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Virtual Technician, ASE Certified Technician
Category: Car
Satisfied Customers: 96
Experience:  25 years Experience. All makes and models, Shop Owner, Access to 4 repair databases. - I take the Opt Out Questions :)
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Mazda B2500: 1998 mazda B2500 battery keeps draining caused

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1998 mazda B2500 battery keeps draining caused by fuse # XXXXX in the I/P. Pulling .45 amps when I connect the battery. Description on fuse legend is "GEM/CTM, Instrument cluster". I can't find this circuit in the owner's manual or a Haynes. Any idea how to further investigate and what the wiring diagram looks like? Any help would be greatly appreciated. Need for work on Monday!
Hi, I'm a Moderator for this topic. I've been working hard to find a Professional to assist you right away, but sometimes finding the right Professional can take a little longer than expected.

I wonder whether you're ok with continuing to wait for an answer. If you are, please let me know and I will continue my search. If not, feel free to let me know and I will cancel this question for you. Thank you!

Hi my name is XXXXX XXXXX I'll try my best to help with your vehicle issue.

***Please note: Not every answer I give you is something you were hoping to hear, even though it is true.
Such as; (it's more expensive than you wanted to spend, or you will need to have a professional repair shop do the diagnostics and /or repairs due to complexity reasons).

Here is a diagram to the BCM:


1. Do you have any warning lights on when vehicle is running?

2. Do you have a scanner capable of getting into the Body Control Module?

Here is the wiring to the cluster (gem module):


As you can see - when the power goes into the module(s) - it is dispersed FROM it to LOTS of items.

It could be a bad BCM, GEM module, or cluster and will take some time to track everything down.

Do you have a digital multimeter?


Is there ANYTHING else that is not functioning correctly?

Customer: replied 4 years ago.

Yes, I do have a digital meter. I may have a buddy that has a scanner for the BCM which would probably be the most valuable troubleshooting I could do. I will check with him tomorrow.


1. The warning flashers stay on when the battery is connected. I used to be able to push the theft deterent button to turn off the flashers but this does not work. I would like to permently disconnect the theft deterent but do not know how. Any suggestions on where to start?

2. Is it correct to say since I do not have electric windows I have a BCM instead of a GEM?


3. I have a strong background in electronics and controls troubleshooting. The images you sent will be a big help but since I do not see a way to isolate each CTM output I will probably need a full set of wiring diagrams to get much further. Any further tips or guesses on the most likely items?

I just thought of something - when are you checking the draw from fuse 25?

Here's why I ask:

Most 1995 and newer Ford/Mazda products have modules in them which will remain in "standby" mode for a period of time after the vehicle is shut off. While in this mode, they will draw current which is excessive by established standards for normal current drain. However, after no longer than 1 hour of inactivity (no change in state of door switches, door handle switches, hood switch, trunk/tailgate switch, ignition switch or key-in-ignition switch), they should go to sleep, and total current draw should be less than 50 mA.


Before we head down a wrong path

1. Fully charge the battery

2. Hook up meter as described in next test - make sure it's visible from inside the vehicle

3, Locate and Pull all fuse covers inside vehicle

4. Go to the restroom

5. Then grab a flashlight,

6. Get a good book, (you're going to be inside the truck for a while)

7. You'll need needle nose pliers and perform the following test:


MY summary of the issue - please correct me if I am wrong.~~~~~~~~
Vehicle Application:
1999 Ranger 2.5 / B2500
Customer Concern:Electrical drain causing the battery to go dead. When pulling fuse #25 (7.5 amp) from the interior fuse box the drain goes away.
Tests/Procedures:1. Install an ammeter between the battery negative post and cable to identify the amount of amperage draw that is present on the vehicle. A normal draw will indicate approximately 250 milliamps (mA) for 45-60 minutes after all doors are closed with the ignition switch off. After that time frame, the Generic Electronic Module (GEM) will enter a sleep mode and the total vehicle drain should decrease to indicate 50 mA or less.

2. If the amperage draw is normal when initially turning the ignition switch off with the doors closed, but it stays close to 250 mA after the 60 minute wait period, remove fuse #25 to see if the mA draw drops to less than 50 mA indicating a defective GEM.

3. If the draw is higher than either of the normal specification values, start pulling all interior fuse box fuses one at a time until the draw drops under an acceptable level to determine the circuit and components which are influencing the excessive draw. Leave the fuses out as they are pulled to prevent awakening any modules which could result in falsified readings.

4. If all interior fuse box fuses are removed and the draw is still excessive, start removing the under hood fuses one at a time until the drain drops to an acceptable level to identify the circuit of concern. Again leave the fuses out as they are pulled to prevent waking up any on-board module.

5. Once the fuse of concern has been identified, reinstall the fuse and start disconnecting all related components of that circuit to identify if the draw is related to a component issue or a circuit problem.
Virtual Technician, ASE Certified Technician
Category: Car
Satisfied Customers: 96
Experience: 25 years Experience. All makes and models, Shop Owner, Access to 4 repair databases. - I take the Opt Out Questions :)
Virtual Technician and 7 other Car Specialists are ready to help you

Thank you for the positive feedback :)
I'm glad we got it figured out.
Part of the reason I decided to participate in this forum was not only to help people on here but also to further my knowledge for my own shop here in WI.

I would be interested in knowing what you found out from the testing I sent you as to what the issue ended up being.

Thank you in advance for taking the time to tell me so that I may also help others.