Been driving the Buick around and the SES lit up. It was the DTC P0121 Throttle Position (TP) Sensor Performance error code. I found Danthur’* post https://www.gmforum.com/obd-ii-troub...9/#post1390955 I installed a new AC Delco one and it is amazing what a difference that made. The throttle response is now significantly faster and smoother. Thanks to Danthur for posting that fix! When the TPS is acting up it really can show a lot of different symptoms. I was getting intermittent hesitation/stumble on acceleration but until the SES lit up I really had no idea where to look.

Glad you found Dan'* writeup helpful!

I betcha if you had scanned for codes you probably would have found a PENDING P0121. Even though your CEL was not illuminated, the code would still be in the PCM. Each P-code has a specific rule for it. Some will trip the CEL light the first time the PCM sees an error and others will trip 3 times before the PCM will trip the light.

With today'* newer cars and complex sensors, I cannot stress enough to people to at LEAST purchase a $50 pocket scanner. It saves you trips to Autozone to have them scan etc.

Thanks for the info. I never considered using a scanner before the ses light went on.

Digging this thread up. But yes!
get a $20.00 blue tooth dongle from Amazon and $5.00 for Torque Pro app.

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