Trans Program after a motor + transmission swap

[Nrick]

Hey guys,

The car in question is a 05/1994 production 1995 540iA (ASC+T) using a donor 10/1993 prod. 1994 540iA(NO ASC+T). I have used the M60B40, ZF5HP30(rebuilt about 3k miles ago), the DME, and the wiring harness from the donor car. The car does not have ASC+T anymore.

I've searched the forums but none of the threads are related to what I am experiencing. I don't know what triggers the problem but the car can have trouble starting and displays the Trans Program error when it does not start. After a few more attempts at starting the car, it usually starts then idles at 1000, surges to 1500, and drops back down to around 500. Once it starts, it will start fine any attempt immediately after. I have drove it and it usually drives fine, but two notable incidents have happened. I have had the car stutter or jerk once and recover while driving highway speeds of 65mph. The other time the car stalled/shut off and displayed the trans program error while I was idle/stopped at a stop light.

EDIT: The Trans Program error is not displayed when the car finally starts and the car does NOT go into limp mode.

The only thing I have done so far is check the Idle Control valve and it checked out fine. I purchased the battery in mid 2015, but I plan to check the voltage on it when I can. I also plan to check on the DME and Fuel Pump relays, and the transmission control module.

I am hoping to hear out some more suggestions or your experiences.

[whiskychaser]

Sounds a lot like low voltage rather than an issue with the trans or TCM. It would also account for the difficulty starting and the car stalling. A close inspection of the battery/charging system may be in order. Meanwhile, what voltage does the OBC say you are getting when you first switch on and then when it is idling?

[Nrick]

Sounds a lot like low voltage rather than an issue with the trans or TCM. It would also account for the difficulty starting and the car stalling. A close inspection of the battery/charging system may be in order. Meanwhile, what voltage does the OBC say you are getting when you first switch on and then when it is idling?

Voltage reads 11.8-12 when off and key in position 2, voltage reads 14-14.4 when on and idling, voltage read down to 9.00 when cranking

[whiskychaser]

Yep. 11.8 is only about 30% charged. Probably enough to start the car but not enough to keep the TCM happy and working. Idle voltage looks good as that is when the alternator has kicked in. You have to ask, why is the battery voltage so low but the charging voltage looks good? I'd charge up the battery and see if you can spot the voltage dropping. Might be something as simple as a bad connection

[Nrick]

Yep. 11.8 is only about 30% charged. Probably enough to start the car but not enough to keep the TCM happy and working. Idle voltage looks good as that is when the alternator has kicked in. You have to ask, why is the battery voltage so low but the charging voltage looks good? I'd charge up the battery and see if you can spot the voltage dropping. Might be something as simple as a bad connection

The obc reads the voltage at 14-14.4, but also occasionally at 12-13. Had it checked out at Autozone and they said the battery was fine and the issue was the voltage regulator in the alternator.

[bd92]

Could be due to the lack of ASC? If I remember correctly, disconnecting my TPS on my e34 caused a trans prog to appear. It was after I changed the manifold gaskets and forgot to reconnect the TPS sensor. Again, it's been a few years so maybe I am remembering wrong.

[Nrick]

Could be due to the lack of ASC? If I remember correctly, disconnecting my TPS on my e34 caused a trans prog to appear. It was after I changed the manifold gaskets and forgot to reconnect the TPS sensor. Again, it's been a few years so maybe I am remembering wrong.

I'm not entirely sure. I have noted that the trans program error usually comes up the same time the dash reads S and P for mode and gear selected. I don't know if that helps anyone but that sounds like a sensor to me. Perhaps the gear selector switch needs a good cleaning/replace?