AutoCodes – Generic – P1504

P1504 Code - Intake Air Control Circuit Malfunction

Quick Answer

The Idle Air Control Valve (IACV) valve assembly controls the engine idle speed and provides a dashpot function. Common causes include Faulty Idle Air Control Valve, Idle Air Control Valve harness is open or shorted, Idle Air Control Valve circuit poor electrical connection. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: P1504 indicates Intake Air Control Circuit Malfunction.
Common causes: Common causes include Faulty Idle Air Control Valve, Idle Air Control Valve harness is open or shorted, Idle Air Control Valve circuit poor electrical connection.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 53,016

How popular is this code, among other codes? Medium

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Aug 25, 2019

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P1504 Description

The Idle Air Control Valve (IACV) valve assembly controls the engine idle speed and provides a dashpot function. The IAC valve assembly meters intake air around the throttle plate through a bypass within the IAC valve assembly and throttle body. The Powertrain Control Module (PCM) determines the desired idle speed or bypass air and signals the IAC valve assembly through a specified duty cycle. The IAC valve responds by positioning the IAC valve to control the amount of bypassed air. The PCM monitors engine RPM and increases or decreases the IAC duty cycle in order to achieve the desired RPM.

OBDII Code P1504 - Intake Air Control Circuit Malfunction - AutoCodes.com — P1504 Code - Intake Air Control Circuit Malfunction

What does this mean?

What are the Possible Causes of the DTC P1504?

Faulty Idle Air Control Valve
Idle Air Control Valve harness is open or shorted
Idle Air Control Valve circuit poor electrical connection
Faulty Powertrain Control Module (PCM)

How to Fix the DTC P1504?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P1504 code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the P1504 code?

Need more information on how to fix the P1504 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P1504 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

P1504 Audi — Intake Air System Bypass Leak Detected
P1504 BMW — Idle Speed Control Valve Closing Solenoid Control Open Circuit
P1504 Buick — Vehicle Speed Output Circuit
P1504 Cadillac — Vehicle Speed Output Circuit
P1504 Chevrolet — Vehicle Speed Output Circuit
P1504 Ford — Intake Air Control Circuit Malfunction
P1504 GMC — Vehicle Speed Output Circuit
P1504 Hyundai — Cruise Control Cancel Switch Fault
P1504 KIA — Cruise Control Cancel Switch Fault
P1504 Lincoln — Intake Air Control Circuit Malfunction
P1504 Mazda — IAC Electrical Load Failure
P1504 Mercury — Intake Air Control Circuit Malfunction
P1504 MINI — Idle Speed Control Valve Closing Solenoid Control Open Circuit
P1504 Subaru — Vehicle Speed Sensor CAN Malfunction
P1504 Volkswagen — Intake Air System Bypass Leak Detected

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P1504 Code

1. What are some common symptoms of OBDII code P1504 (Intake Air Control Circuit Malfunction)?

- Common symptoms include rough idling, stalling, poor engine performance, and illuminated Check Engine Light.

2. What can cause OBDII code P1504 to trigger?

- The code may be triggered by a faulty intake air control valve, wiring issues, vacuum leaks, or a malfunctioning PCM.

3. How can I diagnose the cause of OBDII code P1504?

- Diagnose by checking the intake air control valve for proper operation, inspecting the wiring for damage, testing for vacuum leaks, and scanning the PCM for fault codes.

4. What are some repair tips for fixing OBDII code P1504?

- Repair tips include cleaning or replacing the intake air control valve, repairing damaged wiring, fixing vacuum leaks, and resetting the PCM after repairs.

5. Can I drive with OBDII code P1504 active?

- It is generally not recommended to drive with this code active, as it can lead to further engine damage and poor performance.

6. Will resetting the PCM clear OBDII code P1504 permanently?

- Resetting the PCM may temporarily clear the code, but if the underlying issue is not fixed, the code is likely to return.

7. How much does it typically cost to repair OBDII code P1504?

- The cost of repair can vary depending on the specific cause, but it may range from $100 to $300 for parts and labor.

8. Can I prevent OBDII code P1504 from occurring?

- Regular maintenance, such as cleaning or replacing air filters, inspecting vacuum lines, and checking wiring connections, can help prevent this code.

9. Is OBDII code P1504 a serious issue?

- While the code itself may not cause immediate harm, ignoring it can lead to engine performance issues and potential damage over time.

10. Can a DIY enthusiast fix OBDII code P1504 at home?

- Depending on the cause, some DIY enthusiasts with automotive repair experience may be able to fix this issue at home by following repair guides and using appropriate tools.