P0797: Pressure Control Solenoid C Stuck On
The P0797 code indicates that the Transmission Control Module (TCM) has detected that the Pressure Control Solenoid C is stuck in the 'on' position, causing abnormally high line pressure in the transmission. This solenoid regulates hydraulic pressure to the clutch packs and bands; when stuck on, it can lead to harsh shifts, slipping, or transmission damage. The issue is often electrical (wiring, connector, solenoid resistance) or mechanical (blocked fluid passages, debris).
1. Symptoms You Will Notice
- Harsh or delayed shifts
- Transmission slipping or overheating
- Check Engine Light illuminated
- Reduced fuel economy
2. Most Common Causes
- Faulty pressure control solenoid C
- Wiring or connector issues (shorts, opens, corrosion)
- Low or contaminated transmission fluid
- Internal transmission mechanical failure (blocked passages, debris)
3. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Inspect transmission fluid level and condition; top off or replace if necessary.
Step 3: Visually check wiring and connectors to solenoid C for damage or corrosion.
Step 4: Test solenoid resistance with a multimeter (compare to specs, typically 4-6 ohms).
Step 5: Perform a transmission pressure test to verify line pressure is excessive.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended. Driving with high line pressure can cause harsh shifts, transmission slipping, and internal damage, potentially leading to costly repairs.
How much does it cost to fix?▼
Repair costs range from $150 to $400, depending on whether the solenoid alone needs replacement ($50-$150) or if additional wiring, fluid, or labor is required.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.