P0790 Normal/Performance Switch Circuit Malfunction

The P0790 trouble code is an OBD-II diagnostic trouble code related to the Normal/Performance switch circuit in a vehicle's transmission control system.

P0790 – Normal/Performance Switch Circuit Malfunction

This code means that the Transmission Control Module (TCM) or Powertrain Control Module (PCM) has detected an abnormal electrical signal from the Normal/Performance mode switch circuit.

The Normal/Performance switch allows the driver to select different transmission operating strategies. In Normal mode, the transmission generally prioritizes smooth operation and fuel economy. In Performance mode, the control system may modify shift timing, shift points, throttle response, or other transmission parameters to provide a more responsive driving experience.

When the TCM receives a signal that does not correspond to the expected switch position or electrical state, it can store P0790.

What Does P0790 Mean?

Many vehicles use a switch or button to allow the driver to select between different transmission modes.

Depending on the manufacturer, these modes may be called:

• Normal

• Performance

• Sport

• Power

• Economy

• Tow/Haul

• Winter

• Snow

The exact terminology and operation vary by vehicle.

The basic system can be represented as:

Driver Mode Switch → Electrical Circuit → TCM/PCM → Transmission Control Strategy

When the TCM detects a problem in this circuit, it stores:

P0790 – Normal/Performance Switch Circuit Malfunction

The code does not necessarily mean that the transmission itself is mechanically damaged.

What Is the Normal/Performance Switch?

The Normal/Performance switch is an input device used by the driver to request a particular transmission operating mode.

Depending on the vehicle, pressing the switch may cause the TCM to change:

• Shift points

• Shift timing

• Shift firmness

• Torque converter lock-up strategy

• Engine braking

• Throttle-related transmission behavior

A Performance or Sport mode may keep the transmission in lower gears longer and delay upshifts.

A Normal mode may prioritize smoother operation and fuel efficiency.

Symptoms of P0790

Symptoms can vary considerably between vehicles.

Possible symptoms include:

• Check Engine Light

• Transmission warning light

• Normal/Performance mode unavailable

• Sport mode not working

• Performance mode switching off unexpectedly

• Transmission stuck in one operating mode

• Incorrect shift strategy

• Delayed upshifts

• Earlier-than-expected upshifts

• Harsh shifting

• Reduced transmission responsiveness

• Transmission entering fail-safe mode

• Mode indicator not illuminating

• Mode indicator remaining on

• Intermittent mode operation

In some vehicles, the only symptom may be the Check Engine Light.

Common Causes of P0790

Faulty Normal/Performance switch

The switch itself may have worn or damaged internal contacts.

Damaged switch wiring

A broken, shorted or damaged wire can cause an incorrect signal.

Loose connector

A poor connection can prevent the TCM from correctly detecting the selected mode.

Corroded terminals

Corrosion increases electrical resistance and can interfere with the switch signal.

Water intrusion

Moisture inside the switch or connector can create an intermittent electrical problem.

Blown fuse

If the switch circuit receives power through a fuse, a blown fuse can disable the circuit.

Poor ground

An inadequate ground can produce an incorrect switch signal.

Short circuit

The circuit may be shorted to power, ground or another circuit.

Open circuit

A broken wire or disconnected connector can prevent the TCM from receiving the switch input.

Damaged shift-control assembly

On some vehicles, the mode switch may be integrated into the gear selector or center-console control assembly.

Faulty TCM/PCM

A problem with the module's input circuit can cause P0790.

Communication problem

On some modern vehicles, the switch input may be processed through another control module and communicated to the TCM over the vehicle network.

Is P0790 Serious?

P0790 is generally less serious than a code indicating a transmission pressure, gear-ratio or internal transmission fault.

In many cases, the vehicle can still be driven normally.

However, the transmission may no longer operate in the requested Normal or Performance mode.

If the vehicle also has:

• Harsh shifting

• Limp mode

• Incorrect gear selection

• Transmission slipping

• Loss of drive

then the problem should be diagnosed promptly.

Can You Drive With P0790?

In many cases, yes, temporarily.

If the transmission shifts normally and the only problem is that Normal/Performance mode does not function, driving to a repair facility is generally possible.

However, if the vehicle enters limp mode or develops severe transmission symptoms, continued driving should be avoided.

