Allison 1000 & 2000 Gen 4 Fault Codes: U1301 J1850 (Class 2) Serial Data Communication Link Low CIRCUIT DESCRIPTION:Applications that employ J1850 class 2 serial communication use wire 130 to send operational information and commands among the various control modules. Included modules would be Powertrain Control Module (PCM), Antilock Brake System (ABS) Controller, Truck Body Controller (TBC), and Instrument Panel Cluster (IPC). Each controller sends out a state of health (SOH) message approximately once every second. The TCM uses these SOH messages to monitor the condition of the devices on the class 2 serial link. CONDITIONS FOR RUNNING THE DTC:The...

Allison 1000 & 2000 Gen 4 Fault Codes: U2104 CAN Bus Reset Counter Overrun CIRCUIT DESCRIPTION:J1939 is the protocol currently used in medium duty applications to allow communication between an electronically-controlled engine and the OEM transmission. A signal is sent over a two-wire network harness that incorporates two 120 Ohm resistors in parallel. There are two versions of J1939 currently in use in the medium duty market. Version J1939-11, the most widely used, incorporates a third shield wire. There is also J1939-15, which uses a two-wire connection without shielding. CONDITIONS FOR RUNNING THE DTC:1. The components are powered and ignition...

Allison 1000 & 2000 Gen 4 Fault Codes: U2105 CAN Bus ECM Error CIRCUIT DESCRIPTION:J1939 is the protocol currently used in medium duty applications to allow communication between an electronically-controlled engine and the OEM transmission. A signal is sent over a two-wire network harness that incorporates two 120 Ohm resistors in parallel. There are two versions of J1939 currently in use in the medium duty market. Version J1939-11, the most widely used, incorporates a third shield wire. There is also J1939-15, which uses a two-wire connection without shielding. CONDITIONS FOR RUNNING THE DTC:1. The components are powered and ignition voltage...

Allison 1000 & 2000 Gen 4 P0719 Brake Switch ABS Input Low CIRCUIT DESCRIPTION: If the vehicle is equipped with anti-lock brake system (ABS), an interface between the ABS and TCM is required. This interface allows disengagement of the Torque Converter Clutch (TCC) when the ABS is activated. This ABS action is initiated with a discrete input from the ABS system, when the ABS is activated a ground signal is sent to TCM input wire 113. This may be a ground signal direct from the ABS controller or a positive signal from the ABS controller that powers a relay field coil to supply...