P0790
Normal/Performance Switch Circuit Malfunction
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The P0790 code indicates a malfunction in the Normal/Performance switch circuit. Many vehicles with automatic transmissions offer a mode selector — often labeled Normal, Sport, Economy, or Performance — that adjusts the transmission's shift points, throttle response, and overall driving characteristics. This code means the Transmission Control Module has detected a problem with the circuit that communicates the driver's selected mode.
In most cases, this code does not create an immediately dangerous driving condition. The vehicle will typically default to Normal mode, and you'll simply lose the ability to switch to Sport or Performance mode. However, in some vehicles, the TCM may enter limp mode if it cannot determine the driver's intent, which would limit speed and gear selection.
This is one of the more DIY-friendly transmission codes because the mode switch is usually accessible from inside the cabin (on the center console or dashboard) and the repair often involves simply replacing the switch or cleaning corroded connections. Start by inspecting the switch and its wiring connector for visible damage. A multimeter can test whether the switch changes resistance or voltage as expected when toggled. If the switch and wiring are good, the TCM's input circuit may be at fault.
Severity
Symptoms
- •Unable to switch between Normal and Sport/Performance driving modes
- •Vehicle stuck in Normal mode or defaults to a single mode
- •Check Engine Light illuminated
- •Transmission may enter limp mode in some vehicles
- •Slightly reduced responsiveness or shift timing changes
Likely Causes
The physical switch on the console or dashboard that toggles between driving modes has worn out or failed internally, sending no signal or an incorrect signal to the TCM.
Wiring between the mode switch and the TCM may be corroded, frayed, or shorted, interrupting the low-voltage signal the TCM uses to determine the selected mode.
The electrical connector at the switch or TCM may have corroded or loose pins that cause an intermittent or complete loss of signal.
The TCM may have an internal fault in the circuit that reads the mode switch input, causing it to register a malfunction.
Estimated Cost
Professional Repair
Includes parts + labor
Common Fixes
- Replace the Normal/Performance mode switch
- Repair or replace damaged wiring in the switch circuit
- Clean corroded connectors at the switch and TCM
- Replace the Transmission Control Module if its input circuit has failed