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Eric
Eric, Automotive Repair Shop Manager
Category: Jeep
Satisfied Customers: 29976
Experience:  20+ yrs. experience as repair shop manager and technician.
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P0068 code, Yes, 2005 grand cherokee 4.7, Yes. Changed map

Customer Question

P0068 code
JA: Just to clarify, what's the exact code? And have you tried to reset it?
Customer: Yes
JA: What is the model/year of your Jeep?
Customer: 2005 grand cherokee 4.7
JA: Are you fixing your Grand Cherokee yourself? What have you tried so far?
Customer: Yes. Changed map sensor, changed plugs, checked for fuel in fuel rails, cleaned throttle plate
JA: Anything else you want the mechanic to know before I connect you?
Customer: Ran perfectly fine then out of nowhere this happened. Rough idle, hesitant to start, shuts off and over heats
Submitted: 3 months ago.
Category: Jeep
Expert:  Eric replied 3 months ago.

HI,

P0068-MANIFOLD PRESSURE/THROTTLE POSITION CORRELATION

POSSIBLE CAUSES -

Vacuum leak - Resistance in the (F856) '

5-volt supply circuit - (F856)

5-volt supply circuit shorted to ground - Resistance in the (K1) map signal circuit -

(K1) Map signal circuit shorted to ground - Resistance in the (F855)

5-volt supply circuit - (F855)

5-volt supply circuit shorted to ground - Resistance in the (K22) TP sensor No.1 signal circuit -

(K22) TP Sensor No.1 Signal Circuit Shorted To Ground - Resistance in the (K900) sensor ground circuit -

Map sensor -

Throttle position sensor -

PCM

As you can see, there are quite a few possible causes. To test to determine the cause, a scan tool with testing and live data function capabilities is needed, as well as a voltmeter.

If you have these, let me know and I can upload the testing directions

Customer: replied 3 months ago.
I have a scan tool and meter...I have replaced the map sensor today and cleaned throttle plate and tired to find a vacuum leak but didn't see one. Replaced air filter and plugs
Expert:  Eric replied 3 months ago.

HI,

Ok, I have attached the testing directions which include pinouts and wiring schematic.

Not sure how you tested for vacuum leaks, but if you dont have a smoke machine, then the best way is with a can of carb cleaner. with engine idling, spray each vacuum hose, air intake tube, throttle body, pcv valve hose and base of intake one at a time and if idle change when one is sprayed, replace the culprit

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Expert:  Eric replied 3 months ago.

I noticed we have not yet resolved your concern you asked about. I would sure appreciate it if you would reply so I can offer my skills and knowledge and repair guide access to help as best I can.

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Customer: replied 3 months ago.
I have now changed the map sensor, plugs, throttle position sensor. I can't find a vacuum leak with carb cleaner. Still will hesitate and shut itself off. Short term fuel trim is from -11 to sometimes -30%.
Expert:  Eric replied 3 months ago.

Hi,

Did the MAP and TP sensor wiring check as good?

Customer: replied 3 months ago.
It looked pretty good. I looked for any open wires
Expert:  Eric replied 3 months ago.

HI,

Ok, you will need to test them as the testing directions provide for. If you are 100% positive that there are no vacuum leaks and wiring is good, then that means the pcm is faulty.

Customer: replied 3 months ago.
Finally took it to the shop they think blown head gasket...no vacuum leaks everything testing good...running hot and white smoke now when you crank it
Expert:  Eric replied 3 months ago.

HI,

Ok. would not have suspected that

Customer: replied 3 months ago.
Me either!! Especially when I kept throwing money Into parts
Expert:  Eric replied 3 months ago.

HI,

Well, if you decide you want to tackle this job, I can help you with that, but it is a pretty big job

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