P0790: Normal/Performance Switch Circuit Malfunction
The P0790 code indicates a malfunction in the normal/performance switch circuit, which is part of the transmission control system. This switch allows the driver to select between normal and performance shift modes. The Powertrain Control Module (PCM) detects an electrical issue, such as an open or short circuit, or an invalid signal from the switch. This can affect shift timing and transmission behavior.
1. Symptoms You Will Notice
- Check Engine Light illuminated
- Transmission stuck in normal mode or unable to switch modes
- Harsh or erratic shifting
- Reduced fuel economy
2. Most Common Causes
- Faulty or stuck Normal/Performance mode switch
- Open circuit, short to ground, or short to battery in the switch circuit wiring
- Corroded, loose, or damaged terminals in the switch circuit connectors
- Internal TCM/PCM failure (uncommon)
3. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm the code and check for other related codes.
Step 2: Visually inspect the normal/performance switch and its wiring for damage, corrosion, or loose connections.
Step 3: Test the switch with a multimeter for proper resistance and continuity according to manufacturer specifications.
Step 4: Check the fuse for the transmission control system and replace if blown.
Step 5: If the switch and wiring are okay, test the PCM for proper signal reception and consider reprogramming or replacement if necessary.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is generally safe to drive short distances, but the transmission may not shift optimally, potentially causing drivability issues or further damage. It is recommended to diagnose and repair promptly.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for parts and labor, depending on whether the switch or wiring needs replacement. Diagnostic fees may be additional.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.