Service light on

[LocoMangoV6]

The service light is on and i took the car to get it scanned but no codes founds. What else could this be. Also a old code was found for the downstream o2 sensor but the guy said is was in the history side of the ecu. If any one can help or point me in the right direction i will appreciate it. Car is galant 3.0 v6 2000

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[oddball]

Shot in the dark but I have an 03 V6 and the SES would come on in spurts when I'd drive long distances. Sometimes it'd turn off after some city driving, presumably from the sensor's responsiveness or wiring fading with old age. The code I originally got was P0139 which is basically sayin it's on it's way out. I swapped the sensor and disconnected the battery for ~30 mins and haven't had problems since.

Maybe yours is having the same issue but when you went in to have it checked it was on a "city driving phase" but the light hadn't turned off yet.

Could be way off but it never hurts to change an old 02 sensor, if you can spare the $45.


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[oakrdrs187]

Its probably a bad O2 sensor. My advice, disconnect the battery for at least 10 minutes. Reconnect and drive the car normally, see if the light comes back on.

[LocoMangoV6]

Ok thanks guys I'll check for the o2 .

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[johnygezony]

I have a P0139 as well, Bank 1 sensor 2, So i am confused as to which one that actually is. My guess thus far is the bank closest to the firewall, and not the first sensor highest up. That being said, I haven't been under the car, where is that darn thing?

[oddball]

Ha, I had the hardest time identifying too. The service manual refers to them as right/left bank and front/rear sensors instead of numerically, so to me it's a little unclear. But page 13B-141 (and the next 2 pages) are the diagnostic pages for code P0139 and it points to B1S2 as the downstream sensor (after the cat) on the bank nearest the rear of the car. However, I saw someone on a galant forum somewhere identify the banks the opposite way. Double however, I changed B2S2 thinking it was B1S2 and the SES light came back on after a few days. So before you go through all that lemme change the sensor according to the manual and see if it solves the problem.

[oakrdrs187]

Bank 1 and 2. Stand in front of the motor, the front where the crank pulley is. Left side is 1 and right side is 2.

[oddball]

Switched it, light went off without disconnecting the battery, so I'll assume all is well.

Btw this sensor in particular was an absolute pain, took like 2 hours to find the right combo of tools to get the right placement and enough torque to get it off and then back on (prob just a V6 problem). Lemme know if you get stuck or want tips before you get stuck.


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[LocoMangoV6]

That happened to me too the light went off and came back on a couple of miles latter. My friend at work do part time at a shop he said he will double check for me because is weird for that to happen.

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