2006 Maz3 2.3l Electrical issue
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Junior Member
Joined: Dec 2019
Posts: 1
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From: Kent, WA
2006 Maz3 2.3l Electrical issue
My Mazda 3 suddenly developed some sort of electrical short -
Symptoms:
- car parked outside ambient temp about 40 degrees
- started car, drove about 20 feet, all dash warning lights came on steady including headlights. Partial power steering, vehicle and brakes performing normally.
- drove car 2 minutes to a parking spot. Vehicle would shut off and also restart normally, but return to fault mode in 2 seconds or less
- voltmeter shows 17.3+ volts at the battery, belts intact
- decided to leave vehicle overnight (holiday) and tow later. Checked on it today while retrieving some items and the battery was completely dead.
- the transmission module was replaced 9 months ago, and is no longer located on the transmission to protect it from heat (just FYI)
- the engine took a little water from urban flooding a week ago (hit a deep puddle) shows no visible issues, however.
In the old days, I'd call this a stuck voltage regulator and replace the alternator, but I did not expect the battery to go dead with no key in the ignition. I understand that the PCM controls the alternator output by adjusting its internal volt regulator by reading on the internet.
My original plan called for unplugging the PCM feed and checking the alternator output, but the dead battery might complicate the issue. I'm looking for direction - does this information support a dead short in the battery (which seemed OK), a bad PCM, or bad alternator? Without input, my next step is to probably pull the alternator and bench test, while recharging the battery for a test later.
If you have knowledge please share [img]data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7[/img] The car ran very well until this sudden onset of an issue. Thanks everyone!
Symptoms:
- car parked outside ambient temp about 40 degrees
- started car, drove about 20 feet, all dash warning lights came on steady including headlights. Partial power steering, vehicle and brakes performing normally.
- drove car 2 minutes to a parking spot. Vehicle would shut off and also restart normally, but return to fault mode in 2 seconds or less
- voltmeter shows 17.3+ volts at the battery, belts intact
- decided to leave vehicle overnight (holiday) and tow later. Checked on it today while retrieving some items and the battery was completely dead.
- the transmission module was replaced 9 months ago, and is no longer located on the transmission to protect it from heat (just FYI)
- the engine took a little water from urban flooding a week ago (hit a deep puddle) shows no visible issues, however.
In the old days, I'd call this a stuck voltage regulator and replace the alternator, but I did not expect the battery to go dead with no key in the ignition. I understand that the PCM controls the alternator output by adjusting its internal volt regulator by reading on the internet.
My original plan called for unplugging the PCM feed and checking the alternator output, but the dead battery might complicate the issue. I'm looking for direction - does this information support a dead short in the battery (which seemed OK), a bad PCM, or bad alternator? Without input, my next step is to probably pull the alternator and bench test, while recharging the battery for a test later.
If you have knowledge please share [img]data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7[/img] The car ran very well until this sudden onset of an issue. Thanks everyone!
Member
Joined: Jan 2017
Posts: 64
Likes: 0
From: Greenwood, SC
Pull the battery and the alternator and bench test or load test both. You can use a local auto store for some tests. Don't test on the car, take them in separate.
Only after you try the step above, then try this next...
If they both load test fine, then re-charge battery and reinstall both, but pull all the fuses in the fuse box. Put the one in for the ECU and TCU and then let the car sit overnight. Check if battery is dead next day.
After that, you can add one fuse at a time and see which one draws the current from the battery by using a test light in series with the negative battery terminal.
My money is on bad battery or alternator though.
RGAZ
Only after you try the step above, then try this next...
If they both load test fine, then re-charge battery and reinstall both, but pull all the fuses in the fuse box. Put the one in for the ECU and TCU and then let the car sit overnight. Check if battery is dead next day.
After that, you can add one fuse at a time and see which one draws the current from the battery by using a test light in series with the negative battery terminal.
My money is on bad battery or alternator though.
RGAZ
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