I just replaced a 28100 PXO 832 M1 TCU with a 28100 PXO 731 TCU from a wrecked 91 Accord LX. What happens: In Park: No S Light; in R, no S light, N=no S light; D4= S LIGHT IS ON SOLID, but weak; D3 = No S light; D2=No S Light; D1 = No S light. While in Park, depressing the "S" Switch on the gear selector lever DOES NOT activate the S light for Speed Shift. Trans shifts normally and at expected rpm's.

Shorting the Service Port throws NO CODES. Opened the case. R41 & R42 are OK. No visible burns or shorts on inside of case or on the circuit board, front nor back.

Would this mean this TCU is incompatible with the system of an EX? Or is the Shift Position sensor be-fouled?

 

I would personally find a TCU I KNOW to be compatible. They are only 80 bucks on Ebay.

 

sadly, I haven't the time to wait for an auction to be over. The thing shifts as well as the 832 did before the partial burn-out. Any idea how one reads the codes to know if they're compatible from DX, LX, EX?