P0505 on a Honda Civic
P0505 means idle Air Control System Malfunction. On the Civic, a few causes come up far more than others.
What P0505 usually means on a Civic
P0505 points to the Civic's idle control system not maintaining the commanded idle. On the older Civics that use an idle air control valve, a carbon-clogged IACV is the classic cause and produces a hunting or stalling idle. The valve sits on the throttle body and gums up over the years. Cleaning it resolves a large share of these.
Most common causes on the Civic
- Carbon-clogged IACV
The idle air control valve cokes up on high-mileage Civics, causing surging or stalling and setting P0505.
- Dirty throttle body
Deposits around the throttle plate disturb idle airflow the ECU cannot correct.
- Vacuum leak affecting idle
An unmetered air leak makes the idle system run out of authority.
What P0505 costs to fix on a Civic
Cleaning the IACV and throttle body is nearly free if you do it yourself and inexpensive at a shop, and it fixes many P0505 Civics. A replacement IACV is a moderate part if cleaning does not hold. This is one of the cheaper idle-related repairs on the platform.
Year, engine and mileage change the answer. Start a case and Redline weighs these causes against what your car shows, then names the check that would settle it.
Other codes on the Honda Civic
Related symptoms
Honda Civic problems & recalls by year
Based on widely reported patterns for this model; individual causes vary by year, engine and history. Generic P0505 behavior is covered on the main P0505 page. Confirm with a scan tool before buying parts.
P0505 on your Civic?
Every problem becomes a Case. Tell Redline what your Civic is doing: it shows what the evidence supports, what’s still missing, and what to check next, before you approve a repair.
“Inner pad ~1 mm. Outer pad 3 mm.”
Next: check the slide pins move freely before buying parts.