Torque Converter Clutch Solenoid Failied On
The torque converter clutch solenoid is stuck in the ON position, preventing proper fluid flow and locking behavior. Think of it like a stuck valve in a water pipe that won't open or close when commanded.
The ECM monitors solenoid coil resistance, current draw, and response time during torque converter clutch engagement/disengagement cycles. It compares actual hydraulic pressure feedback against expected values for each gear and throttle condition. A stuck-ON solenoid causes abnormal pressure readings and prevents proper clutch modulation.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Solenoid Coil Resistance | 5-15 ohms | Open circuit or shorted (0 ohms or >20 ohms) |
| Clutch Lock-up Response Time | 200-600ms | No response or continuously energized |
Code P1748 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.
Once the fault is repaired, P1748 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.