off and on SES
 

I have a 2002 SC1, after failing to make my odb scanner to work, I took it to autozone.. where the SES light reads p0732 p0733 p0734 so I know it's gear 2, 3, and 4. After driving it awhile all the sudden SES light goes off... I take it back.. no codes... anyone have a thought to whether, or not I need to take it in and break the bank with tranny issues? Any advice for something to check or do to eliminate the issue? I got this car used with 137K on it. All I have done is tires, alignment, replaced coolant fan motor (died causing overheating) and plugs.

Why don't you try changing the transmission fluid and filter first? If it's never been done, it's probably way overdue.

Do you have and after market alternator? If so check the output voltage. I once on a 93 had about 16 volts output and it was screwing up the auto trans.

OP is banned so he's not likely to respond.

16V? wow, that was one cheap voltage regulator in there.

I always thought the charging system light would go on in overvoltage as well as undervoltage conditions.

Anyone know if this is true on Saturns (S, L, Ion)? Never gave it a thought all these years.

This is exactly why we like fresh active folks to join and post---always something new or from a different angle.....

Yes , actually the transmission shop found the problem, it was starting out in 2nd gear. After they replaced the alt, all was fine.

well then--a tranny shop worth something AND hones. Never been to one that didn't try to rip me off. One of the many reasons I hate automatic transmissions. They have too many moving parts, they break more easily than manuals, and when they do you're looking at a min $500 in labor just to take it apart and put it back together as part of the repair. Plus the cost of the repair---100% markup on parts, labor costs. At last $1K in many situations if it is not just a simple adjustment.

Now with these 6,7,8 speed automatics, smoother ride, but more to break.......

Hey Derf, to answer your question, it all depends if the voltage regulator is inside the alternator, or controlled by the PCM. In the vehicle mentioned, it's too old to be controlled by the PCM, so only a low voltage light will come on. At 16 volts, the PCM shuts down, trans will fail safe and codes gone when PCM shuts down, but eng. will still operate in open loop. Must have been able to pull codes before shut down at some point.
Vehicles with PCM controlled regulators will set U codes for quad driver failure if under or overcharging, and will turn on MIL. PCM will have to be replaced, and re-flashed to that vehicles VIN. Low battery light will still come on if the alternator is unable to produce the voltage demanded by the PCM, will store a code, and will shut down non essential devices, like blower motor, A/C and sometimes the radio too. I have also seen it turn on ABS, traction and stability control lights due to voltage drops as well, not shutting them down necessarily, but setting low supply voltage codes.

Thanks!

My saturn with the 16v trans issues was a 93 model sl2.

You're welcome Derf.