What Happens When the Normal/Performance Switch Fails?

The exact response depends on the manufacturer.

The TCM may:

• Default to Normal mode

• Disable Performance mode

• Ignore the switch input

• Store a fault code

• Illuminate the Check Engine Light

• Use a predetermined transmission strategy

• Enter a fail-safe mode if other faults are present

Therefore, P0790 does not always result in the same driving symptoms.

How to Diagnose P0790

Because P0790 is a switch-circuit malfunction, the diagnosis should begin with the switch and its electrical circuit rather than assuming a transmission problem.

1. Scan the vehicle

Use a diagnostic scanner capable of communicating with the TCM.

Check:

• Stored codes

• Pending codes

• History codes

• Freeze-frame information

Look for additional codes involving transmission controls, communication or voltage.

2. Check the mode-switch live data

Many professional scan tools can display the status of the Normal/Performance switch.

Press the switch while monitoring the data.

The TCM should recognize the change.

For example:

Normal → Performance → Normal

If the switch is pressed but the TCM status does not change, investigate the switch circuit.

3. Check the mode indicator

Observe whether the dashboard or instrument cluster correctly displays the selected mode.

If the switch works mechanically but the indicator never changes, an electrical or communication problem may exist.

4. Inspect the switch

Check for:

• Physical damage

• Sticking buttons

• Contamination

• Broken housing

• Abnormal switch feel

A worn switch can produce an inconsistent electrical signal.

5. Inspect the connector

Look for:

• Corrosion

• Loose terminals

• Bent pins

• Damaged locking tabs

• Water intrusion

6. Inspect the wiring

Check the complete circuit for:

• Open circuits

• Short circuits

• Chafing

• Pinched wires

• Melted insulation

• Previous poor repairs

7. Check the fuse

If the switch circuit is fuse-protected, verify the relevant fuse.

Do not replace a repeatedly blown fuse without determining why it is blowing.

8. Check switch voltage

Depending on the circuit design, measure the voltage supplied to the switch.

Compare the result with the manufacturer's specifications.

9. Check switch resistance

Some systems use a simple resistance-based switch circuit.

Different switch positions may produce different resistance values.

Compare the measured values with the vehicle's factory specifications.

10. Check continuity

Verify continuity through the switch and wiring.

An open circuit where continuity should exist indicates a circuit problem.

11. Check for short circuits

Test the circuit for:

• Short to ground

• Short to power

• Short to another circuit

12. Check the TCM input

If the switch and wiring test correctly but the TCM does not recognize the mode change, investigate the TCM input circuit or communication system.

Can a Bad Switch Cause P0790?

Yes.

A defective Normal/Performance switch is one of the most straightforward causes of this code.

Internal switch contacts can become worn or contaminated.

The switch may then send the wrong electrical signal to the control system.

Can Wiring Cause P0790?

Yes.

A damaged wire can create an open or short circuit.

Intermittent wiring faults can also cause the mode to switch unexpectedly or stop working.

Can a Bad Connector Cause P0790?

Yes.

Loose or corroded terminals can interrupt the switch signal.

This is particularly important when P0790 appears intermittently.

Can a Blown Fuse Cause P0790?

Yes, depending on the vehicle's circuit design.

If the Normal/Performance switch receives its power through a fuse, a blown fuse can disable the switch circuit.

However, the reason the fuse failed should also be investigated.

Can P0790 Cause Transmission Problems?

P0790 primarily concerns the mode-selection input rather than a mechanical transmission component.

However, the transmission may operate differently because the requested driving mode is unavailable.

For example, Performance mode may normally alter shift timing. If the switch fails, the transmission may remain in its default strategy.

Can P0790 Cause Limp Mode?

It can, depending on the vehicle and the presence of other faults.

P0790 alone may simply disable the Normal/Performance mode.

If other transmission faults are present, the TCM may activate a more restrictive fail-safe strategy.

Can P0790 Cause Harsh Shifting?

Possibly.

The switch itself does not normally control hydraulic pressure directly.

However, if the TCM receives an invalid mode command or defaults to a different transmission strategy, shift behavior can change.

If harsh shifting occurs, additional transmission codes should be checked.

Can P0790 Cause Transmission Slipping?

P0790 alone does not normally indicate mechanical transmission slipping.

