99 CTD Sport Dead Batteries

Hi All!
Finally discovered the problem causing high IOD draw and a couple of sets of dead batteries.
Was about to change out the ignition switch .... pulled out fuse instead for
the Seat Belt Control module. This solved the problem. Seat Belt Control module was back feeding circuit ACC 31 which was keeping the radio and wipers on with the ignition shut off.
Anyone replaced one of these Seat Belt control modules? Cost info?
TIA
Fred
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Did you also disconnect the wiring harness to the Central Timer Module to verify that was indeed the cause of the backfeeding? It's accessible by removing the panel below the steering column. It's the electornic box on the right-hand side of the dash frame. Remove the two screws, and you can pull the module out far enough to disconnect the electrical connector.
If it does need to be replaced, it's going to be a dealer job. Not because you can't put a new one in (that's the simple part), but the new CTM needs to be programmed with all of the features in your truck (power windows/locks, keyless entry, steering wheel radio controls - all stuff like that).
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Hi Tom! Thanks for the heads up.
Didn't disconnect the CTM ... when I removed the fuse for the Seat Belt Module killed the back feed to the wipers and radio as these are fed from a common circuit ACC 31.
What would be the symptoms to look for if the CTM has failed?
Is the CTM feed from the ACC 31 circuit as well??
Fred

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Okay - you should do that, and check the radio with it disconnected. You want to make sure it's really a fault inside the CTM, and not a wiring problem, or even some other component that's back-feeding the accessory circuit. If you disconnect the wiring from the CTM, and the radio's still energized, well - it's obviously not a problem within the CTM itself. After that, I'd try the radio (disconnect it, re-connect the CTM, and see if the wipers work with the ignition off).

Yes . it's got a couple of different power feeds into it... one is an always-on feed from the battery, the other is the ACC31 circuit from fuse #6.
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This doesn't sound like a way to be removed from the "yardbird advice watch list." Keep it up old boy.

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Problem definitely is the Seat Belt Control module. Pulling the fuse that feeds the SBCM solved the problem I was having with high IOD and killing both batteries in about a week.
CTM is working properly.
Can't find this part (SBCM) listed at any of the online parts houses.
Anyone ever changed one of these modules? Any ideas on how much they are?
TIA
Fred

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Okay, my mistake. In later years, all these functions were incorporated into the CTM. However, in '99 (and probably earlier years, as well), there is indeed a separate SBCM that handles these functions (seat belt switches, solenoids, door ajar switches, etc.)
Have you disconnected the SBCM at the wiring harness, again to verify that the SBCM is really at fault, and not the wiring? It's located underneath the front seat center console.

Looks to be a little over $100 - I saw one quoted for $118.
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Thanks for the info Tom! The saga continues ...
After removing the center seat I finally got at the Seat Belt Control Module and disconnected it.
Checked for voltage again at fuse 16 with the ignition off. Voltage still present at this fuse with the ignition key off. Fuse 15 that has a common feed according to the Service Manual is fine... no voltage present. Checked all other fuses with the same feed in the Junction Block, (6, 8, 10 and 15) and they are all at 0 volts with the ignition turned off as they should be.
Looks like it is a Junction block problem. I notice the Service Manual states that if this occurs the entire Junction Block has to be replaced ! !
Can only imagine how much fun it's going to be to replace the Junction Block after removing seats to get at the Seat Belt Control Module.
Anyone ever changed out the Junction Block on a 99 Sport Quad CTD??
Fred

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So let me get this straight... even with the SBCM unplugged, ignition off, you get voltage through fuse 16. Are you saying that even with fuse 16 installed, you read 0 voltage on fuse 15, or are you saying that with fuse 16 removed, then fuse 15 shows 0 volts as it should?
If it's the latter, I'd strongly suspect a short in the wiring out to the SBCM, before I'd suspect a bad junction block.

