Hey everyone,
I’m hoping to get some help tracking down a parasitic drain on my 2019 Acura RDX A‑Spec SH‑AWD. The issue started in December 2025 and has been ongoing despite multiple attempts to fix it. I’ve already done my own testing, swapped the 12V battery several times, and even brought the car to the nearest Acura dealership twice. Unfortunately, the drain is still there, and since the car has been out of warranty since April 2025, I’m hesitant to keep letting the dealer throw parts at it.

**My testing:**
- Consistent draw of **3.6–3.8 amps**
- Verified with both a DC amp clamp and a multimeter in series
- Pulling **Fuse #37 (Audio, 15A)** drops the draw to **1.8 amps**
- Next step: disconnecting the trunk amplifier power harness to see if it drops further

**Timeline:**
- **Apr 2024:** Replaced original AGM battery with Costco Interstate
- **Dec 20, 2025:** Battery dead → Costco warranty replacement
- **Dec 29, 2025:** Dead again → Costco replacement
- **Jan 4, 2026:** Dead again → Costco replacement
- **Jan 6–8, 2026:** Dealer replaced negative ground cable + negative terminal sensor
- **Jan 9–14, 2026:** Returned to dealer; car died while they had it → BCM replaced
- Still pulling **3.6 amps** afterward
- Pulling audio fuse still drops it to **1.8 amps**

At this point it seems like something in the audio circuit is staying awake, but I’m not sure where to go next. Any advice or similar experiences would be appreciated.

 

I don't know what the normal draw is for the RDX, but I would expect it to be under 100 MA.

It sounds like you are already aware of the fact that circuits in a car will consume excess power immediately after the car is turned off. It can take up to 15 minutes, before the circuits go to sleep. Also if you are testing current consumption by randomly pulling out fuses and reinserting them, you will turn on whatever circuit you interrupted which only complicates the process.

This video starts by showing how to prepare the car prior to testing, to eliminate more common problems such as a stuck door switches, etc.. It then shows you how to measure voltages across each fuse to determine if excess current is traveling through that circuit. Your 1.8 amp draw should be easily detectable using this method.

if you happen to have a clamp on ammeter I would still monitor it while testing the fuses, just to make sure the problem hasn't cleared up on its own while you're doing the testing.

Once you locate the fuse carrying the excess current, that may be enough to determine the offending component, or you may still need to refer to a wiring diagram to see what components that fuse feeds.

 

Quick update on my parasitic drain testing:

I didn’t end up pulling the 40A fuse (#17 in the engine bay) for the trunk amp. Instead, I disconnected the amp’s power harness directly, and that brought the draw down further to about 0.80A.

These RDXs seem to enter sleep mode around the 10–15 minute mark, just like @RDX‑Rick mentioned. Even after waiting 90+ minutes, the draw is identical to what I see at the 15‑minute point. Hood latch is engaged and the immobilizer light is blinking, so the car is definitely “asleep.”

At this point the infotainment system looks very suspicious, and there are several modules I’ll need to start checking next — this is where I could really use some guidance.

One more detail I forgot earlier: right before the parasitic drain started, the infotainment system was acting up with “day/night” switching, “drive mode unavailable,” and “radio unavailable” messages. All FAKRA connectors were replaced back in 2022. I also noticed the USB port for Android Auto powering on even when the vehicle was locked and immobilizer active.

 

Update on my parasitic drain diagnosis for anyone familiar with the TCU (Telematics Control Unit) on the RDX. I might need some tips for those who have done a replacement.



I put all the audio fuses back in and reconnected the trunk amp, then unplugged the TCU harness to see what would happen. The car starts fine and the infotainment system still works—HD Radio, XM, Android Auto, and Nav are all functional. The only thing missing is hands‑free calling; Bluetooth connects, but the other party can’t hear me. Acuralink also shows no subscription info, and the app has been giving me “remote command failed,” which I hadn’t paid much attention to before.

Most important part: with the TCU unplugged, the parasitic draw dropped to 0.10A, which is a massive improvement.

I’m considering picking up a used TCU to confirm the diagnosis without spending too much. For now I can live without it, but it does mean no phone calls while driving.

 

Update: Resolved the parasitic drain after replacement of the Telematics Control Unit (TCU). I had purchased and installed a used unit from eBay that was pulled from a donor 2020 Acura RDX. I have referenced this article https://static.nhtsa.gov/odi/tsbs/20...04242-0002.pdf and confirmed I have the latest or slightly newer software versions -- until the last section where it stated that I have to go back to a dealership to reprogram the replacement TCU to the Keyless Access (Immobilizer) system via HDS tool.

It does makes sense as I noticed that even if I was able to resolve by parasitic drain I am failing to remote start my vehicle and perform locate. I am however, seeing the status of my vehicle, lock and unlock doors, lights, and honk are all working.