AX4N-Limp Mode/FMEM....2nd gear only

[nik97]

My transaxle has gone into Limp mode and I only have second gear. I can disconnect the battery erasing KAM and it will shift normally for about 20 minutes or one key on cycle. Once I drive it again, I get 2nd only. Anyone experienced this?

 

[Axianator]

Just a few quick Q's:

- by what means have you confirmed that the EEC is running in limp mode?
- have you installed an aftermarket chip or flash tuning device on your EEC?
- have you double-checked the primary wiring harness atop the transmission?
- have you double-checked the EEC's connection to it's 104-pin wiring harness?

 

[Mr Anonymous]

Replace the MLP sensor.

 

[nik97]

I would have to say that I believe it is in limp mode. There is no way at this time I can really confirm it. However, Ford's Failure mode strategy programming takes effect when there is a loss of a certain input(s). This strategy is usually second gear only depending on the vehicle. The reason I believe it is in limp mode is because, like I said, I can erase the KAM and drive around without ant problems. As soon as I cycle the key, I will end up with only second within a few minutes of driving. FMEM will usually not take effect if a fault is detected only one(one drive cycle). If the same fault is detected again within 80 key cycles(think it's 80) then the failure mode stategy will be employed.
Yes, I do have an Xcal1 from FPS including a shift shedule and firmness program. One of the first things I did was reflash the factory format. The problem was still exactly the same but it is still a possible cause. I dont think that the SCT's EEPROM tuning has the ability to interfere with Fords OBDII monitors and RAM.
All of the Harness conections are good. I cleaned the connecteor to the trans and inspected the rest of the harness for visible tears and pssible concerns.

Chris,...MLP..Manual lever position?..or TRS....are we talking about the same thing? If so, I'm not sure that is the problem. After I disconnect the battery, I can drive without a problem..even manually through all the gears. This is wierd too...even after I have only second gear, I can manually put it in first to start and slowly go through all the gears manually including 4th-TCC lockup as long as I maintain a constant or increasing trottle posistion...as soon as I let off just a hair, even @60mph...it dowshifts to second and stays there. Another reason I belive this is limp mode is that when in second, I can accelerate then, when I let off, it goes into neutral untill I give it enough throttle to gradually meet the engine speed of 2nd gear at that speed.

 

[Mr Anonymous]

MLP, TRS, whatever you call it it's the same thing.

Yup, a bad one will work, overheat, trip limp mode, etc. And clearing the keep-alive will bring it back for a bit, until it flips it again. Been there, done that.

 

[Axianator]

FMEM will usually not take effect if a fault is detected only one(one drive cycle). If the same fault is detected again within 80 key cycles(think it's 80) then the failure mode stategy will be employed.

Actually, on most EEC-V strategies, FMEM modules and/or background executives are called once per background loop (which, depending on the strategy and the processor, can be up to several hundred times a second). FMEM can also be activated at any point during EEC operation, regardless of the current operating state (KOEO or KOER).

I dont think that the SCT's EEPROM tuning has the ability to interfere with Fords OBDII monitors and RAM.

Correct.

Chris,...MLP..Manual lever position?..or TRS....are we talking about the same thing?

As Chris has noted, the MLPS and TRS are one in the same to the factory engineers.

Given typical Gen 3 SHO FMEM operation, I also have to agree with his diagnosis re: your TRS.