Allison Transmission Gen 4 / 5 Connector Pin-Outs
Allison Gen 4 / 5:
Allison Transmissions B400R / B500R that are Gen 4 / 5, use the same style connectors for the TCM and valve body. These pin-outs are beneficial for component and harness testing.
Allison High Side Drivers (HSD):
Allison transmissions use three High Side Drivers (HSD) to energize groups of PCS (Pressure Controlled Solenoid). This minimizes wiring.
⇒ Once the ignition is turned on, the TCM will send power through all three HSD’s, The TCM will energize the PCS’s by sending a ground PWM (Pulse Modulated Signal) through the solenoid ground wire to complete the circuit.
⇒ The power going through the PCS’s also serve as a feedback to check the wiring and the solenoids. Since the power will back feed through the ground circuit back to the TCM.
⇒ Another thing to note is that the TCM will not log a DTC (Diagnostic Trouble Code) with the ignition on and a component disconnected, open or shorted. It will only log once the vehicle engine is started.
⇒ Average operating voltage to PCS’s is approximately 6-7 volts.
⇒HSD 1 – Energizes PCS-4, Main Mod and PCS-6 (Seven Speed)
⇒HSD 2 – Energizes PCS-1, PCS-2, PCS-3 and SS1 (Shift Sol. 1)
⇒HSD 3 – Energizes TCC (Torque Converter Clutch), SS2 (Shift Sol. 2) and PCS-5
TCM 80 Pin:
TCM 80 Pin Connector:
20 Pin Connector to Valve Body:
20 Pin Valve Body Connector: