From a troubleshooting standpoint I'm glad it doesn't have the theft deterrent system (less potential problem spots). The starter circuit is actually quite simple on the automatic "plain Jane" Previas. Aside from the wiring and connectors, the AM1 circuit goes directly from the battery through the 50A AM1 Fusible link and then directly to the ignition switch via a white wire. After the ignition switch it goes to the neutral start switch (via a black/white wire) then to the starter via a black wire. You could probably start swapping parts and get lucky, but I would recommend getting a volt meter and doing some troubleshooting.

1st thing to do is access the wire connector going to your ignition switch and pull it apart. Inspect the conductors inside to make sure they are clean and shiny. Pay particular attention to the black & white wire and the associated pin (connector position 7) as this is the circuit in question. If the pins look good then plug it back together and try to start. If it starts then you will need to drive or whatever to make it act up. Once you get it to act-up, check the voltage of the bigger white wire and compare to the voltage of the black-white wire during a start attempt. The difference in voltage between these two wires S/B less than 1 volt (.5V or less drop is preferred). If you see a big drop here (more than 1 volt) then the switch is bad and needs to be replaced. If that checks out then climb under the van, pull the trigger wire from the starter and carefully inspect (make sure it's clean and tight). Warning: make sure vehicle is secure on jack stands, emergency brake set and gear shift in park before climbing under van!

If the ignition switch and the visual inspection of connectors is satisfactory then go to the passenger's side front of the transmission and find the neutral start switch (see picture below)


As with the ignition switch, unplug the wire harness and inspect the plug to make sure it's clean and shiny inside. If all looks good, reconnect it and pull back the wire cover to expose the wires inside. Find the black/white & black wires (black/white is position 3 and black is position 2). The black/white wire comes from the ignition switch and the black wire goes to the starter. Using your meter have a helper try to start the van and compare voltages. Again you should see no voltage drops more than 1 volt. If there is a significant drop in voltage between these 2 wires then the neutral switch is the problem.

Note 1: At no point should you see less than 10 volts in this circuit. If voltage is low then you will need to back-track towards the battery until you identify the spot where the voltage is dropping. If you find such a spot, this will be the source of your problem.

Note 2: The wire harness is wrapped and concealed pretty good so it will be difficult to track the wires. Hopefully this won't be necessary (problems are usually failed components).

Good luck with your troubleshooting and I hope you have success. I looked up the ignition switch and see it's still available new. For the 91 Previas it's Toyota part #84450-28070 and sells for around $95 on discount internet Toyota sites like www.1stToyotaParts.com. Hopefully it's not the neutral start switch as this is NLA new (at least for 91). According to my search, 92 & up switches are available, but I couldn't find any notes saying if they would replace the earlier discontinued one. Keep in mind the neutral start switch is also an integral part of the electronic controlled transmission (does more than just prevent starting while in gear). As a result it's expensive (cheapest I could find was around $225). If this ends up being the problem I would probably go to a salvage yard and pull one off a 91 Previa. According the the Toyota EPC, the 91 neutral start switch is part #84540-28020. The one called out for 92 & up Previas is #84540-28021. Tim

PS: If it acts up again before you have a chance to troubleshoot, put the transmission in neutral and try again. Chances are it won't effect anything, but if it starts consistently in neutral but not in park, then the problem is in your neutral start switch.