Upon purchasing a 2015 Highlander from a dealership, the vehicle failed to start after a day or two of inactivity. Upon closer inspection, the owner discovered a tracking device securely attached to the radiator fan wiring harness with zip ties.

Uncovering Battery Drain Issues: A Guide to Parasitic Draw Tests

Parasitic draw, the slow drain of a vehicle's battery caused by devices drawing power even when the engine is off, can be a common issue for car owners. Here's a simple guide on how to perform a parasitic draw test to identify the culprit.

Preparing for the Test

Before you begin, ensure your vehicle is fully charged or has a healthy battery. Open the hood, remove the keys and fob, close the doors, and lock the car. Allow the vehicle to sit for 30-45 minutes so all modules go to sleep.

You'll need a digital multimeter with DC amps and mA ranges, a small wrench for the battery terminal, a short 10- to 12-gauge jumper wire or booster cable, a fuse puller, and a notepad/phone to record readings.

Baseline Draw

The first step is to perform the baseline draw. This is done without the Progressive Dongle or any other OBD2 devices. Loosen and lift off the negative cable clamp from the battery post. Set the meter to DC Amps, connect it in series, and record the steady mA reading. This reading is known as the Baseline mA.

The Test with the Progressive Dongle

Insert the Progressive Dongle, wait for it to enter sleep mode, record the steady mA reading as With Dongle mA. Subtract the Baseline mA from the With Dongle mA to find the Dongle's added draw.

Interpreting the Results

If the reading is ≤ 60-75 mA, it's usually fine for daily driving.
If the reading is 75-100 mA, it may cause issues if the car is parked for several days.
If the reading is > 100 mA, it's likely to drain a battery quickly.
A reading of > 150 mA is likely to drain a battery quickly.

Normal Sleeping Vehicle

A normal sleeping vehicle (without a dongle) typically draws ~20-50 mA.

Safety Precautions

Always remember to work on the negative (-) battery cable for safety, never start the car or turn on high-current loads while the meter is in the amps mode and wired in series, and keep doors closed and dome lights off.

Conclusion

By running a simple parasitic draw test, you can find out exactly what's leeching your battery life-and decide whether it's worth keeping. Mechanics often recommend unplugging unnecessary OBD2 devices, especially in used cars where hidden trackers may already exist. Insurance companies like Progressive, Allstate, and State Farm use GPS-tracking devices connected to the OBD2 port in new or used cars, which can sometimes cause battery drain issues.

Upon purchasing a 2015 Highlander from a dealership, the vehicle failed to start after a day or two of inactivity. Upon closer inspection, the owner discovered a tracking device securely attached to the radiator fan wiring harness with zip ties.