Body, generic

B0258 HVAC Air Mix Door 1 Circuit

Check engine lightUsually off

EmissionsNot relevant

Drive cycleNot required

Limp modeNo

The public J2012 sources do not list B0258, and no carmaker documents it publicly; it cannot be verified. GM's Global A system logs its left, or main, temperature actuator under B0408 instead, as the 2011 Saab 9-5 manual shows. Air mix door 1 is normally the main or driver-side blend door and divides the air between heater core and bypass. In dual-zone units each side has its own doors: Valeo's US6484755B1 places both zone actuators on one side of the case so that one access route serves both. Most actuators are reversible DC motors with a position potentiometer on the gear train, giving a signal between about 0 and 5 V according to MOTOR magazine. A circuit fault leaves the door where it stopped, so the outlet temperature no longer follows the setting.

Likely causes

Blend door actuator motor or its feedback potentiometer failed

Actuator plug or wires under the dashboard loose, chafed or shorted

Door jammed by debris or a broken shaft, overloading the motor drive

Symptoms

Air from the vents stays hot or cold whatever temperature is set
Clicking or knocking behind the dashboard when the temperature is changed

Repair estimate

DifficultyMediumDIY possible

Parts and labour€80–500

Time1–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

hvac air mix actuatorhvac control module

Related codes

B0263 B0168

References: saabwisonline.com, patents.google.com, motor.com.