Turbocharger System: Operation

When the key is cycled to the ON position, the Powertrain Control Module (PCM) wakes the Low Temperature Radiator (LTR) pump. A signal carried over the Local Interface Network (LIN) is based on an ignition signal from the Auto Shut Down (ASD) relay. At key ON the PCM determines the pump speed by using a calibrated lookup table. The lookup table defines the relation between pressure ratio and Temperature/Manifold Absolute Pressure (TMAP) temperature input. If the PCM detects an increase in the pressure ratio/average temperature the PCM will then increase pump speed. If PCM detects cold start, PCM shall control the pump at lower speeds (than the lookup table speed) to help the engine warm up quickly. This feature is enabled or disabled by calibration only. A calibrated minimum speed is always required from PCM to LTR coolant pump in order to maintain a minimum flow rate during normal operation.

The LTR pump has a pre-run (key ON engine OFF) and a post-run (key OFF engine OFF) operation. At key ON engine OFF, the PCM controls the LTR pump speed by a calibrated lookup table. This lookup table defines the pump speed in relation to LTR coolant temperature value and ambient temperature. If dry run is detected, the PCM stops commanding the pump immediately to prevent any component damage. The PCM is able to detect pump faults during the Pre-run cycle to protect any component damage. Pre Run time is a calibrated amount of time determined by engine thermal characteristics and vehicle charging system limits (state of charge).

LTR pump post-run cycle will continue to operate even if the PCM is powered off as long as it gets the after run command from PCM before it has been powered down. Immediately after key OFF, the PCM will send the pump post-run command using LIN bus before sending LIN sleep command. After the PCM sends the pump post-run command, the PCM receive signals back from the pump and then powers down the ASD relay. The LTR pump will turn off the post-run cycle immediately at key ON. Post-run time shall is a calibrated time and determined by engine thermal characteristics and vehicle charging system limits.