B12444B - B12444B Passenger Side PTC Core Overheat

Fault Depth Definition

This fault code (DTC: B12444B) is identified as Passenger side PTC core overheating, playing a key monitoring and diagnostic role in the whole vehicle thermal management system. This code indicates that the Vehicle Control Unit (ECU) or Air Conditioning Controller has detected that the heating element core temperature in the passenger area exceeds normal operating thresholds. As part of the passive safety and comfort adjustment system, this fault code defines state feedback when abnormal heat accumulation occurs inside the resistive heater and it fails to maintain the established thermal balance. In the electrical architecture, it marks a deviation in communication or physical status between the high voltage or pre-pressure PTC air heater module and the master control unit, requiring the system to enter specific protection logic to ensure whole vehicle electrical safety.

Common Fault Symptoms

When this fault is recorded, the experience of drivers and occupants inside the cabin will change as follows, which are perceivable instrument feedback or driving phenomena:

• Front-pressure PTC air heater function fails, outlet cannot provide expected heat output according to set temperature.
• Instrument panel HVAC indicator light may turn on, or display relevant fault prompt messages on the central control screen.
• Cabin heating efficiency significantly decreases, especially in low-temperature environments or high-load demand conditions, with delayed or unstable heating response.
• System may be accompanied by intermittent control signal interruptions, causing the heater to switch unexpectedly between heating and stopping.

Core Fault Cause Analysis

Based on diagnostic logic, fault roots can be systematically classified and analyzed from three dimensions of hardware, connection, and control:

• Hardware Component Abnormality: High voltage PTC air heater body has internal physical damage, such as resistor element breakage, insulation layer aging or control module (PCBA) overheat protection trigger, leading to inability to work normally.
• Wiring and Connector Faults: High voltage wiring harness connecting passenger side heating module has insulation layer damage, poor grounding, or relevant connectors cause excessive contact resistance due to thermal expansion and contraction, triggering signal transmission errors.
• Controller Logic Operation: Thermal management system software inside Air Conditioning Control Unit appears logical deviation, or sensor feedback data abnormal (such as temperature sensor drift), causing system to misjudge heating status as overheating and record fault.

Technical Monitoring and Trigger Logic

Fault judgment technical logic follows strict timing and condition control flow process, ensuring diagnosis only occurs in specific states:

• Monitoring Targets: System collects PTC core surface temperature signals, high voltage circuit current values and voltage stability in real-time, ensuring operation within safe working range.
• Trigger Conditions: Fault judgment takes effect only when start switch is in ON position. In this state, control unit activates heating relay or power drive module, beginning dynamic detection on thermal management loop.
• Judgment Threshold Logic: When monitored core temperature exceeds preset safety upper limit $T_{max}$, and duration satisfies diagnostic algorithm required window period, system records fault code and terminates related function output to prevent hardware from damage due to continuous overheating.