Hello all, first post here to the blazer forum, the posts here have helped me tremendously. I have a 2001 blazer 2 dr 4x4 LS 172k on her. current issue is intermittent no start from the passkey system and my interior lights are always on unless i push the dome override button. Also note that while driving, if you lock the doors all doors lock except the drivers door. It will lock and unlock rly fast. start from the beginning with what all ive found, fixed and tried..

When i got the truck i found doors falling off, and an amature radio job, among a list of other things...

- found power door locks not working, found blown fuse, replaced.

- Replaced all door pins.

- Found wires to ignition switch spliced, red to yellow i think, well i propperly soldered and shrink wrapped them back how they SHOULD be from the factory.

- Found wire nuts on radio connection adapter falling off/ bare wires, did same to those wires as well.

- I just replaced the heater core myself, and also replaced some of the damaged and missing interior plsstics at the same time. I did am A+ job on it and have quadruple checked all my connections and visible wiring afterwards. That dosent seem to be the issue.

- I have disconnected my drivers side door jamb switch, lights still on, ohm'd the switch and its good, found that passenger side door jamb switch is not connected to anything, i read some blazers are like that?

- i even replaced my drivers side door latch module thinking it got beat up from the sagging door, light is still on.

- I replaced the courtesy light relay under the dash, still on.
dimmer switch is working propperly..

I even tried the "bcm reset" where you disconnect the battery leads and hold them together for 10 seconds, lights still on.



Ok so basicly now im led to belive i have one of the follwing issues.

A. The bcm is malfunctioning

B. I have a shorted wire somewhere

C. ??????

I have spent days trying to figure it out, read literally dozens nof threads and nothing ive tried worked. Any input is really appreciated!

 

Doubtful it's the BCM. Disconnecting the battery does not reset anything, except maybe radio stations, and the clock, but nothing in the BCM or PCM is reset. Driver door locking and unlocking while driving is a problem. If the driver door is open when you hit "lock", it will unlock immediately when you release the switch, that is normal operation. This might be a clue to the interior lights staying on too.


Interior lights staying on could be a problem with RAP, (retained accessory power), but more than likely it's a jamb switch. Possibly the tail gate or even one or more door jamb switches. All door jamb switches need to be connected, even the passenger door, if you want it to work.

 

Thanks Captain, that seems logical that the vehicle thinks the drivers door is open. That was my first though when i decided to change out the drivers side power door latch assembly with one snatched from a junkyard. I read the assembly has a sensor built in that tells the bcm when the door handle is lifted, and that will activate the courtesy lights/ security system. I have checked the door jamb switches and they ohm out in accordance with open and closed positions, but its possible that fact the passengers door jamb switch is not connected as something to do with this issue too.
It is also worth mentioning when i pulled the original door latch module i failed to figure out how to check the lift sensor... so i basically replaced it with the best looking one i could find in the junkyard. I could not find a source to guide me on checking it either, no could i find resources explaining where i could find where the passenger door switch could wire into

Guess i have two objectives now.

A) figure out how to propperly test that latch switch

B) figure out where the hell the pass side door jamb switch is supposed to connect to the wiring harness

Thanks for helping me norrow this down a bit. I dont like to just throw parts at it.

 

The switches in the door handles are for illuminated entry. There are two wires at the switch, and you'll need an ohm meter to test the switches in both doors. Un plug the connectors: Test resistance between the two terminals on the switch. With the handle in the "rest" position, it should show an open circuit. When you lift the handle it should show less than 5 ohms.


There are two relays in a relay block, just to the right of the instrument panel fuse block. One is the courtesy lamp relay, the other is the inadvertent power lamp relay. If either relay is stuck, the courtesy lights will not shut off.


If you remove the passenger side kick panel, (just forward of the door, by the passengers feet), you should be able to find the connector for the passenger door jamb switch dangling in there somewhere.


Courtesy lights are supplied battery voltage at all times through an orange wire. The various switches ground the wire and the lamps come on.

 

Mkay, got some results now..
i bench tested my old power latch with my feildpiece multimeter. In the rest position it registered roughly 60 ohms, as well as in the open position. That did not add up to me so i pulled my door panel and checked ohms on my replacement junkyard latch, found 4.9 ohms in rest position, as well as open position..
im not rocket scientist but i think i both my old and new latches have bad switches.. guess ill have to pull a new one, but at least i know how to check it hopefully thats the issue.


On another note, i searched hi and low and was not able to find a connection from the main harness under the dash or under the carpet to hook up the passenger side jamb switch. Even oulled back the carpet and the doorway trim, no 2 wire connector to be found.

 

Okayyy finally after 3 weeks i figured it out. It is the passenger side door latch stuck open. I unplugged it and 20 seconds later the lights whent out. I have everything all back together minus the connection to the latch. Thanks again for helping me troubleshoot captain, you rock!

 

If you unplug the handle switches, it should solve the problem, but you won't have illuminated entry. If you want it to work, sounds like you need two new switches.

 

Update. I have solved the courtesy light issue. I ended up replacing both driver and pass door latch modules. Still having the intermittent no start with a flashing security light. I replaced my ignition switch with a brand new acdelco. No issue for about 12 start ups untill this morning.

I have not tried the key re-learn yet, as im doubtful that will solve the issue?

Any advice as to where i should go from here?
Im not ready to give up on this truck yet!
Thanks guys

 

Well i decided to go ahead and try to bypass the passlock system with the resistor method some have described. Figured why not since my old igntion switch is good, might as well experiment with it. I cleaned the contact points then re installed it. I then measured the resistance generated by the passlock sensor, it was consistantly 3.4k ohms. Got a 3.3k as it wss the closest i could find from radio shack, and soldered it in to the switch wiring. After i plugged it all back in, the truck would just crank and security light flashed. I went ahead and performed the key relearn procedure...

It seems to have been successful as the truck now starts up. Ive set the alarm, returned and started it back up several times today with no issue. Ill give it some time and report back how it holds up for anyone who may be interested. Thats all for now.

 

The ignition lock cylinder mechanically moves the ignition switch to the various positions. Neither one of those parts are "technically" part of the Passlock system.


The ignition lock cylinder fits into the ignition lock housing, which has a sensor for the key built in to it. If the sensor does not send correct, or complete data to the BCM, the BCM will not authorize the PCM to enable the fuel injectors. Dorman Products - 924-713