Car shudders/check engine light comes on post computer update

So last week, I took my car ('09 Matrix, 75K miles, bought new) in to the dealer because there was a recall out on the computer - apparently it would still gun the engine if you were to push both the brake and gas pedals at the same time. The fix was a software patch that would prevent that from happening.

Anyway, I get the car back and it starts shaking for about 2 minutes, whether it was idling or moving. I didn’t think much of it because it went away and nothing happened for about a week. Sunday, the car shudders for a few seconds and the check engine light comes on. I check online and it says that for an '09 Matrix, the most common cause is the gas cap not being tightened all the way. I give it a shot, and voila, it goes away for 2 days. Yesterday, the shudders for about 20 seconds (it starts when idling, but continued for a few seconds after I started moving), and the check engine light came on. This time, fiddling the gas cap didn’t cause it go away.

When I had the car in for the recall, they did the whole “free 25-point inspection” bit and the only item of note was that the transmission fluid was starting to change color. My car hasn’t ever had to have any maintenance work done on it (besides the standard service interval).

So I guess my main question is: what’s the cause of this happening, and was it related to the recall fix?

Also, side question: when they said that the transmission fluid was changing color, they also said that my car required a full flush (for only $400+ dollars). Normally I’d be skeptical, but this was a Toyota dealership service department. Are they BS-ing me?

They messed up! Go back to the dealer and talk to the service manager about it.A transmission fluid flush is not recommended by Toyota.A simple drain and fill is safer for your transmission and cost around $70. A transmission fluid change including the removal of the pan and the replacement of the filter.and gasket should cost you around $200.

When that “check engine” light came on…you should have had the codes read.

If the light is still on, get the codes read and post the results here.


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Good advice above. One explanation for the idle shuddering might be that your Matrix needs to re-learn its optimal operating parameters. It may have lost that data during the reprogramming to fix the other problem. The engine computer is constantly adjusting the operating parameters as the various parts inside the engine become coated with carbon, oil etc . That’s normal, occurs w/age and miles driven. That’s done to keep the idle nice and smooth without needing periodic tune-ups at the shop. But the downside is that if that data is lost, it has to be re-learned again. In the meantime the idle quality may suffer. The dealership should be able to determine if this is the cause or not by examining the stored diagnostic codes.

It is possible that something was knocked loose while checking the air filter but without checking over the engine and knowing the fault code it is impossible to place blame.

A transmission service for $200 won’t happen at a dealer. The filter costs $94, sealer $16, transmission fluid is $10 per quart (5). The labor is 1.3 hours.

Yep! my Toyota dealer is asking $300 for this service.

Wixx filter/gasket is $13 at rock auto. Drop pan, change filter, add new fluid.

Maybe the OP is not able to do this service by himself thats why he goes to the stealership.

true. but the dealer cost of $94 for filter just caught my attention. when RA has $8 filters too. i just bought toyo T-IVa fluid for $6qt at dealer