Shift/Timing Solenoid Intermittent
Your transmission's shift solenoid is cutting in and out intermittently, like a light switch that keeps flickering on and off. This prevents smooth gear changes and can cause unpredictable transmission behavior.
The ECM monitors solenoid coil resistance and control signal voltage to the shift/timing solenoid. It detects intermittent opens or shorts by checking for unexpected resistance changes and signal dropout during normal operation cycles.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Solenoid Coil Resistance | 5-15 ohms (varies by solenoid type) | Open circuit or resistance spikes indicating intermittent connection |
| Control Signal Voltage | 12V when activated, 0V when deactivated | Erratic voltage fluctuations or signal dropout |
Code P0804 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, P0804 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.