Normal/Performance Switch Circuit
Diagnostic trouble code P0790 indicates a malfunction in the normal/performance switch circuit of the transmission. The powertrain control module (PCM) sets this code when it detects an improper voltage signal or lack of response from the switch that allows the driver to select between different transmission shift modes.
This code is generally not a safety hazard and will not strand you. However, it may prevent the transmission from entering the desired shift mode, so it should be diagnosed when convenient.
Common symptoms
- Illuminated Check Engine Light
- Inability to switch between normal and performance/sport shift modes
- Transmission shifts at incorrect RPMs for the selected mode
- Harsh or delayed shifting
- Flashing transmission or overdrive light
Likely causes
- Faulty normal/performance switch
- Damaged, corroded, or loose wiring in the switch circuit
- Poor electrical connection at the switch connector
- Spilled liquid on the center console damaging the switch
- Faulty Powertrain Control Module (PCM) or Transmission Control Module (TCM) (rare)
What to check before replacing parts
Scan for additional codes and clear the PCM.
Look for: Check if P0790 returns immediately or if other transmission codes are present, which could indicate a broader electrical issue.
Visually inspect the normal/performance switch and its wiring.
Look for: Look for signs of liquid spills (like coffee or soda) on the console, frayed wires, or loose/corroded connectors at the switch.
Test the switch for continuity using a digital multimeter.
Look for: The multimeter should show continuity changing state when the switch is toggled. If the resistance does not change or shows an open circuit, the switch is faulty.
Check the voltage and ground at the switch connector.
Look for: With the key on, verify that the reference voltage (usually 5V or 12V depending on the system) and ground are present. Missing voltage indicates a wiring or module issue.
Test the circuit from the switch to the PCM/TCM.
Look for: Check for continuity and resistance in the wiring harness between the switch and the control module. High resistance or an open circuit indicates a wiring harness failure.
This page explains the generic P0790 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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