Code
P1110
PEUGEOT
P — Powertrain
A/C control malfunction
AI status
Completed
Completed
100%
Causes
- Faulty HVAC/A‑C control module (climate control unit)
- Loss of communication on CAN/BUS or wiring fault between modules
- Blown fuse or faulty relay for HVAC/AC system
- Damaged connectors or corroded terminals at control unit
- Faulty temperature/evaporator/ambient sensors providing invalid signals
- Faulty blower motor or blower motor resistor/module
Symptoms
- A/C or climate control panel unresponsive or partially responsive
- Loss of automatic climate control functions (auto mode not working)
- Compressor does not engage or engages intermittently
- Blower speed stuck at one setting or not working
- Incorrect cabin temperature or persistent fogging
- Warning lamp or message related to HVAC or A/C system on dash
What to check
- Read and record all stored and pending DTCs (scan tool) including U‑codes
- Check freeze frame/live data when fault set to reproduce behavior
- Visual inspection of HVAC control module connectors for corrosion, damage, or water ingress
- Check relevant fuses and relays for HVAC/A‑C circuits
- Check for proper supply voltage and ground at the HVAC control module
- Verify CAN/LIN communication with a scan tool: module present/responding
Signal parameters
- HVAC control supply voltage (nominal battery voltage, ~12V)
- HVAC control ground integrity (ohms to chassis)
- Presence of HVAC module on CAN bus (node responds to diagnostic tool)
- Blower motor command signal (PWM frequency/duty) and blower current draw
- Compressor request signal from control module to clutch (ON/OFF or PWM)
- Evaporator temperature sensor resistance/voltage
Diagnostic algorithm
- Connect a full‑function scan tool. Read and note all stored, pending and history DTCs and freeze frame data.
- Verify whether P1110 is current, pending or history. Clear codes and attempt to reproduce the fault while monitoring live data.
- Perform visual inspection: HVAC control unit connectors, wiring harness for chafing or water, and fuse/relay condition.
- With ignition on, check for correct supply voltage and a good ground at the HVAC control module connectors. Repair any open circuits or high resistance grounds.
- Confirm module presence on vehicle network: use scan tool to communicate with HVAC module and check for other modules reporting loss of communication (U‑codes).
- Verify sensor inputs (evaporator, cabin/ambient temp, pressure switch) are within expected ranges; test sensor resistances where applicable and compare to spec/known good values.
- Check compressor clutch operation: request compressor ON with scan tool and verify clutch energizes and compressor spins; check clutch coil resistance and supply when commanded.
- Verify blower motor and resistor/module operation by commanding fan speeds and measuring blower current; replace motor or resistor if faulty.
- If wiring, power and grounds are good and module still inoperative, consider software update/reflash of HVAC control unit per manufacturer procedure.
- Replace HVAC/AC control module only after confirming all inputs, power, ground and communications are correct. Reprogram/configure new module as required and verify repair by road/test and rescanning.
Likely causes
- Intermittent or poor electrical connection at HVAC control unit
- Blown fuse or failed relay supplying the control unit
- CAN/bus communication error between HVAC control and PCM/IPCU
- Failed HVAC control unit (most likely if wiring and power/ground check OK)
Fault status
Status
P1110 — A/C control malfunction. Stored when the HVAC/air‑conditioning control module detects an internal fault, invalid sensor inputs, loss of communication, or improper supply/ground conditions affecting A/C operation.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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