# 2000 Sentra Auto Transmission problem and TCM question



## robbiewilso (Jun 14, 2018)

This car I recently bought with a few minor issues but the transmission seemed ok, shifted normally, had good power on acceleration, overdrive could be turned off and on, etc. Now the OD light won't come on, and the car seems to be pretty well stuck in limp mode. No matter what gear I select i won't downshift or upshift. Transmission fluid is pink and doesn't smell burned. I am able to connect an OBD reader to the port and read check engine codes which the only one I have is P1140 which I believe to be caused by a defective intake camshaft sensor which only really affects advancing the timing. I have tried in vain to get the OD light to respond to the button on the side of the gear selector. I have also tried getting the diagnostic mode to come on as detailed in the FSM but I have not had any success at all due to the fact that the OD light won't come on anymore. I know where the ECM is (passenger firewall) but I guess I am begging for help and experiences from others who have run into this issue. The fact that I can't get the OD light on means there is a broken wire or a broken control module I am guessing? Just any advice please from people who I'm sure have more experience that I do. Thanks so much!


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## rogoman (Dec 16, 2004)

A weak battery or low battery voltage can cause the transmission to enter into fail safe mode. This will cause a loss of power because the transmission will be locked in a particular gear. A properly working charging system puts out about 13.2 to 15.0 volts, but this is a general spec. and the factory service manual should be referenced for the correct charging system voltage specifications for a particular vehicle. A battery should have a static charge of 12.2-12.6 volts. If a battery is not good, the charging system may not be able to charge properly. Also check all the engine/transmission grounds.


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## robbiewilso (Jun 14, 2018)

I did have an auto parts store check the battery and the alternator and they checked fine. I will look at all the wiring and grounds as well. I HAVE had the alternator light come on that's what had me testing the alternator; it may be an intermittent failure but it hasn't come back on since. Of course I haven't been driving it except for testing because I don't want to damage the transmission


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## Tonyt22 (Jun 24, 2018)

I'm not a expert on nissans but I have worked on alot of cars your battery may show that it's good but still be weak enough to drain the rest of the charging system that is a common problem I've seen on plenty of auto vehicles I would suggest find a battery house and pick one up for 50 bucks or so to try it out


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## robbiewilso (Jun 14, 2018)

Thanks Tonyt22! I have a new battery in a different car and I am going to swap them just as a test.


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## robbiewilso (Jun 14, 2018)

Well the battery swap didn't do anything. I suppose I will try to find a cheap used TCM/ECU to swap. Thanks for the help!'


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