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Robert R
Robert R, ASE Certified Technician
Category: Jeep
Satisfied Customers: 4517
Experience:  ASE Master Certified, Jeep Certified
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I have two issues. my 2007 jeep liberty has had all new

Customer Question

i have two issues. my 2007 jeep liberty has had all new spark plugs and all new coil packs yet at highway speeds the jeep starts to jerk as if it engine was misfiring. problem shows up after driving several miles. sometimes i get the feeling it may be transmission rather than engine.
JA: When was your transmission fluid last checked?
Customer: about 3000 miles ago during oil/filter change. there is no dipstick so i cant check it myself.
JA: Are you fixing your Liberty yourself? What have you tried so far?
Customer: only replacing plugs and coil packs
JA: Anything else you want the mechanic to know before I connect you?
Customer: another problem i have is cruise control suddenly shuts off and 3 brake related lights come on the dash. mechanic put scanner on iy and found no codes for either problem
Submitted: 6 months ago.
Category: Jeep
Expert:  Robert R replied 6 months ago.

Hello, welcome and thanks for asking your question. My name is*****'m a Certified Auto Technician with 29+ years experience. I will do my best to assist you. please keep in mind that I may need to ask questions of you before I can answer. When you reply please feel free to add as much detailed information as possible pertaining to your concern.

The first thing we need to do is find out about those 3 lights that are coming on...

Click the following link to view a representation of your instrument cluster --->> Click Here to view <<---

Let me know which lights (by number) are coming on and we can go from there....

Thank you,


Customer: replied 6 months ago.
31,9, dont see other listed
Expert:  Robert R replied 6 months ago.

Could it be 30?

Anytime these lights are illuminated it means that there is a problem in you ABS, Traction Control, and Electronic Stability Control and Brake Assist Systems. All of these systems have one thing in common and that is that they are all controlled by the ABS Control Module. If they are on it means that there IS codes stored on the ABS module. Unfortunately, a "Generic" scanner or code reader CANNOT access the ABS Controller. You will need to have it scanned with a compatible scanner, preferably the Factory Scan Tool WiTech System. Of course this narrows it down to visiting the dealer.

Cruise control is programmed to turn off any time there is a problem with the onboard computers. Since there are codes stored in the ABS this is why the Cruise Cuts out. As for the "Bucking" on the highway, If you are suspecting the transmission, it is definitely possible that the problem with the ABS is affecting the transmission. All these systems are interconnected meaning that one system uses information from another system for normal operation. For instance, the TCM (transmission controller) uses info from the ABS such as speed sensor data for proper shifting of the transmission. If there is bad data going over to the TCM, the transmission operation can be affected....

At this time, I recommend to take it somewhere that can scan the ABS Controller and obtain all the codes, better yet, if they can scan ALL onboard modules it would help even more. If you can post all of the codes retrieved here, I can either help you diagnose this yourself or I can give you a "Second Opinion" on the diagnosis that you receive from the shop...

Let me know either way how you plan on attacking this problem and I'll be happy to help....

Thank you,


Customer: replied 6 months ago.
it was 30
Expert:  Robert R replied 6 months ago.

Yeah, usually if one of those lights is on, all 3 nearly always come on together...

Keep me posted and let me know if you have any additional questions...

Thank you,



If you need additional information, don't hesitate to ask, I am happy to help as long as necessary to help solve your concern. Remember, a "Positive" Rating will not close this question, You can post a reply here whenever you want, even after rating my answer! .