The alternator on your Toyota Previa only has three mounting bolts, a connector and 2 wires you need to remove or disconnect the replace it. However, if you have the 2TZ-FE engine, you will have to do some of the work from underneath the vehicle; if you have the 2TZ-FZE engine, you need to remove the air duct and coolant reservoir for better access to the alternator. Whichever your model, you can install a new alternator.
Park your car in a safe place, raise the front of the vehicle using a floor jack and safely support it on 2 jack stands. Remove the engine cover from underneath the vehicle using a ratchet and socket.
Open the bonnet, disconnect the wire from the alternator adjusting bar, and unplug the alternator electrical connector.
Remove the wire from the alternator using a ratchet, ratchet extension and socket to reach and remove the wire nut.
Loosen the alternator lock bolt, adjusting bolt and pivot bolt-loosen the pivot bolt from underneath the vehicle. Use a wrench or ratchet and socket; then remove the drive belt off the alternator pulley.
Remove the lock and adjusting bolts; then remove the pivot bolt from underneath the vehicle and pull the alternator off the vehicle from underneath the engine compartment.
Set the new alternator in place, working from underneath the vehicle, and install the pivot bolt; then install the adjusting and lock bolts. Install the drive belt over the alternator pulley and adjust and tighten the adjusting bolt; then tighten the lock and pivot bolts.
Plug the alternator electrical connector and wire; then install the adjusting bar wire and engine undercover.
Remove the air duct and the mounting bolts form the engine coolant reservoir; then move the reservoir to the side.
Disconnect the black, negative battery cable, then disconnect the positive battery cable and remove the battery.
Loosen the idler pulley nut from the centre of the pulley-the idler pulley is located next to the alternator; then loosen the pulley adjusting bolt located behind the idler pulley. Lift the drive belt off the alternator pulley.
Unplug the alternator electrical connector and the wires from the alternator and alternator upper bracket.
Remove the three alternator mounting bolts using a wrench and ratchet and socket; then lift the alternator off the engine compartment.
Set the new alternator in place and tighten the three mounting bolts; plug the alternator electrical connector and connect the alternator and bracket wires.
Install the drive belt over the alternator pulley and adjust the belt by tightening the idler puller adjusting bolt; then tighten the pulley centre nut.
Install the battery, coolant reservoir and air duct.