What Happens When a Vacuum Modulator Goes Bad? Understanding the Symptoms and Solutions
When a vacuum modulator goes bad, it can cause a variety of problems in an automatic transmission. The modulator controls the shifting of the transmission by measuring the engine vacuum and sending a signal to the transmission valve body. If the modulator fails, the transmission may shift too early or too late, or it may shift harshly. Other symptoms of a bad modulator include transmission fluid leaks, rough idling, and decreased fuel economy.