Toyota 25870-74090 Modulator Assy, EGR Vacuum

To reduce oxides of nitrogen emissions, some exhaust gases are recirculated through the EGA valve to the intake manifold, lowering combustion temperatures. The EGA system includes the EGA valve, EGA modulator (in some models), vacuum switching valve, Electronic Control Module (ECM), and various sensors, with the ECM programmed to produce the ideal EGA valve lift for each operating condition. To check the EGR valve, start the engine and let it idle, then detach the vacuum hose from the EGA valve and attach a hand vacuum pump. Apply vacuum to the EGA valve; it should remain steady while the engine runs poorly. If the vacuum is unstable or the engine runs normally, replace the EGA valve and recheck. If the vacuum is steady but the engine runs normally, remove the EGA valve to check for blockages in the valve and intake manifold, cleaning or replacing parts as necessary. For the EGR vacuum modulator valve, remove the valve, pull off the cover, and check the filters, cleaning them with compressed air before reinstalling. Further checks of the EGA systems require special tools and should be performed at a dealer service department. For component replacement, detach the vacuum hose, disconnect the threaded fitting from the EGA valve, remove the mounting bolts, and take out the EGA valve to check for sticking or carbon deposits, cleaning or replacing it as needed. Installation follows the reverse order of removal, and for the EGR vacuum modulator, label and disconnect the vacuum hoses before detaching the modulator from its bracket, with installation also being the reverse of removal.

Disconnect the negative battery cable, then raise the vehicle and place it securely on jackstands.