Engine

P1507 — Idle Speed Too Low: Idle Control Cannot Raise RPM

Severity: medium Drive with care, to a shop

What P1507 means

The engine control unit compares actual idle speed with a target and adds air through the idle air control (IAC) valve or the electronic throttle. P1507 is set when RPM stays below target even though the system is adding as much air as it can. That points to too little air reaching the engine or an actuator that cannot deliver it.

Symptoms

  • Rough, hunting or very low idle
  • Stalling at stops or when slowing down
  • Stalling when a load is added (A/C, steering, lights)
  • Hard starting or RPM dropping right after startup
  • Check Engine light on

Possible causes

  1. Vacuum or intake air leak (hoses, gaskets, boots)
  2. Dirty throttle body
  3. Failed or sticking idle air control valve
  4. Carbon buildup in idle air passages or bypass
  5. Open, corroded or shorted wiring or connector at the IAC
  6. Faulty throttle position or mass airflow sensor

How to diagnose

  1. Scan for codes and freeze frame data and note any fuel trim or sensor codes
  2. Inspect intake ducts, vacuum hoses and the air intake boot for cracks and loose joints
  3. Smoke test the intake or carefully spray cleaner around joints to find air leaks
  4. Remove the throttle body and check the plate and idle passages for carbon
  5. Check the IAC connector, wiring, power and ground, and measure coil resistance against specs
  6. Command the IAC with a scan tool and confirm RPM responds
  7. Check mass airflow and throttle position readings for plausibility
  8. After repair, clear the code and run the idle relearn procedure

Common fixes

  • Repair intake leaks: replace hoses, gaskets or seals
  • Clean the throttle body and idle air passages
  • Replace the idle air control valve
  • Repair damaged IAC wiring or connector
  • Perform throttle and idle relearn after cleaning or replacement

P1507 on different brands

Ford · manuals
Idle Air Control Under Speed Error: the module could not raise idle RPM to the target.
Hyundai · manuals
Idle speed control actuator signal low on coil #2.
Jaguar
The manufacturer lists the IAC RPM as higher than expected, so check freeze frame data carefully.
Kia · manuals
Idle air control valve closing coil signal low.
Land Rover
Idle air control value low; the code points to the circuit or function rather than one specific failure.
Lexus · manuals
The manufacturer description refers to a disabled PTC auxiliary heater, so confirm against model-specific documentation.
Mazda · manuals
Idle air control system underspeed error: idle RPM stayed below target.
MINI
Idle speed control valve open solenoid control circuit signal low.

Questions and answers

What does P1507 mean?

The engine control unit sees idle speed below target and the idle air control cannot bring it up. Common causes are a vacuum leak, a dirty throttle body or a bad IAC valve.

Can I drive with P1507?

Briefly, yes, but the engine may stall at stops or while maneuvering. Do not put off diagnosis.

Will cleaning the throttle body fix it?

Often, especially if the idle passages are clogged with carbon. Run an idle relearn afterward or idle may stay unstable.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.