P0790
UniversalNormal/Performance Switch Circuit Malfunction
Medium SeverityThis code indicates that the Powertrain Control Module (PCM) has detected an electrical problem within the circuit for the transmission mode switch, which allows the driver to select between normal and performance shifting modes. This malfunction can prevent the driver from changing transmission shift patterns and may lead to the transmission operating in a default mode.
⚠️ Before You Begin (Safety First)
Always ensure your vehicle is safely supported on jack stands if working underneath. Disconnect the battery before performing any electrical repairs to prevent accidental shorts or injury. Allow the engine and transmission to cool down before handling any components.
Common Symptoms
- Check Engine Light illuminated
- Inability to select different transmission modes (e.g., Sport, Economy)
- Transmission may operate in a default "limp home" mode
- Unexpected or harsh shift points
- Transmission may feel "stuck" in a particular mode
Common Causes
- Defective transmission mode switch
- Corroded or damaged wiring in the switch circuit
- Loose or corroded electrical connectors
- Faulty Powertrain Control Module (PCM), though less common
- Short circuit or open circuit within the switch wiring
Frequently reported on: General/Universal
Diagnostic Steps
- Visually inspect the transmission mode switch and its electrical connector for any signs of damage, corrosion, or loose connections.
- Check for any obvious damage to the wiring harness leading to the switch.
- Using a multimeter, test the continuity and resistance of the switch circuit according to your vehicle's service manual specifications.
- Clear the P0790 code and test drive the vehicle to see if the code returns.
- If the switch is determined to be faulty and accessible, replace it.
👨🔧 When to Call a Professional
If after inspecting the visible wiring and connectors, the issue persists, or if you suspect an internal transmission problem, it is best to consult a professional mechanic for advanced diagnostics.
Commonly Asked Questions
What does a P0790 code mean?
The P0790 code indicates a malfunction in the electrical circuit of the transmission's normal/performance mode switch, which controls different shifting characteristics.
Can I still drive my car with a P0790 code?
While it may be possible to drive, it's not recommended for extended periods. The transmission might operate in a default mode, affecting performance and potentially causing further damage if not addressed.
What are the common symptoms of a P0790 code?
Symptoms typically include the Check Engine Light, inability to switch transmission modes, unexpected shift patterns, or the transmission feeling like it's stuck in a specific mode.
How difficult is it to fix a P0790 code myself?
Diagnosing electrical circuit issues can be moderately challenging, requiring a multimeter and a good understanding of wiring diagrams. Replacing a faulty switch might be simpler once identified.
What parts are usually involved in a P0790 repair?
The most common parts involved are the transmission mode switch itself, and potentially wiring or connectors in its circuit.