P1746 EPC Solenoid Open Circuit
The P1746 code indicates that the Engine Control Module (ECM) has detected an open circuit in the Electronic Pressure Control (EPC) solenoid circuit. The EPC solenoid regulates transmission line pressure based on load and throttle position. An open circuit means there is a break in the electrical path, preventing the solenoid from functioning properly. This can cause harsh or erratic shifting, slipping, or transmission damage.
1. Symptoms You Will Notice
- Check Engine Light illuminated
- Harsh or delayed shifting
- Transmission slipping or stuck in gear
- Reduced fuel economy
2. Most Common Causes
- Faulty torque converter clutch (TCC) solenoid with internal coil damage
- Short circuit, open circuit, or abnormal resistance in the TCC circuit wiring or connectors
- Low automatic transmission fluid (ATF) level or contaminated/degraded fluid affecting hydraulic pressure
- Internal mechanical failure in the transmission valve body or torque converter assembly
- Powertrain Control Module (PCM) with outdated software or intermittent internal fault
3. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect wiring and connectors for damage or corrosion.
Step 3: Test EPC solenoid resistance with a multimeter (specs vary, typically 2-6 ohms).
Step 4: Check for power and ground at the solenoid connector with key on.
Step 5: If wiring and solenoid are good, test ECM output or replace ECM.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended. Driving with an open EPC solenoid can cause harsh shifting, transmission slipping, and potential internal damage. Have it diagnosed and repaired promptly.
How much does it cost to fix?▼
Repair costs vary. Replacing the EPC solenoid typically costs $150-$400 including parts and labor. If wiring repair is needed, it may be less. ECM replacement is more expensive.
5. Commonly Affected Makes
This is a manufacturer-specific code. The exact manufacturer is not confirmed in our current database.