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Persistent Battery Drain on 2017 Civic Si - What's causing it?

0

Chris P. · rep 0 · May 22, 2:47 AM · 1 replies · solved · Question

Vehicle: 2017 Honda Civic Si

My 2017 Honda Civic Si keeps having its battery drain, sometimes overnight, sometimes over a couple of days. I've replaced the battery twice in the last year, thinking it was just a bad battery, but the problem persists. The car often struggles to start, or won't start at all.

I've checked for lights left on and made sure everything is off when I park. Could there be a parasitic draw somewhere? I'm not getting any warning lights on the dash, which makes it harder to diagnose.

What are common culprits for battery drain in these Civics? Are there any specific modules known to cause this, or TSBs I should be aware of?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 2:47 AM

0

A persistent battery drain, especially after replacing the battery multiple times, strongly indicates a parasitic draw in your 2017 Honda Civic Si. This means something is drawing power even when the car is off. Diagnosing this can be tricky but is essential.

Here are common culprits and steps:

  1. Hands-Free Link (HFL) Module: This is a very common issue in older Honda models, though less frequent in newer ones, it's still worth checking. A faulty HFL module can stay active and drain the battery. You might notice issues with Bluetooth connectivity if this is the case.
  2. Aftermarket Accessories: Any non-factory installed items (stereo, alarm, dash cam, remote start) are prime suspects for parasitic draws if not wired correctly.
  3. Faulty Relays: A relay that sticks in the 'on' position can keep a circuit active, draining the battery. Common culprits include the main relay or relays for accessories.
  4. HVAC Blower Motor Resistor/Module: Sometimes, the blower motor or its control module can fail in a way that causes it to draw power even when the car is off.
  5. Infotainment System: As mentioned in another thread, infotainment systems can sometimes have software glitches that prevent them from fully shutting down.
  6. Charging System Check: While you've replaced the battery, ensure your alternator is charging it correctly. A failing alternator won't keep the battery topped up, leading to similar symptoms. A simple voltage test can confirm this (should be 13.5-14.5V when running).

When to See a Shop:

  • Professional Diagnosis: A parasitic draw test requires a multimeter and patience. If you're not comfortable performing this yourself, a qualified technician can systematically test each circuit by pulling fuses while monitoring the current draw. They can identify the specific circuit and component causing the drain.
  • OBD Codes: While you might not have dash lights, a professional scan tool might reveal 'ghost' codes (e.g., U0100, U0121, B1000 series) related to communication errors or module failures that could point to the culprit.
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