Pressure Control Solenoid 'C' Control Circuit Low
The P0966 code indicates that the Powertrain Control Module (PCM) has detected a low voltage condition in the control circuit of the pressure control solenoid 'C'. This solenoid regulates hydraulic pressure within the automatic transmission to control shift timing and firmness. A low circuit condition typically means the voltage is below the expected range, often due to a short to ground, open circuit, or faulty solenoid. This can lead to improper transmission operation, harsh shifts, or slipping.
1. Symptoms You Will Notice
- Check Engine Light illuminated
- Harsh or erratic shifting
- Transmission slipping or delayed engagement
- Reduced fuel economy
- Transmission stuck in limp mode
2. Most Common Causes
- Faulty pressure control solenoid 'C'
- Open or shorted wiring in the solenoid control circuit
- Poor electrical connection at the solenoid or PCM
- Low transmission fluid level or dirty fluid
- Internal transmission mechanical failure
3. Step-by-Step Diagnosis
Step 1: Scan for additional codes and freeze frame data to confirm P0966.
Step 2: Inspect transmission fluid level and condition; top off or replace if necessary.
Step 3: Visually check wiring and connectors for damage, corrosion, or loose pins.
Step 4: Test the pressure control solenoid resistance with a multimeter (typically 4-6 ohms).
Step 5: Check for voltage and ground at the solenoid connector with the engine running.
Step 6: If wiring and solenoid are okay, test the PCM output signal; replace PCM if faulty.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive with P0966 as it can cause transmission damage. Limp mode may limit speed and prevent further damage, but you should have it diagnosed and repaired promptly.
How much does it cost to fix?▼
The cost varies depending on the cause. Replacing a solenoid can cost $150-$400 including labor. If wiring repair is needed, it may be less. Transmission rebuild or replacement can exceed $2000.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.