Not exactly, but I've done work behind the dash. It's actually not all that bad... remove the 5 screws up on the top of the dash, at the base of the windshield. Remove the steering wheel knee blocker panel, and remove the steering column support. Rest the column on the seat, and loosen (but do not remove) the two big hex bolts on either side of the dash, under the side kick panels, that hold the dash frame to the body. Allow the dash to roll forward, resting on the seat. You can then reach from the driver's side, over the dash, and disconnect all the connectors from the junction block, and remove it. Of course, disconnect the battery/batteries first, and let the truck sit for several minutes to let the capacitators in the airbag module bleed off.
I still vote for short in wiring myself, but that's just a percentage call...
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Hi Tom !
With the SBCM unplugged the top of fuseholder 16 (fuse removed) is 13.6V positive to ground ...the bottom of the fuseholder is 0.0V (fuse removed) the top of fuseholder 15 is 0.0V to ground (fuse removed) and the bottom of the fuseholder is at 0.0V. Same readings for all other fuses commoned on this circuit in the Junction Block (6, 8, and 10). All fuses are fed from the same source according to the SM diagram.
The kicker here is that if the top of fuse holder 16 is live with the ignition key off ... they should all be live ... but they aren't.
If there is a short ... it is has to be in the Junction Block itself ....SM says in this case that you have to change out the Junction Block.
Fred

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Okay - one last thing.... did you pull each fuse in succession to figure out where the feed to #16 is coming from?
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Well that was fun ... stripped all the wiring harnesses under the seat... examined all the wires ... wires all fine. Examined all the connectors ... connectors all look fine...no signs of overheating on any connector body or terminal.
With the harness all stripped I started probing around with a meter and noticed each time I turned C303 in my hand the resistance would change between the blue and pink conductors... pink conductor is from the IOD fuse which is fuse 12. Blue conductor from fuse 16 is terminated in C303 right next to the pink conductor.
Finally getting really frustrated with not being able to physically see any defects in the wiring I decided to connect everything back up except for the Seat Belt Control Module and put the fuses back in. Then to give the circuit some load I turned on the windshield wipers with the ignition off and turned C303 back and forth ... sure enough a mini light show going on inside C303!!!
Bottom line is ... not a wise design choice to terminate both these feeder conductors right next to each other in the same connector body.
Thanks for all your suggestions Tom ... much appreciated!!
Fred
PS Didn't order a seat heater with the truck but some options come for free I guess! 8-)

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Glad I could help out (and glad you didn't wind up changing out the junction block). Seems to me the easiest fix would be to cut one of the two wires from both sides of the connector (I think you mean C360, not C303 - but no matter), solder a little extension on both sides, and use another type of quick connector on it (I personally like the Posi-Lock connectors).
Aren't electrical problems fun to troubleshoot? :)
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Especially the "intermittent" types!
Sure glad I didn't have to get into the Junction Block ... had half the cab torn apart as it was! 8-)
Fred

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Another thing to help narrow things down... you've identified the circuit that's getting back-fed - ACC-31, from fuse 16. Now you need to identify which circuit is doing the back-feeding. Pull fuse 16, and fuse 12. Then, check for continuity between the "load" terminals of each fuse (meaning the terminal that feeds the circuit - not the terminal that gets +12V from the battery).
If you get continuity, and I suspect that you will, you need to trace the wiring out the the SBCM, and look closely at both the dark blue and the pink wires. Also check joint connector #5, which is on the driver's side of the knee blocker panel opening, inside the dash. If you disconnect this connector, and repeat the continuity test above, you can isolate whether the short is between the junction block and the joint connector, or by checking the pink and dark blue wires on the connector, if the short is downstream towards the SBCM.
Good luck
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Thanks for your suggestions Tom.
I'm assuming the top of the fuseholders are the "feed" side ... could be that the feed is actually bottom terminal of the fuseholders.
Going to follow up tomorrow.
Fred

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