Changan CS15EV A/C System DTCs and Diagnostic Test Guide

Fault Background

The Changan CS15EV (775 manual) A/C system is jointly controlled by the thermal management system controller assembly (green/blue wiring harness connectors) and the electric A/C controller. DTCs B1400~B1411 cover sensors, actuators, water pumps, and CAN bus. Compared to the BenBen EV, this manual provides two additional layers of information: DTC setting conditions (e.g., evaporator temperature sensor resistance <25Ω for short, >900kΩ for 5 consecutive seconds for open, with 0.024V/4.97V feedback at 5V reference; DTC confirmed only if fault occurs in 200 test cycles) and fault symptom diagnostic procedures (three standard paths for insufficient cooling / blower not working / compressor not working, including manifold gauge set standard values high side 1.4~1.75MPa, low side 0.25~0.35MPa). This article organizes the DTC table and three major diagnostic procedures into a quick reference guide.

DTC Table (with Setting Conditions)

General rule: For sensor types, "test failure bit set in this detection cycle → fault occurs in all 200 test cycles → DTC confirmed"; for actuator types, thresholds based on position percentage (2%/98%) and stall (2s).

General Diagnostic Procedure (Five Steps)

① Visual inspection of related wiring harness connectors (damage/poor contact/aging/loose) → ② Clear DTCs with diagnostic scan tool, re-read after ignition operation; if no DTC, it's an intermittent fault → ③ Open circuit check (resistance between controller and component terminals standard <1Ω) → ④ Short circuit check (resistance between terminals standard ≥10MΩ) → ⑤ Power short check (signal terminal to reliable ground voltage standard 0V; water pump power terminal to ground 12V). If wiring is abnormal, replace the corresponding harness; if wiring is normal, replace the sensor/actuator/water pump; if still abnormal, finally replace the thermal management system controller assembly.

Symptom 1: Insufficient A/C Cooling

1. Start compressor and measure vent outlet temperature at instrument panel: too high → switch to recirculation, move to shade, adjust recirculation/fresh air damper mechanism (replace motor if necessary), inspect/replace air mix (blend) door control motor, replace refrigerant meeting manufacturer specifications;
2. Measure air volume: too low → clean/inspect air outlets, inspect wiring, inspect airflow direction control mechanism, inspect blower motor and speed control module;
3. Connect manifold gauge set to measure high/low side pressures: standard high side 1.4~1.75MPa, low side 0.25~0.35MPa. Deviations handled by five branches: both high→inspect line sealing, recharge, discharge excess refrigerant and compressor oil, replace expansion valve; high side high + low side low→clean/replace clogged high-pressure line, replace expansion valve; high side low + low side high→add compressor oil, inspect/replace compressor; both low→inspect/replace leaking components, recharge per standard; high side low + low side vacuum→replace receiver-drier and expansion valve, clean/replace low-pressure line, extend vacuum pump time, recharge per standard, replace evaporator temperature sensor;
4. Check compressor operating status (read feedback via CAN bus): plug/unplug high/low pressure connectors, add refrigerant/compressor oil, inspect suction/discharge lines, inspect A/C pressure switch, inspect evaporator temperature sensor, inspect compressor assembly, inspect A/C control panel, inspect thermal management control module;
5. Check condenser heat dissipation: inspect/clean condenser; cooling fan (fuse 30A): after A/C on, fan runs at low speed, high side ≥1.7MPa switches to high speed, <1.2MPa returns to low speed; thermal management system controller fuse 10A.

Symptom 2: Blower Not Working

Fuse (30A) → blower relay (try new relay) → relay power circuit (11~14V) → relay ground circuit (<5Ω) → blower voltage input (11~14V) → blower ground circuit (<5Ω) → blower to electric A/C controller circuit (<5Ω) → replace blower speed control module → replace electric A/C controller.

Symptom 3: A/C Compressor Not Working

Visual inspection (dents/damage/deformation → replace compressor assembly) → high/low pressure connectors and condenser fan, pressure switch connectors → refrigerant pressure (normal at ambient temperature 0.7MPa, if low check for leaks and recharge) → center console panel power (11~14V) and ground (<5Ω) → read DTCs: B1440 phase current overcurrent protection / B1441 internal module temperature too high / B1444 controller internal voltage → replace compressor; B1442 bus under/over voltage → high-voltage harness after-sales repair; B1443 controller and CAN bus bus off → CAN bus after-sales repair; B1400 evaporator temperature sensor / B1404 pressure sensor → corresponding after-sales repair → compressor low-voltage power supply (harness connector E33 pin 1 11~14V, measure in A/C cooling state) → refrigerant pressure switch (terminals 1-2 <1Ω, 0.7MPa at ambient temperature) → high-voltage harness power supply → replace center console panel to test → pressure switch and thermal management system controller harness (<5Ω) → replace thermal management system controller assembly.

Safety Warnings

• This article is for technical reference. A/C system involves high-voltage compressor and refrigerant operations; must be performed by qualified technicians (electrician certificate + company training authorization) per OEM specifications; refrigerant recovery and charging must use dedicated equipment.
• Before measuring wiring, power down (LOCK position + disconnect battery negative cable); when measuring power in ON position, prevent short circuits to ground.
• Compressor bus under/over voltage (B1442) and CAN bus off (B1443) involve high voltage and vehicle communication; refer to corresponding specialized repairs, do not forcibly replace parts within the A/C subsystem.

Repair Insights

The most practical upgrade in the CS15EV A/C DTC table is providing quantitative thresholds: sensor short/open is no longer "feels abnormal" but 25Ω/900kΩ, 10Ω/400kΩ two sets of hard thresholds, with 0.024V/4.97V feedback voltage at 5V reference—multimeter readings directly match the table, no need to disassemble and trial-replace. For actuators, remember 2%/98% position percentage + 2-second stall three rulers. For pressure diagnosis, remember the standard window 1.4~1.75 / 0.25~0.35MPa, five-branch handling logic (both high/high-low/low-high/both low/low-vacuum) covers all typical failure modes of the refrigeration system. Among them, the "high side low + low side vacuum" branch has the most actions: receiver-drier, expansion valve, low-pressure line, vacuum pump time, evaporator temperature sensor—handle all five together, don't just replace one. Finally, note the fan dual thresholds 1.7MPa speed up / 1.2MPa speed down—this is the fastest way to judge whether cooling fan control is normal.

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【This article is for reference only】