1. Low transmission fluid. If your transmission fluid is low, the hydraulic pressure needed to engage the gears may not be sufficient, causing the engine to stall. Check the transmission fluid level and add fluid if necessary.
2. Faulty transmission position sensor. The transmission position sensor tells the engine control unit (ECU) which gear the transmission is in. If the sensor is faulty, it may send the wrong signal to the ECU, causing the engine to stall. Have the transmission position sensor checked by a qualified mechanic.
3. Faulty neutral safety switch. The neutral safety switch prevents the engine from starting unless the transmission is in neutral. If the switch is faulty, it may not properly engage, allowing the engine to start but preventing the transmission from engaging the gears. Have the neutral safety switch checked by a qualified mechanic.
4. Faulty clutch (manual transmission). If your truck has a manual transmission, a faulty clutch may prevent the transmission from engaging the gears. Check the clutch for wear or damage and have it replaced if necessary.
5. Faulty flywheel or flexplate (automatic transmission). In an automatic transmission, the flywheel or flexplate connects the engine to the transmission. If the flywheel or flexplate is damaged or cracked, it may not be able to properly transfer power from the engine to the transmission, causing the engine to stall. Have the flywheel or flexplate inspected by a qualified mechanic.
