Auto Shift Manual Mode Circuit Range/Performance
This code indicates that the transmission control module (TCM) or powertrain control module (PCM) has detected an erratic or out-of-range voltage signal from the auto shift manual mode circuit. The computer sets this code when the electrical values from the manual shift switches, such as paddle shifters or console up/down selectors, do not match expected performance parameters.
While the vehicle is generally safe to drive in standard automatic mode, the manual shifting feature will likely be disabled. It should be diagnosed soon to restore full transmission functionality and prevent potential wiring shorts.
Common symptoms
- Illuminated Check Engine Light
- Inability to use manual shift mode (Tiptronic/paddle shifters)
- Transmission defaults to standard automatic mode
- Gear indicator on the dashboard fails to update in manual mode
- Erratic or delayed shifting when attempting to manually change gears
Likely causes
- Faulty auto shift manual switch (shifter assembly or paddle shifters)
- Liquid spilled on the center console shifter area causing a short
- Damaged, corroded, or loose wiring and connectors in the shifter circuit
- Faulty steering wheel clockspring (if equipped with paddle shifters)
- Faulty Transmission Control Module (TCM) or Powertrain Control Module (PCM)
What to check before replacing parts
Inspect the center console and shifter assembly for signs of spilled liquids or physical damage.
Look for: Sticky residue, corrosion, or damaged wiring harnesses near the shifter mechanism.
Use a scan tool to monitor the Auto Shift Manual switch PID data while toggling the switches.
Look for: The scan tool should show the switch state changing from 'Off' to 'On' consistently; erratic or unchanging data indicates a switch or circuit failure.
Test the upshift and downshift switches for proper continuity and resistance using a digital multimeter.
Look for: Resistance values that are out of the manufacturer's specified range or an open circuit when the switch is pressed.
Inspect the wiring harness between the shifter assembly and the TCM for chafing or breaks.
Look for: Exposed copper, pinched wires, or poor pin fitment at the connectors.
Measure the reference voltage and ground at the shifter switch connector.
Look for: A lack of the expected reference voltage (usually 5V or 12V depending on the system) or a poor ground indicates a wiring issue back to the TCM.
This page explains the generic P0956 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.
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