Circuit Description

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The powertrain control module (PCM) uses the rationality diagnostic to determine if the sensor is skewed to a higher temperature range that would reduce the amount of time that would otherwise be spent with the engine off at idle. The PCM uses the intake air temperature (IAT) sensor input and the ambient air temperature sensor input from the HVAC control module to calculate the approximate ambient air temperature.

The HVAC control also monitors the ambient air temperature sensor and sends the data to the hybrid control module (HCM). The PCM monitors the intake air temperature sensor and sends the data to the HCM. The HCM uses these two data parameters to determine if the ambient air temperature sensor may not be with in range. If the HCM determines that the IAT sensor is 10° C (18° F) greater than the ambient air temperature sensor input, then DTC B0159 will set.