Lockup Solenoid System
The torque converter lockup solenoid isn't engaging or disengaging properly, preventing the transmission from efficiently locking the engine to the wheels. Think of it like a clutch that's stuck and won't fully engage or release.
The ECU monitors lockup solenoid current draw and response time to verify proper engagement and disengagement. It detects electrical faults or mechanical failures when actual transmission behavior doesn't match commanded solenoid state. Thresholds monitor voltage, amperage, and lockup timing.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Solenoid Current Draw | 0.5–2.0 amps | Below 0.3 or above 2.5 amps |
| Lockup Response Time | 100–400 ms | Above 600 ms or no response |
Code P1742 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, P1742 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.