P0505 Code (Symptoms, Causes, and How to Fix)

A check engine light and poor performance are worrisome signs. But code P0505 points to a straightforward issue – an idle control system malfunction. This impacts engine RPMs at idle, causing a rough run.

While frustrating, P0505 is an accessible DIY fix for many vehicles including many Honda, Nissan, and Dodge models. Here’s what causes DTC P0505, how serious it is, and how to fix the problem whether you drive a Honda, Nissan, Dodge, or most any other vehicle brand.

P0505 code

What Does Code P0505 Mean?

OBD-II Trouble Code P0505 Description
Idle Air Control System Malfunction

The description “Idle Air Control System” really doesn’t tell you much about what’s going on – it only lists a component. But the problem is somewhere within that component, so it’s a good idea to know how it works.

The idle air control system controls the current idle speed of your vehicle to match conditions and it does this by controlling how much air gets through the throttle body.

The correct amount of air needed to keep steady idle changes depending on a variety of conditions, including the ambient air temperature, altitude, and internal loads like the air conditioning.

With a code P0505, it means that the system isn’t working properly, which has several significant implications.

Related: P0506 Code, P0507 Code

Symptoms of Code P0505

rough idling

While you’ll obviously have a check engine light if you have a code P0505, that’s likely not the only symptom you’ll notice. More often than not, you’ll have a low engine idle under specific conditions – especially when the engine is under a higher load.

In fact, the engine might even die when you have the vehicle stopped. You’ll also likely have a rough idle since the vehicle can no longer adjust to the different conditions your vehicle goes through.

The sound of a vacuum leak coming from your engine is also a possibility. Finally, while a low idle is the most likely result of a code P0505, it is possible to have a high idle with this code as well.

Really any idle condition that isn’t normal is a telltale sign of a code P0505 since it has everything to do with keeping your vehicles idle in check.

  • Check engine light
  • Low engine idle
  • Rough idle
  • High idle
  • Stalling

Causes of Code P0505

idle air control motor

There are several potential causes of a code P0505, but the two most likely are a defective idle control motor or an intake manifold vacuum leak. That’s because the idle air control motor typically runs on vacuum, so if there’s a leak it won’t work the way it’s supposed to!

It also means that if you replace the motor, it won’t do a thing. While those are the two most likely causes, the problem could also be a carbon buildup in the throttle body keeping it from working the way it should, or an electrical problem between the idle air control motor and the PCM.

  • Defective idle air control motor
  • Intake manifold vacuum leak
  • Carbon buildup in IAC valve
  • Carbon buildup in the throttle body
  • Electrical wiring problem

Is Code P0505 Serious?

A code P0505 might feel like one that you can drive around for a bit on, but that’s far from the truth. That’s because a code P0505 creates a multitude of rough conditions for the rest of your engine, and if you drive around for too long on it, you’re going to cause further engine damage.

Not only that, but there’s a good chance that your engine will randomly stall at stoplights, stop signs, or if you’re stuck in traffic. Not only is that annoying, but it can create unsafe driving conditions. So, if you have a code P0505 it’s crucial you address it as soon as possible.

How to Fix

loose vacuum hoses

While a code P0505 doesn’t necessarily indicate the most expensive repairs, it’s not exactly the easiest to troubleshoot. That’s because while most engine codes point you towards a sensor of some sort, a code P0505 doesn’t.

When troubleshooting a code P0505 it’s typically easiest to figure out what’s going on by ruling things out. Start by hooking up a smoke machine to the vacuum system to test for leaks. If there’s no leak in the vacuum system, the problem is likely with the idle air control motor.

To check, start by unplugging the motor and seeing if it changes the idle of the vehicle. If it doesn’t, there’s a good chance the problem is the motor itself. But before jumping to replace the motor, check for power. The last thing you want to do is replace the motor only to realize the problem was with a connector!

If the idle does change when you unplug the motor, chances are that’s not the problem. Try cleaning the throttle body, as sometimes carbon buildup can lead to a code P0505, which mirrors a faulty idle air control motor.

If you still can’t figure out what’s going on at this point, consider taking your vehicle to a qualified mechanic to help you troubleshoot the problem.

Adam Mann

Leave a Reply

Your email address will not be published. Required fields are marked *