P0815: Upshift Switch Circuit

What it means

The TCM detects an electrical fault on the manual upshift request switch (paddle or +/- lever) circuit.

At a glance

• Usually lights the check-engine light

How it works

The upshift switch sends a manual upshift request from a paddle or selector control to the transmission control module (TCM). The TCM monitors the switch circuit and sets P0815 when it detects an electrical fault in that upshift request path. The transmission may ignore manual upshift requests even if automatic shifting still works.

Common causes

Most likely first.

1. Switch contacts failed
2. Wiring open

Symptoms

• Manual upshift request may not be recognized
• Check-engine light may be on

How to diagnose it

1. Save freeze-frame data and scan for transmission codes, then check live data to see whether the TCM recognizes an upshift request.
2. Operate the upshift paddle or selector switch while stationary and note whether the request appears consistently in live data.
3. Inspect the upshift switch, steering-wheel or selector connector, and accessible wiring for looseness, wear, or corrosion.
4. Test switch continuity and the upshift circuit for opens or shorts using the manufacturer's procedure.
5. If the switch and wiring pass, check the TCM connector and input circuit before considering a module fault.

Common fixes

• Repair an open or damaged upshift switch wire.
• Clean or repair a loose or corroded upshift switch connector.
• Replace the upshift switch if it fails the manufacturer's continuity or function test.
• Repair a TCM input fault only after confirming the switch and circuit are sound.

Can I keep driving?

If automatic shifting works normally, you can usually drive cautiously while avoiding reliance on manual upshifts. Stop if the transmission also shifts unpredictably, loses drive, or enters a fixed gear.