P0790 Code Meaning and Next Steps

First checks take 10 to 20 minutes for the first checks. No special tools are usually needed for the first checks.

Can you keep driving?

Stop driving if any of these apply

!The transmission starts slipping or refusing to shift correctly.
!The vehicle enters limp mode or the issue affects safe gear selection.

If the light is steady and the vehicle still drives normally: Maybe, but only for a short distance if the transmission still shifts normally.

What to check first

Step-by-step checks

1
Free - no tools
Check whether the switch or mode input feels normal and whether the gear selector or drive-mode behavior matches the display
2
Free - no tools
Inspect the switch connector and harness for looseness, corrosion, or recent disturbance
3
Basic tool needed
Check for other transmission or body-control codes that might share the same input path
4
Basic tool needed
If scan data is available, compare the commanded switch state with the live input reading
5
Basic tool needed
If the fault appeared after service or interior work, verify that no connector was left loose

If the code returns

-If the input changes when the connector is moved, focus on the wiring path before replacing the switch.
-If the switch tests good but the code remains, the control module or shared circuit becomes more likely.
-If the code returns after repair, confirm the input behaves consistently across several drive cycles.

Background

What this code means

P0790 is a generic OBD-II code for the normal/performance switch circuit.

That circuit is often tied to a driver-select or transmission-mode input, so the real issue is usually electrical, switch-related, or a shared control-path fault rather than a major mechanical failure.

Treat it as a circuit diagnosis first and a component replacement second.

Diagnosis

Common causes

Most common

Mode or range switch failure

The switch may not report the expected state to the ECU.

Common

Connector or harness issue

Loose connectors, damage, or corrosion can interrupt the input signal.

Common

Shared circuit problem

Another module or input path may be affecting the reading.

Possible

Transmission control issue

The controller may not be interpreting the switch signal correctly.

Avoid these mistakes

What not to do

xDo not replace the switch first if the connector, wiring, or shared circuit has not been checked.
xDo not ignore other module codes that may explain the input signal problem.

Parts

Parts that may need replacing

PartTypical costNotes

Mode or range switch$30-$180Relevant when the switch itself does not report the correct state.

Connector pigtail repair$20-$120Worth checking if the plug or pins are damaged.

Harness repair$30-$200Useful when the input path is intermittent or broken.

Related OBD codes

P0705

P0705 usually means the transmission range sensor circuit is not behaving correctly.

P0700

P0700 usually means the transmission control system has a fault stored in the transmission module.

Source notes

Generic OBD-II (SAE J1979 / ISO 15031-5). P0790 was expanded around normal/performance switch circuit faults, including switch, wiring, and shared-input issues.

This guide is written as a generic multi-make reference, so bulletin history, sensor locations, and repair order can still change by manufacturer and engine family.

This is generic OBD-II guidance and should not override vehicle-specific service information. Exact diagnosis and repair steps vary by make, engine family, and model year.

Last reviewed: 2026-04-10

Reference: Open reference

P0790 - P0790 Usually Means Normal/performance Switch Circuit Malfunction