QuestionI have a 94 Chrysler LeBaron Convertible with a 3.0 V6. When we start the car up and first drive it, it works fine. Eventually it shifts into second gear and stays there. After it is turned off and sits a while it will shift fine. I just replaced all the motor mounts as 2 were broken (I just bought it.)It was doing this before the motor mounts were replaced. What can cause this? Somebody suggested a sensor?
AnswerHi Steve,
This behavior is known as "limp-on mode" and it can be caused by several different malfunctions so there is no single reason I can give you. It may be a sensor (input or output speed sensor) but trying that without further diagnosis is not practical.
That exact lock up is what happens when the transmission computer notices something is wrong and so it protects the transmission by only driving in 2nd gear until it can be serviced so as to protect against any further damage. It is called "limp-in mode".
There is a possibility there is some internal mechanical wear/damage to the internal clutches of the transmission, but because the cost of rebuilding is so high it is worth spending a little on analyzing whether that is true or not. It may also be the case that the problem is with electrical connections/computer or with the transmission fluid system (hydraulic) and those can be repaired without removing or rebuilding the transmission at much less cost.
The transmission has an electronic controller that has the ability to recognize malfunctions and store them in its memory as two-digit fault codes. An electronic readout device is plugged into a port under the dash to access the memory and tell you the fault code numbers. It would be worth spending about $50 to have this done just in case the problem had to do with the hydraulic or electronic parts rather than the internal mechanical parts because those could be repaired without taking the trans out of the car and dismantling it. So a dealer or a competent independent transmission shop (but NOT a franchise type like Aamco where the usual answer will be to do a "rebuild") with a reader for Chrysler transmissions should be able to do that. Ask for the code number(s), what they mean, what repair is needed and how much it will cost. Be sure that they have the 6-pin ("bus diagnostic connector") reader plug adapter that will give them access to the memory via the port under the dash. This is NOT the same plug as is in the engine compartment (which is a different-shaped 6-pin plug) for accessing the engine controller memory. Their reader also has to be equipped with a program (cartridge) that accesses the transmission computer. A Chrysler dealer will have this device called a DRB II.
Then write back and we'll evaluate what you were told, particularly what are the fault code numbers. I have the '94 factory repair manual and can look up what the numbers mean and what needs to be done to fix this.
You don't have to authorize a repair until you decide you understand the situation, and maybe get another repair estimate. You might even ask before they do the readout if in the case you decide to authorize the shop to do the repair "will the cost of the readout be credited against the cost of the repair"?
So take your time with this so you don't do any more unnecessary repairs. The cost of a rebuild is high so getting a second bid is worthwhile and also comparing warranty provisions is wise.
But that readout is the only way to avoid doing the wrong repair.
Roland
