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sprinkles08, ASE Certified Technician
Category: Jeep
Satisfied Customers: 23004
Experience:  Chrysler/Dodge/Jeep Master Certified, ASE Master and Advanced Certified, Trans and Hybrid Specialist
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the BAS/ESP lights and the service engine light are illuminated

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the BAS/ESP lights and the service engine light are illuminated on my 8 cylinder 2006 grand cherokee. Whenever i take my foot off he gas or hit the breaks the car experiences a hard down shift that jerks the vehicle and slows down the vehicle. Any idea what would cause this problem?
Hello and welcome to JustAnswer!

Do you have a 4.7 engine? If so then you may have a bad throttle position sensor. If the TPS signal was off far enough in relation to the MAP sensor then it could cause the engine light along with the ESP and BAS lights, and it would also cause the harsh downshift because the trans controller uses the TPS input to control shift timing and firmness.

It's possible that the ESP and BAS lights aren't connected to the engine light at all also. There are many things that will turn these lights on including wheel speed sensors, dynamics sensor, steering angle sensor, brake pressure and pedal travel sensors, wiring, etc.

The first thing that will need to be done is see what fault codes have set. If you don't have a code reader or scan tool you can have the codes read for free at most large parts stores like Autozone. Once you know what codes are stored then the problem can be diagnosed from there.
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