Upshift Switch Circuit
Diagnostic trouble code P0815 indicates that the powertrain or transmission control module has detected an electrical fault in the upshift switch circuit. This code is set when the computer receives an erratic, missing, or out-of-range voltage signal from the switch used to manually command a transmission upshift.
This code is generally not a safety concern and will not strand you. The vehicle will typically continue to shift normally in standard automatic 'Drive' mode, though the manual upshift feature will be disabled.
Common symptoms
- Illuminated Check Engine Light
- Inability to manually upshift the transmission using the shifter or steering wheel paddles
- Manual shift mode may be completely disabled by the transmission controller
- Transmission shifts normally in standard automatic mode but ignores manual inputs
- Gear indicator on the dashboard may not reflect manual mode selection
Likely causes
- Faulty upshift switch (shifter assembly or steering wheel paddle)
- Liquid spilled on the center console shifter assembly causing a short
- Damaged, corroded, or loose wiring and connectors in the upshift switch circuit
- Faulty steering wheel clockspring (if equipped with paddle shifters)
- Defective Transmission Control Module (TCM) or Powertrain Control Module (PCM)
What to check before replacing parts
Connect an OBD-II scanner to verify P0815 and check for other transmission codes.
Look for: Confirm P0815 is the primary code; if other communication or shifter codes are present, they may indicate a broader electrical issue.
Visually inspect the wiring and connectors around the shifter assembly or steering column.
Look for: Look for chafed wires, disconnected plugs, or signs of corrosion that could interrupt the switch signal.
Inspect the center console shifter area for signs of liquid intrusion.
Look for: Sticky residue or corrosion on the shifter circuit board indicates a spilled beverage likely caused the switch failure.
Use a scan tool with live data capabilities to monitor the upshift switch PID.
Look for: The scan tool should show the switch state change from 'OFF' to 'ON' when the upshift paddle or lever is activated. If it doesn't change, the switch or circuit is dead.
Test the upshift switch directly using a digital multimeter.
Look for: Check for proper continuity and resistance values when the switch is pressed according to the manufacturer's service manual; infinite resistance when pressed indicates a failed switch.
This page explains the generic P0815 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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