Allison 1000 & 2000 Gen 4 Fault Codes: P1891 Engine Throttle Position Sensor Pulse Width Modulation (PWM) Signal Low Input CIRCUIT DESCRIPTION:The Transmission Control Module (TCM) can be calibrated to receive throttle information from a Pulse Width Modulation (PWM) signal. CONDITIONS FOR RUNNING THE DTC:1. The components are powered and ignition voltage is greater than 9V and less than 18V (12V TCM) or greater than 18V and less than 32V (24V TCM).2. The components are powered and engine speed is within a 5 rpm range for 5 seconds. CONDITIONS FOR SETTING THE DTC:DTC P1891 sets if the TCM is calibrated...

Allison 1000 & 2000 Gen 4 Fault Codes: P1892 Throttle Position Sensor Pulse Width Modulation (PWM) Signal High Input CIRCUIT DESCRIPTION:The Transmission Control Module (TCM) can be calibrated to receive throttle information from a Pulse Width Modulation (PWM) signal. CONDITIONS FOR RUNNING THE DTC:1. The components are powered and ignition voltage is greater than 9V and less than 18V (12V TCM) or greater than 18V and less than 32V (24V TCM).2. Engine speed is greater than 200 rpm and less than 7500 rpm for 5 seconds. CONDITIONS FOR SETTING THE DTC:DTC P1892 sets if the TCM is calibrated to receive...

Allison 1000 & 2000 Gen 4 Fault Codes: P2771 Four-Wheel Drive Switch Circuit CIRCUIT DESCRIPTION:Detects abnormal conditions for the four-wheel drive indication switch input. Four wheel-drive statuses are detected using speed and ratios. CONDITIONS FOR RUNNING THE DTC:1. The components are powered and ignition voltage is greater than 9V and less than 18V (12V TCM) or greater than 18V and less than 32V (24V TCM).2. Engine speed is greater than 200 rpm and less than 7500 rpm for 5 seconds.3. DTCs P0721 and P0722 (output speed sensor circuits) are not active.4. Output speed is above 60 rpm.5. Transmission fluid temperature...

Allison 1000 & 2000 Gen 4 Fault Codes: P2773 Torque Control Request Ignored – ECM/TCM CIRCUIT DESCRIPTION:Shift Energy Management (SEM) allows the Transmission Control Module (TCM) to request torque reduction from the engine controller. By reducing torque during upshifts, shifts can be made quicker and at a more consistent output torque. This increases clutch life by reducing clutch engagement temperatures. CONDITIONS FOR RUNNING THE DTC:1. DTC U2105 CAN bus error is not active.2. The components are powered and ignition voltage is greater than 9V and less than 18V (12V TCM) or greater 18V and less than 32V (24V TCM).3. Engine...

Allison 1000 & 2000 Gen 4 Fault Codes: P2810 Solenoid G Electrical CIRCUIT DESCRIPTION:Solenoid G is a normally closed (N/C) solenoid used to modulate the transmission main pressure schedule. The TCM commands the G solenoid ON when specific transmission and engine conditions are met. When G solenoid is applied, pressure is routed to the main regulator valve. This in turn reduces the main pressure schedule and improves the volume of oil sent through the overage circuit. By modulating main pressure, cooler flow can be increased, allowing improved cooling and reduced pump noise. CONDITIONS FOR RUNNING THE DTC:1. The components are...