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Hello,
Have a 2019 Ford F-150 2.7L eco boost with an odd draw. With tester setup, current will drop to around .050 amp, every minute or so it will jump to approximately .700-.800 amp for a few seconds then ramp back down for a minute. I found disconnecting the ABS module the draw will completely go away. With a scope on the CAN lines going to the abs module, every time the current jumps, there is a communication packet being sent out as if a module is sending a message. Any guidance on where to start would
Be much appreciated!
Recently saw a video from Ivan at Pine Hollow Diagnostics that found the telematics module was causing intermittent parasitic draw on a Lincoln. The reason for that was because it was 3G and couldn't communicate with 4G. But was behaving somewhat the same way as your description.
Might possibly give you a direction to take a peek at:
Maybe try eliminating all the outputs of the abs module. Use jumper wires from the harmess to the powers and grounds and com wires to the pins of the module itself
In terms of inputs/outputs from the abs module, there isn’t many. Other than the 4 wheel speed sensors, electronic park brake switch, the electronic park brakes, brake vacuum sensor, the 2 can wires, 3 powers and 2 grounds
Pulling the 40amp fuse from the battery fuse box also gets rid of the draw and the communication problem. I attached a picture of the wiring diagram. Hopefully you can see that
That is something I will check. There was a
U0121:00 Lost Communication With ABS Control Module: No Sub Type Information Stored in the park aid module after I cleared dtcs from unplugging the module. I am not sure if this is a current dtc or not. I will have to clear again on Monday and see if it comes back. The module is integrated into the bcm. They don’t talk directly to each other either as one is on the hs1 can and the other on the hs2 where they meet at the gateway module. There are no errors or other issues with the vehicle
Just wanted to update this for anyone in the future. Turns out the electronic park brake switch was sending some sort of signal every minute to the abs module keeping it awake. New switch fixed the issue
The OEMs don't seem to publish (at least not to the general public) how the vehicles should enter sleep and / or wake up. Meaning we do not have a known good system description of how sleep works in a comprehensive way (like current versus time graph). Which means we have to reverse engineer proper operation as we troubleshoot which is why parasitic draw problems are so time consuming.
First of all it would be good to know how long with a properly functioning vehicle does it take to have the vehicle go to sleep. Many times this is not known, which means we use a rule of thumb like 30 minutes and just monitor the parasitic draw current to see what it does.
The way I do this is to put a battery sustainer on the vehicle so as to not run down the battery in the middle of a test and to also put a slight charge on the battery, which is needed anyway because the battery is usually drained. Then I make sure the vehicle thinks the doors are latched (manually throw the latches) and any other conditions for sleep and then I monitor the parasitic draw current with my PicoScope at the battery and wait 30 minutes to see what is does. A scope provides more information than a DMM, and many time any periodic event can give a clue to the cause.
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