B1268

Code

Other B — Body

Servo Motor Potentiometer Defrost Circuit Failure

Brand: Other

Type: B — Body

Views: UK: 23 EN: 31 RU: 74

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Page language: EN

Causes

Failed/dirty/contaminated potentiometer inside the HVAC servo (actuator)
Open, shorted or pinched wiring in the potentiometer signal, reference, or ground circuits
Corroded or loose connector(s) at the actuator or control module
Poor or missing ground at the actuator or control module
Water intrusion or physical damage to the actuator harness or connector
Faulty climate control / body control module (rare)

Symptoms

Defrost or vent doors not moving to commanded positions
Intermittent or incorrect airflow distribution (wrong vents selecting)
HVAC may stay in one mode or fail to auto-select defrost
Blower may run but vents don’t respond to mode changes
Possible diagnostic trouble light or HVAC warning message on dash (vehicle-dependent)

What to check

Retrieve full DTC record and any related HVAC/body codes with a scan tool
Visually inspect actuator, wiring harness and connectors for corrosion, damage, water ingress, or rodent chew
Operate HVAC modes with a scan tool while observing actuator position/feedback values
Backprobe actuator connector and check reference voltage (usually ~5V) and ground presence
Measure potentiometer output signal voltage while moving actuator (should vary smoothly)
Check continuity and resistance of signal, reference and ground wires between actuator and control module

Signal parameters

Typical reference voltage: ~5.0 V (depends on manufacturer — verify spec)
Potentiometer signal: variable 0.0–5.0 V as door/shaft moves (should change smoothly without drops/spikes)
Typical potentiometer resistance: commonly 1 kΩ–20 kΩ range (manufacturer-specific)
No open circuit between ground pin and chassis ground; continuity should be near 0 Ω

Diagnostic algorithm

Use a scan tool: read and record B1268 and any related codes; capture live data for the actuator position/potentiometer signal. 2) Confirm symptom: verify defrost/vent operation and reproduce fault. 3) Visual inspection: check actuator, connector, and harness for damage, corrosion, or water. 4) Backprobe connector with ignition ON: verify reference voltage present (≈5V), continuity to module, and solid ground. 5) Command actuator via scan tool while watching live potentiometer voltage; observe for smooth variable voltage. 6) If signal is stuck, open, or intermittent, perform continuity/resistance checks from actuator pins to control module pins. 7) Wiggle harness and connector while monitoring for changes; if intermittent, repair or replace wiring/connector. 8) If wiring and connector are good but potentiometer signal is faulty, replace the servo/actuator assembly. 9) After repairs, clear codes and perform full system function test and calibration (if required). 10) If problem persists with correct wiring and new actuator, suspect control module fault and verify module inputs/outputs per manufacturer procedures.

Likely causes

Failed potentiometer inside the defrost/vent servo (most common)
Connector corrosion or damaged wiring between the servo and control module
Poor ground at the actuator harness or control module

Fault status

⚠️ Status

Stored when the HVAC control detects an open/short/invalid feedback signal from the defrost/vent servo potentiometer. May disable or impair automatic defrost/vent door control until repaired.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5–2 hours