors near the gear selector and steering wheel (if equipped with paddle shifters).
Look for: Look for chafed wires, disconnected plugs, or signs of liquid intrusion (like spilled coffee) in the center console area.
Monitor the auto shift manual switch PIDs using a scan tool while operating the switches.
Look for: The scan tool should show the switch state changing (e.g., upshift/downshift) when pressed. If the state does not change or fluctuates erratically, the switch or circuit is faulty.
Test the auto shift manual control switch for proper resistance or continuity using a multimeter.
Look for: Compare the resistance values in each switch position to the manufacturer's specifications. Out-of-spec readings indicate a failed switch.
Check the circuit wiring for continuity and shorts to ground or power between the switch and the TCM/PCM.
Look for: High resistance, an open circuit, or a short to ground/voltage indicates a wiring harness failure that needs repair.
This page explains the generic P0951 definition and is general reference information, not a diagnosis for your specific vehicle. Actual causes, severity, and repairs vary by make, model, engine, and mileage — always confirm with a scan tool and a qualified technician before replacing parts.
Gear guide: Best OBD2 ScannersRead this code yourself next time — from $20 Bluetooth dongles to bidirectional scan tools.Rather have a pro handle it? Find a vetted local mechanic.