B1968

Code

Other B — Body

A/C Water Pump Detection Circuit Failure

Brand: Other

Type: B — Body

Views: UK: 24 EN: 29 RU: 25

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Page language: EN

Causes

Open or shorted wiring in pump power or detection circuit
Corroded, bent or disconnected pump connector
Blown fuse or faulty relay for pump supply
Failed A/C water pump motor
High-resistance connection (corrosion, damaged terminal)
Faulty body control module / HVAC control module or software fault

Symptoms

DTC stored and possible HVAC/A/C system warning lamp/message
A/C water/condensate pump does not run when A/C or heater is in modes that should operate it
Water accumulating or leaking in passenger footwell or under dash
Reduced or inconsistent A/C/defogging performance
Intermittent operation of pump or clicking relay noises

What to check

Read stored codes and freeze-frame/vehicle data with a scan tool; check for related HVAC or body module codes
Visual inspection of pump, harness, connectors, mounting and for signs of water intrusion or physical damage
Check relevant fuses and relays for the pump circuit
Backprobe pump connector while commanding pump ON; measure supply voltage and ground presence
Measure pump motor resistance and compare to specification (consult vehicle data)
Measure current draw while pump is running; compare to normal range

Signal parameters

Expected supply voltage: approximately battery voltage (~11–14.5 V) when commanded ON
Expected detection/feedback voltage: near 0 V (ground) or switched voltage depending on manufacturer design — consult service data
Motor resistance: typically low (single-digit ohms to tens of ohms) — check vehicle-specific spec
Running current: typically a few amps (commonly 0.5–10 A depending on pump) — consult spec
If PWM control used: frequency commonly in the 20–300 Hz range and duty cycle varies with demand

Diagnostic algorithm

Capture freeze-frame and live data. Note conditions when code set and any related codes.
Perform a visual inspection of the pump, connector and wiring for corrosion, damage or water ingress.
Check fuses and relays in the pump circuit; replace if faulty.
With ignition ON (engine off unless specified), backprobe the pump connector. Command pump ON via scan tool and verify supply voltage appears at the power terminal.
If supply voltage is present but pump does not run, measure motor resistance and current draw by supplying battery voltage through a fused jumper to the pump. If motor does not draw expected current or is open, replace pump.
If no supply voltage at connector when commanded, trace wiring back to relay/fuse and control module. Check continuity for open circuits and measure for shorts to ground or battery.
Wiggle harnesses and connectors while monitoring voltage and scan tool data to find intermittent faults.
If control module output is abnormal but wiring and pump test good, check for module software updates and consider module replacement only after verifying wiring and pump operation.
Repair or replace failed components (connector, wiring, fuse, relay, pump). Clear codes and re-test under the same conditions to confirm repair.

Likely causes

Pump connector corroded or pins pushed out causing intermittent contact
Wire chafe or pinched harness causing short to ground or battery
Pump seized or seized bearings causing no current flow or abnormal draw
Blown fuse or stuck relay preventing proper voltage to pump
Control module outputs not switching due to internal failure

Fault status

⚠️ Status

Control module reports failure in A/C water pump detection circuit — detection signal out of expected range (open/short/high resistance) preventing verification of pump operation.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.5 hours