Faulty or worn normal/performance (mode) switch, including sticking contacts or internal failure; Damaged, corroded or loose wiring or connector at the switch or control unit; Open circuit, short to earth or short to voltage in the switch signal or reference wiring; Liquid ingress or dirt in the switch or centre console area; Fault in the transmission or powertrain control unit input circuit; Outdated control unit software where the manufacturer has issued a correction for this fault.

P0790

Normal/Performance Switch Circuit.

Generic
Powertrain
Generic code
Low severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
7: AreaTransmission
90: FaultThe specific fault in that area

What it means

P0790 is the generic code for a fault in the Normal/Performance Switch Circuit. This is the driver-operated switch that selects between transmission shift modes, such as normal, economy, sport or snow/winter. The control unit sets the code when the switch signal is out of range, stuck, erratic or does not match what it expects. How the switch is wired and what it does varies by model and transmission, so check the manufacturer's data for the vehicle.

Symptoms

Malfunction indicator lamp on, and possibly a transmission warning light
Selected drive mode does not change when the button or switch is pressed
Transmission stuck in one shift mode, often normal or a default mode
Harsh, late or unusually early gear changes
Mode indicator on the dash flickering or not matching the selection
Poor fuel economy or sluggish response if the car defaults to the wrong shift programme

Possible causes

Faulty or worn normal/performance (mode) switch, including sticking contacts or internal failurelikely
Damaged, corroded or loose wiring or connector at the switch or control unitlikely
Open circuit, short to earth or short to voltage in the switch signal or reference wiringpossible
Liquid ingress or dirt in the switch or centre console areapossible
Fault in the transmission or powertrain control unit input circuitrare
Outdated control unit software where the manufacturer has issued a correction for this faultrare

How to diagnose

Read all stored and pending codes and the freeze frame data, and note any other transmission or network codes
Operate the mode switch and watch the dash indicator and the live switch status on a scan tool to see if the signal changes
Check the switch and surrounding area for spilt drink, damage or a sticking button
Inspect the switch connector and the control unit connector for corrosion, bent pins, loose terminals and water
Wiggle test the harness with live data displayed to look for dropouts
Check the supply, signal and earth at the switch against the manufacturer's wiring diagram
Check circuit resistance and test for shorts or opens in the harness with the battery disconnected as required
Check for applicable software updates or technical service bulletins for the model before condemning the control unit

How to fix

Replace the faulty mode switch or switch assembly
Repair or replace damaged wiring, terminals or connectors, and clean any corrosion
Dry out and clean the switch area and fix the source of any liquid ingress
Repair the short or open circuit found in the harness
Replace or repair the control unit only after the switch and wiring are proven good
Update the control unit software if the manufacturer lists it as a fix for this fault

Can I keep driving?

Low severity

The car can usually be driven as the transmission normally defaults to a standard shift mode. Book it in soon, and stop driving if gear changes become harsh or the transmission goes into limp mode.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.