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Check Engine Light and Transmission

I have a 2005 Suzuki Aerio with an automatic transmission. Occasionally, maybe once every month or two, the check engine light will come on while I am driving and the car will immediately stop down-shifting from 3rd gear. The car otherwise seems to run fine but I end up having to manually shift to get to wherever I am going. Then on my next trip, the transmission will shift fine but the check engine light will stay on for an additional trip or two and then go off.

I have no idea what is going on. Help! I have not had anyone look at it because by the time I get to it the light is off again and the car seems to function fine.

The light means that the car knows exactly where to start in diagnosis. There are error codes stored in the computer. Many chain-type auto parts stores will read these codes for free. The next time the light is on, get to one, have them pull the codes, write down the exact code (e.g. “P1234”) and post it.

If the light isn’t on, some code readers will also read “history” codes. Some auto parts stores might have code readers with that kind of capability, but this often means you need to pay a shop with better equipment to read them. All you need to do is ask: “can your code reader pull history codes?”

In any case, there is no point in guessing. You need to know the code(s).

However, at the very least check your transmission fluid immediately - follow the procedure as outlined in the owner’s manual. Its nothing like checking the oil.

The trouble codes will be stored in the computer regardless if the light is on or off…Transmission codes are different than engine codes and may require a more sophisticated scanner to read them…

The codes will be stored - but trust me, I’ve been there. Most of the low end scanners won’t read them unless they are current codes (engine light on). The AP lackeys in my area won’t step foot out from behind the counter unless you assure them that the light is actually glowing. Thus one does need a scanner that will do history codes. I might just be unlucky with the morons in my area.

There are also plenty of transmission codes in the generic list (P07xx-P0899) which do trigger the check engine light & will be read by generic code scanners. The OP probably has at least some of these (unless it is a transmission input issue such as a TPS).

But then, yes. Unfortunately there are those manufacturer specific codes that won’t light it up & won’t be read by generic scanners. Drives me nuts.

That CEL (check engine light) is just a kid in class waving her hand trying to get you attention because she has the answer. You need to have the codes read. Some places will read them for FREE. Try Autozone or Advanced Auto Parts. Get the exact code (like P0123) not just their translation into English and post it back here.