B0258 code meaning
HVAC Air Mix Door 1 Circuit
What B0258 means
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.
B0258 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor1 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of B0258
- Air from the vents stays hot or cold whatever temperature is set
- Clicking or knocking behind the dashboard when the temperature is changed
Common causes of B0258
- Most likelyBlend door actuator motor or its feedback potentiometer failed
- PossibleActuator plug or wires under the dashboard loose, chafed or shorted
- Less likelyDoor jammed by debris or a broken shaft, overloading the motor drive
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Hvac air mix actuatorHvac control module
What each part of B0258 means
| B | Body system: airbags, seat belts, power seats, lights and climate control. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 58 | The exact fault in that area. |
What to do next
- Note B0258 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about B0258
What does B0258 mean?
B0258 means "HVAC Air Mix Door 1 Circuit". The public J2012 sources do not list B0258, and no carmaker documents it publicly; it cannot be verified. It is a generic code, so it means the same on every make.
Is it safe to drive with B0258?
B0258 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will B0258 fail an emissions test?
B0258 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is B0258 to fix?
Difficulty: medium. A typical repair takes 1 to 4 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will B0258 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.