Monday, January 21, 2013

2002 Jeep Liberty: Check Engine Light On Dash, Low Fuel Mileage and RPM bit High then Normal

OBD Code P0740 On Jeep Liberty

These Error code gets set when the torque converter clutch either slips or doesn't apply at all when it is commanded to operate.
And issue with  torque converter can definitely cause the issues which you have mentioned and noticed while driving.

As per your vehicle details mentioned the torque converter is located between the engine and trans and is what transmits power from the engine. In the front of  torque converter assembly  is a disc clutch that is turned on at times to give a mechanical lock between the engine and trans to raise fuel mileage slightly. 

There are a few causes for this code. Since there isn't a dedicated torque converter solenoid  on your vehicle model like some transmissions have so  you can rule out a solenoid issue. 
On your vehicle the converter clutch is applied by the same solenoid as another clutch, along with a valve in the valve body. If you aren't setting a code for the solenoid switch valve (P1775) then you can also rule out a valve body problem.

So now on your case i will say then other possibilities can be :-----
Leaking seals on the transmission input shaft, where the converter is fed the fluid it needs to operate. This would be an internal leak, not something you would see on the ground.

Or the other possibility can be worn or incorrect fluid or a fluid additive. Get the fluid quality and type rechecked.
Any of these will cause the converter clutch to slip as it engages and in some cases could cause the code to set.

The most common cause of this would be the torque converter itself. If there is no debris from the failed converter scattered throughout the trans then replacing the converter itself will usually repair it.
But  if the converter is in very dirty and worn out condition , and replacing converter is not solving the problem completely  then a complete trans overhaul by the shop is advisable.

The repair cost may depend on what kind of  repair job is carried on your vehicle.Only torque converter replacing or complete trans overhaul. But if in case you avoid the repair at present and wait for some more time then in that case ,it's very much possible that you could drive it indefinitely without problems if you don't repair it. As long as the converter clutch isn't delaminating and scattering debris throughout the trans then the only symptoms you would have is the engine light, slightly lower fuel mileage, and slightly higher cruising RPM's. 

But if you need my advise and suggestion on these issue then i suggest you to get the  trans pan drop service rather than a flush. This will allow you to see inside the trans and see whether or not there is debris coming from the converter, and will also allow for both filters to be replaced. Make sure that only ATF+4 is used and no additives are put in the fluid when the service is done. If there is no clutch material in the pan then you can probably drive it indefinitely without repairing it.Till the serious seen problem arise.

But if there is no cash issue then dont wait for major problem to arise, take your time and get the trans inspected by profession transmission repair overhaul shop and they will suggest you further about what repair or replacement is required.

These details will help.

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