15/06/2026 6:12 am
Topic starter
Automotive Q&A
Parasitic draw wakes to 420 mA every 15 minutes after the truck goes to sleep
Review the evidence, add a focused answer, and distinguish confirmed measurements from assumptions.
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A 2018 F-150 settles near 24 mA about 40 minutes after shutdown, then rises to 420 mA for roughly 90 seconds every 15 minutes. Doors and hood are latched, keys are stored away from the vehicle, and no aftermarket equipment is visible. Pulling fuses during the wake period is difficult because the next cycle may not be identical.
What is the least disruptive way to identify which module is initiating the wake-up?
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16/06/2026 8:52 am
Record current with a low-amp clamp or fused bypass that does not interrupt battery power, and capture network activity at the same time. Note which bus wakes first and compare module last-message or wake-reason data if the platform provides it. Voltage-drop testing across fuses can help locate the active branch without removing a fuse, but use a temperature-correct chart and measure during the repeatable event.
Also monitor latch, key-presence and telematics inputs. The module drawing current is not always the module that requested the wake-up, so identify the initiating message before unplugging components.
Topic starter
17/06/2026 7:22 am
The medium-speed network became active first, and the telematics module reported repeated antenna-status changes. Water corrosion was found at the roof-antenna connector. After repairing the connector, the truck slept at 23–26 mA for two hours with no 420 mA cycles.