2002 Jeep Liberty 3.7 - Jeep Garage - Jeep Forum

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Old 07-17-2016, 06:25 PM
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2002 Jeep Liberty 3.7

I have a 2002 Jeep Liberty Sport and as I was driving home last week all of a sudden all of my gauge lights came on and my gas gauge went for F to E and so I stopped cut the vehicle off and the gauge lights stayed on and the jeep wouldn't start so I unplugged the battery cable and plugged back up and the lights went out and it started up but now it's running really bad and brakes all but don't work now.. I replaced the spark plugs all 6, that didn't help so I replaced the map sensor and that didn't work, and last thing I've done is replaced the main computer and that didn't work. ***CAN ANYBODY HELP***


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  #2  
Old 07-18-2016, 07:10 PM
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Re: 2002 Jeep Liberty 3.7

Welcome to the garage.
Not familiar with the Liberty, but i presume that it also uses a PCI data bus, as the WJ does. Any component shorting out on this bus, can bring the bus voltage down and prohibit the engine from starting and light all the instrument lights. A shorted crank sensor is in many cases the problem on the WJ, but sometimes also water ingress in one of the connectors, causing corrosion and short in between the pins.
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Old 07-18-2016, 08:00 PM
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Originally Posted by Frango100 View Post
Welcome to the garage.
Not familiar with the Liberty, but i presume that it also uses a PCI data bus, as the WJ does. Any component shorting out on this bus, can bring the bus voltage down and prohibit the engine from starting and light all the instrument lights. A shorted crank sensor is in many cases the problem on the WJ, but sometimes also water ingress in one of the connectors, causing corrosion and short in between the pins.
Well the Libby uses the 3.7 in the sport and in that year ran on the jtec pcm. If anything I'd approach it like a 4.7. But I am curious if there are signs of water damage that would support something in the can bus shorted out
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Old 07-18-2016, 08:08 PM
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Originally Posted by ShawndShell View Post
I have a 2002 Jeep Liberty Sport and as I was driving home last week all of a sudden all of my gauge lights came on and my gas gauge went for F to E and so I stopped cut the vehicle off and the gauge lights stayed on and the jeep wouldn't start so I unplugged the battery cable and plugged back up and the lights went out and it started up but now it's running really bad and brakes all but don't work now.. I replaced the spark plugs all 6, that didn't help so I replaced the map sensor and that didn't work, and last thing I've done is replaced the main computer and that didn't work. ***CAN ANYBODY HELP***

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Has the jeep seen water? What I mean is things like mudding, river/stream crossings or just really deep puddles
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Old 07-19-2016, 09:42 PM
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Re: 2002 Jeep Liberty 3.7

No nothing more than the occasional rains


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Old 07-19-2016, 09:44 PM
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Re: 2002 Jeep Liberty 3.7

Also my brake pedal got really hard


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Old 07-19-2016, 10:44 PM
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Originally Posted by ShawndShell View Post
Also my brake pedal got really hard

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Makes sense. The jeep does have electrically assisted brakes. It's a secondary system that supplements the hydraulic brake system. So if your having a massive pci-bus failure they would be linked....

Did the brakes getting hard occur the same time as the other issues?

Just trying to piece the puzzle together
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Old 07-20-2016, 12:18 AM
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Re: 2002 Jeep Liberty 3.7

If the brake pedal becomes hard, it would be because the vacuum assistance is not working. With the engine off, there should normally be vacuum for three assisted brake applications. Can be that there is a leak in the vacuum side. I would first check if the vacuum hose from the inlet plenum to the vacuum booster isnīt disconnected.
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Old 07-20-2016, 06:51 PM
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Re: 2002 Jeep Liberty 3.7

Yes it all happened at the same time. Before that the brakes were fine


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Old 07-20-2016, 07:42 PM
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Originally Posted by ShawndShell View Post
Yes it all happened at the same time. Before that the brakes were fine

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Then I'd say what ever has plagued your electricals also effected the ABS/BAS systems as well as the electric brake assist uses the ABS modual
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Old 07-20-2016, 07:43 PM
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Old 07-22-2016, 12:03 AM
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Re: 2002 Jeep Liberty 3.7

I can be wrong, but the electric brake is a system which only works on the rear wheels and which uses the ABS sensors and valves to prevent rear wheel lock-up, as previously the mechanical proportioning valve did. Eventhough it can lower the rear wheel brake pressure, it will not make the brake pedal any harder to move. The only thing which would make the brake pedal hard is lack of vacuum to the brake booster. A loose vacuum line can cause bad idling and loss of the vacuum booster function, so i would check that out first. A complete failure of the ABS system can never cause the brake pedal to become hard, eventhough it can cause loss of brake pressure to the wheels.
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