Tricking the PCM... need info

[Sorry]

Hey guys. I came up with a crazy idea. I'm not sure if it will work or not. But if the sensors work as I'm hoping, it should work just fine.

I'm having a P0741 TCC unlocking issue that I've pretty much narrowed down to being my actual TCC. Solenoid seems fine. Resistance is in spec. TCC locks, but unlocks from slipping.

This code is thrown when one of two conditions is met. Each condition requires two criteria. 1) solenoid is unlocked and engine rpm = turbine output speed or 2 solenoid is locked and rpm>tos.

Does anyone know if the turbine speed sensor works the same way the crank sensor works. For instance, at 3000 rpm, are the crank sensor and the TSS sending the same signal? Are they just both 50hz (or any correlated signal)? Or are they different types of signals that the PCM would sort out?

From my understanding, they are both magnetic pulse senders.

My thought is... have the TCC Solenoid signal to power a relay that would switch between Crank Sensor and Turbine Speed Sensor. When the solenoid is not hot, TSS would be sent to the PCM as normal. But when the solenoid is powered, the relay would send crank sensor info to the PCM to make it think that the TSS is matching the rpm.

I know... it's not the right way. But I'm going to drive this transmission until it leaves me on the side of the road. I'm just trying to avoid tripping the OD Off light, which puts the PCM onto limp mode. I can deal with the few MPG of not having the TCC lock. I can't deal with a limping PCM

 

[imp]

Hey guys. I came up with a crazy idea. I'm not sure if it will work or not. But if the sensors work as I'm hoping, it should work just fine.

I'm having a P0741 TCC unlocking issue that I've pretty much narrowed down to being my actual TCC. Solenoid seems fine. Resistance is in spec. TCC locks, but unlocks from slipping.

This code is thrown when one of two conditions is met. Each condition requires two criteria. 1) solenoid is unlocked and engine rpm = turbine output speed or 2 solenoid is locked and rpm>tos.

Does anyone know if the turbine speed sensor works the same way the crank sensor works. For instance, at 3000 rpm, are the crank sensor and the TSS sending the same signal? Are they just both 50hz (or any correlated signal)? Or are they different types of signals that the PCM would sort out?

From my understanding, they are both magnetic pulse senders.

My thought is... have the TCC Solenoid signal to power a relay that would switch between Crank Sensor and Turbine Speed Sensor. When the solenoid is not hot, TSS would be sent to the PCM as normal. But when the solenoid is powered, the relay would send crank sensor info to the PCM to make it think that the TSS is matching the rpm.

I know... it's not the right way. But I'm going to drive this transmission until it leaves me on the side of the road. I'm just trying to avoid tripping the OD Off light, which puts the PCM onto limp mode. I can deal with the few MPG of not having the TCC lock. I can't deal with a limping PCM

Have you gone into limp mode yet? 3rd. gens. flash 4X4 HIGH when PENDING limp mode, WRENCH on when confirmed. Can't for sure say about 2nd. gen, sorry. It sounds as though your TCC is "mechanically/hydraulically challenged rather than an electrical issue. If so, yer spinnin' yer wheels with electrical modifications, IMO. In my 3rd. gen., I got OD OFF flashing, TCC Solenoid Failure, TCC was not engaged, drove it 2,000 miles back home with no TCC engagement, hardly noticed change in fuel economy. Replaced solenoid module, trouble gone.

As far as tricking the PCM, been there, tried that, no work. Unless you are capable of reprogramming the PCM, it's program will usually detect outside attempts at inputting any signal or otherwise disrupting it's scanned program.

I could be wrong, given the designers' moonlight madness when programming the PCM, but it just doesn't seem likely that they would throw a limp mode for a non-operating TCC. At least 3rd. gen doesn't. imp

 

[Sorry]

I guess it might not necessarily be limp mode. It's just the OD off light flashing and experiencing slightly harder shifts.

It's an 02, by the way.

I think if I tried it, worst case, it just doesn't work and I undo it. Best case, it tricks the pcm and the OD light goes off