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Battery Light + Brake Light Combo! And recently + Oil Light For A Triple Combo!

317 Views 1 Reply 2 Participants Last post by  GTSDriver2003
Hello again everyone,

The car: 2002 Mitsubishi Eclipse GS Automatic 190,000+ miles.

Most recent jobs:
This month: Cleaned Mass Airflow Sensor nearest air filter box with MAF cleaner
This month: Cleaned carbon soot inside Throttle Body flapper valve with carb cleaner
This month: Cleaned carbon from Idle Air Control Valve with carb cleaner then let air dry and reinstalled
1 month ago I did a basic oil change with replacement oil filter. 4.5 quarts fresh oil
2 months ago I did a timing belt job

The problem:
Car starts right up every time. Idles naturally around 800 RPM. But recently, when coming to a stop or at a red light the car will sometimes idle below 500 RPM/shudder/and almost feel like it wants to turn off. When this happens the Battery Light and Brake Light will both come on together. It doesn't happen consistently though. There are some days my family member drives this car and doesn't experience anything at all. I've read that it may be a loose alternator belt, bad alternator, blown fuse, loose battery connection on the terminals, or Big-3 wiring.

I have the car in my garage for the weekend to check out. This week I pulled out my scan tool to test the battery and the battery is good. I tested the alternator with my scan tool via turning on the headlights and staying at 2,000 RPM for a bit until the scanner prompted to stop. Scan tool says 14.31V so the alternator is still good and within spec. I drove the car around the neighborhood block with my scan tool plugged in to attempt to replicate the issue and I couldn't. But I did see the RPM drop slightly at a stop sign (no battery and no brake light) but then it went back to normal idle. Since this was the closest I got to replicating the issue I scanned the car again but this time with Mitsubishi OEM Enhanced. I finally get a code and it is related to the transmission? Code = 8A. I then try to read codes normally and I get a communication error. I turned off the car, unplugged the scanner, checked my OBDII connection, plugged the scanner back in and it connects properly. No freeze frame trouble codes.

When the key is in the ON position I see the battery light, brake light, & now oil light triple combo.

Any ideas?

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There is a plug in besides the fuse block on the driver side fender. It can become loose and cause this. Also, check all wiring on the pigtail into the alternator. It is subjected to a lot of heat and becomes brittle. I had to soldier a new one into my wiring harness mine was so bad.
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