Avital 4105L Unlock and Start Fail

I'm SO frustrated! Chrysler 1998 Town and Country LX 3.8L Gas only engine. Avital 4105L remote starter (1 way with keyless entry). The lock/unlock system is a "1 wire type". For anyone who doesn't know, this means that on the NORMAL door lock/unlock switch in the car (assuming no remote start module has been installed yet), the door lock switch connects the SAME wire from the BCM to ground whether you are locking or UNlocking the door. The only difference is how much resistance there is in the connection. The switch has TWO different resistors in it. The BCM wire has a 5v signal at rest. When you LOCK the doors with the switch, you connect that signal wire to ground through a 1500 OHM resistor. When you UNlock the doors with the switch, you connect the SAME signal wire to ground through a 250 OHM resistor. Then, the BCM tells the PCM to ground the relay for either the lock or unlock function, depending on how much voltage drop the BCM sees when you flip the switch (more drop with locking than unlocking, because the resistance is higher through the LOCK resistor). When connecting the remote start module, the module is NOW taking the place of the door switch. However,, you have to trick the BCM into thinking that it is the regular switch because the remote start module is not designed with these different resistors in the ground path. The module is designed as if the car uses different wires for lock and unlock, NOT the same wire through different resistances. Therefore, I wired in a 1500 OHM resistor between the lock/unlock harness at the remote start module (herein referred to as the "rsm") lock pin and the BCM 5v signal wire. I also wired in a 250 OHM resistor between the RSM unlock pin and the BCM 5v signal wire. The door LOCK function works perfectly. The UNlock function NEVER works! Please offer any thoughts or advice on how to troubleshoot or fix this issue. It is a BIG deal, b/c it means I'll have to carry both the factory and the RS key fobs at all times which is, let's face it, a pain in the ass! Second problem: I am 100% positive I installed all the wires in the correct places. I tested them with a meter, I checked bulldog security, and I have all the factory wiring diagrams right out of the factory service manual which I studied intently. However, the rsm will crank but will not start the engine. I tried turning off the virtual tach feature and increasing crank time to 2 seconds but NOTHING is working. I have sunk over 20 hours into this installation already. PLEASE! Someone give me some troubleshooting tips to fix this SOB. There is a device called an auto-shutdown relay involved here which I think may have something to do with why it's not starting but I'm really not sure. Thanks so much to anyone who can help.

For the unlock in not sure on your issue as I have the same resistance info Door Lock     WHITE/ Dark Green      BCM at Fuse Panel 1500 Ohm Resistor Door Unlock     WHITE/ Dark Green      White Connector B58 Connector 250 Ohm Resistor Maybe try metering the unlock wire and see what voltage you get using the switch then meter the wire using the remote start remote see if they are the same value ? For the starting portion can you list your wiring for us. Also what color key do you have (gray or black) ? If gray what bypass are you using ?If i Can't Install it    I Don't need it   Joe

Your so close, thanks for the very thorough explanation. Chev is right, check the outputs to see if the resistance is correct. It won't be. The outputs from the Avital are not from relays, therefore there is some resistance already present. A few options 1. Add a relay to the unlock output of the avital so you have s good ground output to work with (use the same resistor). 2. Adjust your unlock resistor, you can even try it without one at all. It may work. 3. The factory door lock relays are at the bottom of the fuse box on that van. Pull the relays half way out and find the ground trigger on the coil then just solder your unlock from the remote start that pin. Good luck.

Thanks so Much. From the wiring diagrams, it looks like the relays are actually built into the housing of the BCM and Junction block. I don't believe that they are accessible externally on the junction block. That is my great frustration with this whole deal. If they were easily accessible, I would have just spliced the unlock trigger right into the coil on the relay. Unfortunately, that wire or pcb pathway is completely enclosed in the housing of the BCM. I might try splicing the unlock wire into the passenger side unlock switch wire pin instead of the driver's side because they both have the same result in the vehicle. Currently I have both the lock and unlock remote start wires spliced into the same pin which is the driver side switch pin on the BCM. I'll let you know what happens. Really appreciate the help. I will also try it without the resistor. Thanks

You need to use those door lock outputs from the RS module to trigger relays to send your ground signals to the BCM, you can't just put the resistors on the outputs from the RS module. Use DEI's 451M door lock relay module.

Why is this necessary and if that's true, why does the LOCK function work withOUT a door lock module?

Haven't had time to check the output resistance or voltage of the unlock wire on the RSM. HOWEVER, I did figure out why the crank, nostart condition existed. FUEL PUMP RELAY failed. HOPING this was a coincidence and not something caused by the RSM wiring. I couldn't start from the key either, so I checked the relay and found HIGH resistance in the coil, but it was intermittently high or normal depending on when I placed my meter probe on the terminals. I figured it was worth the 15 dollar relay (O'reilly's was sold out of the 7 dollar one) to get my wife off to work the following morning. Popped the relay in and BOTH key and RSM fire engine right up now. FY baby! FY! (FY is an acronym for a less than savory phrase it's probably inappropriate to use in the forum). UNlock still not working but I haven't done anything different yet. Didn't have time. Can't thank you guys enough. IF it's possible that the RSM blew the coil in the Fuel Pump relay (like, if this is a common problem with RSMs), please let me know what likely caused it so I don't do it again! Thanks so much. This forum rocks. Everyone is so kind and really fast with the replies. I'm very impressed!

Ooooh, you're right! The unlock relay IS accessible on the front of the junction block! Sorry to have doubted you. I'm going to give this "tapping into the coil ground side" a try and I'll let you know what happens. Awesome man. This website is fantastic.

Good news. I remember some of them have 2 relays and others 3. The third would be for the driver's door (priority unlock). Now, you have two options. 1. Send your unlock output to both relays. 2. Remove the relay and if I remember correctly theres a spot for a 30 amp fuse to make all the doors common. Either way, this should work.