P0790 Normal/Performance Switch Circuit Malfunction

P0790 points to a normal/performance switch circuit malfunction. The transmission mode or performance selector input is not behaving as expected.

Code details

Generic OBD-II · P0

System: Transmission
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not chase shift timing complaints before confirming the mode switch input is valid.

Symptoms of P0790

Harsh, delayed, or slipping shifts, or being stuck in one gear.
Check-engine light, sometimes with limp-home mode.
Flaring RPM or a shudder under load.

Common causes of P0790

Low or degraded transmission fluid.
A failing speed sensor, shift solenoid, or pressure-control circuit.
Wiring, connector, or internal hydraulic/mechanical faults.

Useful checks before replacing parts

Compare switch position data with the actual selector state and check whether the module sees normal and performance modes correctly.
Inspect switch wiring, connector fit, water intrusion, center-console damage, power feed, ground, and module input voltage.
Check whether shift schedule, indicator lamp, or mode display symptoms match the switch circuit fault.

Related OBD-II codes

These nearby transmission entries can help compare wording and pin down the fault area.