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Seat belts will not release

Tiny
JMUNRO
  • MEMBER
  • 1999 DODGE RAM
  • 5.2L
  • V8
  • 4WD
  • AUTOMATIC
  • 150,000 MILES
Both seat belts will not release. I checked the wiring to the seat belt control module and found no current (*or voltage) across the pink and green/black. I did not get anything across the fuse sets either. I am thinking that I might not be getting power to the fuse. Is there a relay that sends this? Thanks. John
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Saturday, November 4th, 2017 AT 3:09 PM

13 Replies

Tiny
STEVE W.
  • MECHANIC
  • 13,002 POSTS
You should have twelve volts on the pink wire all the time and twelve volts on the dark blue wire with the ignition on. The green/black is the signal wire from the airbag module and should not be probed as you could trigger the belt tension-ers.
Fuses twelve and sixteen power it.

Fuse sixteen comes from the ignition switch and is powered through the same circuit that powers the radio and wipers.

Fuse twelve is fed from the battery through Fuse one (50 amp) in the PDC.

If you have no power at either fuse and the radio works and the radio retains memory and clock, the issue is inside the PDC.
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Monday, November 6th, 2017 AT 7:44 AM
Tiny
JMUNRO
  • MEMBER
  • 8 POSTS
Thanks, Steve. Probably a dumb question, but what is the PDC? The pink wire I was checking was at the connector to the seat belt control module. If not the green/black, where should I put the negative probe to in order to test? I tried the frame and still nothing. I will test these other things you mentioned. Appreciate your expertise. Thanks. John
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Monday, November 6th, 2017 AT 8:18 AM
Tiny
STEVE W.
  • MECHANIC
  • 13,002 POSTS
PDC - Power Distribution Center - AKA the underhood "smart" fuse box

For a ground I usually use the battery negative, engine block, or chassis. I also have 20 foot test leads that I can use as needed.
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Monday, November 6th, 2017 AT 2:26 PM
Tiny
JMUNRO
  • MEMBER
  • 8 POSTS
Thanks, Steve. Any idea which fuse in the PDC might be going to fuses 12 and 16 in the fuse box? The wipers, radio, etc. Are working and I do not get any power at 16 and probably not 12. Thanks. John
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Monday, November 6th, 2017 AT 4:46 PM
Tiny
STEVE W.
  • MECHANIC
  • 13,002 POSTS
Fuse 1 in the PDC powers fuse 12 in the junction fuse box. It is a 50 amp that powers multiple circuits.
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Tuesday, November 7th, 2017 AT 6:38 AM
Tiny
JMUNRO
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  • 8 POSTS
Thank you, Steve. John
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Tuesday, November 7th, 2017 AT 7:14 AM
Tiny
JMUNRO
  • MEMBER
  • 8 POSTS
Hi, Steve. I found I was using a poor ground, so I went to the battery like you said. Fuses 12 and 16 in the fuse block are good, after all. Fuse 1 in the PDC appears fine. Wipers and radio work. But, still no power to the pink wire at the seat belt control module using this battery ground. I do not see any obvious breaks in the wiring from under the seat and under the carpet floor cover, but kind of hard to follow it up into the fuse block. Any final thoughts on this? Thanks again for all your help. John
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Tuesday, November 7th, 2017 AT 3:24 PM
Tiny
STEVE W.
  • MECHANIC
  • 13,002 POSTS
Check to see if you have power at pin 16 in the OBDII connector, it is powered on the same circuit. It should have 12 volts with the key on. If it does but the seat belt module still doesn't you have a break in the wiring from the junction 5 connection to the module. You could just run a new pink wire to bypass the current one.
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Tuesday, November 7th, 2017 AT 7:28 PM
Tiny
JMUNRO
  • MEMBER
  • 8 POSTS
Hi, Steve. So, I jiggled a whole bunch of wires under the dash and I now have power to the blue wire (with the ignition on) and a good ground (light green and black wire) at the wiring harness for the seat belt control module. Still no freedom of the seat belts when I plug the module back into it, so I'm thinking that it is likely the module. It does seem a little weird to have the other issues we discussed and then for them to resolve so easily and then to be able to isolate it to the module. I didn't do anything intelligent to them. Is there a way to test the module before spending the $130 +? Thanks. John
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Wednesday, November 8th, 2017 AT 1:30 PM
Tiny
JMUNRO
  • MEMBER
  • 8 POSTS
Hi, Steve. I think I solved my question. I temporarily hooked the orange wire of the passenger seat belt servo to the blue of the seat belt control module harness and the light green of both the servo and sbcm harnesses (bypassing the seat belt control module) and was able to release that seat belt. Looks like it was the seat belt control module, after all. I'm going to see if I can pick one up used at the salvage yard and will let you know if it works. Thanks. John
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Wednesday, November 8th, 2017 AT 4:07 PM
Tiny
STEVE W.
  • MECHANIC
  • 13,002 POSTS
Was going to suggest bypassing the module as a way to test it. Good job.
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Wednesday, November 8th, 2017 AT 11:30 PM
Tiny
JMUNRO
  • MEMBER
  • 8 POSTS
Hi, Steve. Today is a good day. I got a seat belt control module at the salvage yard and both seat belts work. Weird thing about the wiring situation that jiggling fixed and to have the final problem be the module, but I'm OK with being lucking every 50 years. Thanks so much for your help, you've got some skills. John
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Thursday, November 9th, 2017 AT 3:06 PM
Tiny
STEVE W.
  • MECHANIC
  • 13,002 POSTS
You would be shocked at how many times I've repaired a "serious issue" on a vehicle by jiggling the wires, they get loose, corrode and lose contact over time.

Luck wasn't it, you traced the problem and fixed it. Now if you walked out there and whacked it on the hood like "The Fonz" and it worked, that would be luck.

Thank you for using 2CarPros. Com
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Thursday, November 9th, 2017 AT 7:14 PM

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