If the vehicle is actually slipping, diagnose the transmission separately and check for additional codes.

Can P0790 Cause a No-Start Condition?

Normally, no.

The Normal/Performance switch is generally not part of the basic engine-start authorization system.

A no-start condition should be investigated separately.

P0790 vs. P0700

These codes are often confused.

P0790 – Normal/Performance Switch Circuit Malfunction

Identifies a specific problem with the mode-switch circuit.

P0700 – Transmission Control System Malfunction

Is a general request indicating that the TCM has stored one or more transmission-related faults.

P0700 often appears together with a more specific TCM code.

P0790 vs. P0710

P0790 concerns the Normal/Performance mode switch circuit.

P0710 concerns the transmission fluid temperature sensor circuit.

They involve completely different systems.

P0790 vs. P0840

P0790 relates to the Normal/Performance switch.

P0840 relates to the Transmission Fluid Pressure Sensor/Switch "A" circuit.

P0840 is therefore directly related to transmission pressure monitoring, while P0790 is primarily a mode-selection input problem.

Common Diagnostic Mistakes With P0790

Replacing transmission components

P0790 does not automatically indicate an internal transmission problem.

Replacing the TCM immediately

The switch, connector, wiring and power supply should be tested first.

Ignoring the switch

A worn mode button can be the simplest cause.

Ignoring fuses

A power-supply problem can disable the switch.

Checking only the physical operation

A switch can click normally while its electrical contacts are faulty.

Ignoring live data

Watching the TCM's interpretation of the switch can quickly determine whether the input is being recognized.

What Is the Correct Repair for P0790?

The repair depends on the confirmed cause.

Possible repairs include:

• Replacing the Normal/Performance switch

• Repairing damaged wiring

• Repairing an open circuit

• Repairing a short circuit

• Repairing connector terminals

• Cleaning corrosion

• Repairing water intrusion

• Replacing a blown fuse after correcting the underlying problem

• Repairing the gear-selector or mode-switch assembly

• Restoring power or ground

• Repairing communication wiring where applicable

• Updating TCM software

• Reprogramming the TCM

• Replacing the TCM when confirmed defective

How to Test the Vehicle After Repair

After the repair, verify that:

• Normal mode is recognized

• Performance mode is recognized

• The mode indicator works correctly

• The TCM live data changes when the switch is operated

• The switch signal remains stable

• Wiring remains secure

• Transmission operation changes appropriately between modes

• No additional transmission codes are stored

• P0790 does not return

A road test should be performed in both Normal and Performance modes when the vehicle is equipped with both.

Frequently Asked Questions About P0790

What does P0790 mean?

P0790 means the vehicle's control system has detected a malfunction in the Normal/Performance mode switch circuit.

Does P0790 mean the transmission is bad?

No. It is primarily an electrical switch-circuit fault.

Can a bad mode switch cause P0790?

Yes.

Can wiring cause P0790?

Yes. Open circuits, shorts, damaged wires and poor connections can cause the code.

Can a blown fuse cause P0790?

Yes, depending on the vehicle's circuit design.

Can P0790 cause harsh shifting?

It can affect transmission shift strategy, but severe harsh shifting should prompt additional diagnosis.

Can P0790 cause limp mode?

It can, depending on the vehicle and whether other transmission faults are present.

Can I drive with P0790?

Usually, if the vehicle shifts normally and only the Normal/Performance function is affected. Severe transmission symptoms require prompt diagnosis.

Does P0790 require transmission replacement?

No. Transmission replacement is generally not justified based on P0790 alone.

Final Thoughts on P0790

P0790 – Normal/Performance Switch Circuit Malfunction is primarily an electrical input problem involving the transmission's Normal/Performance mode selection system.

The most important thing to understand is that this code does not automatically indicate an internal transmission failure.

The recommended diagnostic path is:

Switch → Fuse → Connector → Wiring → Power/Ground → Live Data → TCM

A faulty switch, corroded connector, damaged wire or power-supply problem can all prevent the TCM from correctly recognizing the selected driving mode.

If the vehicle still shifts normally, P0790 is often a relatively straightforward electrical fault. However, if the code is accompanied by limp mode, harsh shifting, slipping or loss of drive, additional transmission codes should be investigated before the vehicle is driven extensively.