Shift/Timing Solenoid Range/Performance
Your transmission's shift solenoid isn't responding correctly to electrical commands from the engine computer. Think of it like a valve that won't open or close properly when signaled—the transmission can't shift smoothly or at all.
The ECM commands the shift solenoid to modulate transmission fluid pressure by sending a variable voltage signal. It monitors solenoid resistance and current draw to verify the solenoid responds within expected electrical parameters and timing windows. If actual response deviates from commanded values, a range/performance fault is triggered.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Solenoid Coil Resistance | 4-10 ohms (varies by design) | Out of range or shorted/open circuit |
| Solenoid Response Time | 50-200 milliseconds | Delayed or no response to command signal |
Code P0790 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, P0790 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.