3-4 Shift Malfunction
Your transmission is struggling to shift from 3rd to 4th gear smoothly, like a car that hesitates when trying to accelerate up a hill. The engine control unit detected that the shift didn't happen within the expected time or pressure range.
The ECM monitors solenoid activation, transmission fluid pressure, and vehicle speed to confirm the 3-4 shift occurs within a specific time window and pressure threshold. If shift pressure is too low, duration is too long, or speed patterns don't match expected values, the fault is logged.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| 3-4 Shift Time | 200-600 milliseconds | Exceeds 800ms or fails to occur |
| Line Pressure During Shift | 50-150 PSI | Below 40 PSI or erratic fluctuation |
Code P0787 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, P0787 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.