11-06-2017, 03:51 PM
I'm posting this for future reference.
The HT-741 needs to know the throttle position in order to decide how hard to slam together the clutches for the various gears. Below 60% throttle is soft shifts, above that is hard shifts. The engine computer has an output signal that shows the throttle position. That signal has to go through a conversion circuit in order to be used by the transmission ECU. That conversion takes place inside a 2" square black plastic box mounted on the right firewall of the engine compartment. Mine says "KDS Controls" on it. One wire into it is crimp spliced to the wire from the engine DDEC and the three wire black plastic detachable connector goes to the transmission ECU.
The "Check Trans" light will be on whenever the ignition key is on and the engine is off. Once the engine starts, the oil pressure switch mounted on the right rear of the 8V92TA engine allows the ECU to enter its startup test flash of the light. If there are trouble codes detected by the engine, with the engine running you can flip the "Check Trans" switch up and read the trouble codes as flashes of the light. The codes will remain stored in the ECU as long as there is battery power to the ECU (separate source from either the ignition switch or from the oil pressure switch). I'm not sure whether turning off the battery shutoff switch will delete the codes. Unless you have a Allison code reader instrument the standard way of resetting codes is to disconnect battery power.
The HT-741 needs to know the throttle position in order to decide how hard to slam together the clutches for the various gears. Below 60% throttle is soft shifts, above that is hard shifts. The engine computer has an output signal that shows the throttle position. That signal has to go through a conversion circuit in order to be used by the transmission ECU. That conversion takes place inside a 2" square black plastic box mounted on the right firewall of the engine compartment. Mine says "KDS Controls" on it. One wire into it is crimp spliced to the wire from the engine DDEC and the three wire black plastic detachable connector goes to the transmission ECU.
The "Check Trans" light will be on whenever the ignition key is on and the engine is off. Once the engine starts, the oil pressure switch mounted on the right rear of the 8V92TA engine allows the ECU to enter its startup test flash of the light. If there are trouble codes detected by the engine, with the engine running you can flip the "Check Trans" switch up and read the trouble codes as flashes of the light. The codes will remain stored in the ECU as long as there is battery power to the ECU (separate source from either the ignition switch or from the oil pressure switch). I'm not sure whether turning off the battery shutoff switch will delete the codes. Unless you have a Allison code reader instrument the standard way of resetting codes is to disconnect battery power.
Jon Kabbe
1993 coach 337 with Civic towed