Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Circuit Description
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.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.