Power lock issue

[OTB]

First off, just want to say hello since this is my first post.
I will do an official introduction post later if anyone really give a sh.. who I am. lol

Just got my '99 Limited the other day, all works fine until a few days later. Isn't that always the case?

Well, power locks half way stopped working.
It will still unlock the doors but they won't lock the doors.
Neither switch or by double turning the key (using the key will lock the door it is in only).
I don't have a key fob yet but I am guessing if I did it will be the same anyways.
I would guess it to definitely be something electrical and not mechanical since there is no clicking sound or anything. I would also guess it to not be as simple as a fuse since they will unlock just fine.

Without diving in, I will also guess there is probably some central location that this problem would come from since it is not likely for both switches and keys going out all at the same time.

Any suggestions?

 

[EatonKyleH]

First off, just want to say hello since this is my first post.
I will do an official introduction post later if anyone really give a sh.. who I am. lol

Just got my '99 Limited the other day, all works fine until a few days later. Isn't that always the case?

Well, power locks half way stopped working.
It will still unlock the doors but they won't lock the doors.
Neither switch or by double turning the key (using the key will lock the door it is in only).
I don't have a key fob yet but I am guessing if I did it will be the same anyways.
I would guess it to definitely be something electrical and not mechanical since there is no clicking sound or anything. I would also guess it to not be as simple as a fuse since they will unlock just fine.

Without diving in, I will also guess there is probably some central location that this problem would come from since it is not likely for both switches and keys going out all at the same time.

Any suggestions?

Welcome!
Well sorry to start your journey off on a bad note but I'd highly recommend taking this to a professional.

Here is a little something I pulled up on my archives at work documenting common problems.

Complaint:
The power door locks will unlock but will not lock. Doesn't make a difference whether the key fob, key cylinder or the switches in the doors are used, it will not lock it, just unlocks.

Diagnosis:
Check power and grounds for Body ECU.
Check voltage on all of the unlock request circuits at the Body ECU. There should be a 12v reference until the switch closes and then it should go to 0 volts. If it does not the Body ECU is faulty

The common failure item associated with this complaint is the Body Control Module (Body ECU) but again I'd take it to your tech to preform these diagnostics before just ordering parts because occasionally it is a simple power/ground problem.

Just wanted to share some info and point you in a good direction.

 

[ajonesnv]

My 99' does a similar thing. They will work if the truck is on or if they are not on the sun side of the truck, heat seems to drain their power...sounds funny, but that is the case.

Havent given it much concern since I try to just manually lock and unlock anyway.

 

[TheDurk]

I looked at the schematics and I have some feedback for you. But, to save me a lot of typing, please answer the following:

-Did you try the PASSENGER door lock switch? (It's on a separate input circuit.)
-Are BOTH your dome lights operating normally--back with back, 4 fronts with front--with all FIVE doors? (We need to eliminate the possibility of a bogus 'door open' signal that would block the lock function.)

Thanks.

 

[OTB]

Yup, both switches don't work and yes the dome lights all seem to work fine.

 

[TheDurk]

Yup, both switches don't work and yes the dome lights all seem to work fine.

That's too bad, actually. That being the case, I don't see much possibility that does not involve a new Body ECU. Ideal would be to find one to swap as a test. To be thorough, you could run through the tests laid out on p. 121 of the wiring manual here:

F:/Dada/DurkDocs/Manuals%20&%20Tech/Auto/Toyota/1996%20to%202002%20Toyota%204Runner%20Repair%20and%20Wiring%20Manuals/1996%20to%202002%20Toyota%204Runner%20Repair%20and%20Wiring%20Manuals/techinfo.toyota.com/ileaf/ewdtmc2/ewdtmpdf/ewdsourc/2002/024runne/systemci/032dlc.pdf

The pinout for the Body ECU is at B16 here:

http://tacoma.site40.net/4Runner_96-02_Repair&Wiring/techinfo.toyota.com/ileaf/ewdtmc2/ewdtmpdf/ewdsourc/2002/024runne/connecto/connecto.pdf

If I had a pass/fail for each of these, I might be able to guess at a cause, but it would likely be internal to the Body ECU.

Or, do as EatonKyle suggests and let a pro eff with it.

Final thought (H/T to ajones above) Have you tried it with truck running? It may be a voltage insufficiency thing. Check that battery is fully charged and that close to full battery voltage is present at terminals 3 and 10 of the Body ECU.

 

[OTB]

So would the body ecu affect other things with the engine too?
Because it also idles rough now at a stop.
Seems to run smooth when I give it gas but idles rough when stopped.

 

[TheDurk]

So would the body ecu affect other things with the engine too?
Because it also idles rough now at a stop.
Seems to run smooth when I give it gas but idles rough when stopped.

Not that I can think of. Low battery voltage/failing alternator might, though.

 

[EatonKyleH]

So would the body ecu affect other things with the engine too?
Because it also idles rough now at a stop.
Seems to run smooth when I give it gas but idles rough when stopped.

Your running concern would be something unrelated to the Body ECU. If you can live with the lock issues than you will most likely be able to leave the Body ECU alone.

Just to add to Durks pass/fail probability of the Body ECU. We've replaced 5-6 of these for this same issue over the last 2 years. Its not the most common thing in the world but you are explaining the symptoms exactly. I just hate to tell you to replace it without having someone verify its bad that's all.

 

[OTB]

Thanks guys