OBD Guide
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P158C

Idle Air Control Actuator 1 Self-Test Fault

P158C is an OBD-II diagnostic trouble code meaning: Idle Air Control Actuator 1 Self-Test Fault. Common causes: malfunction of the idle speed actuator, contamination or blockage of the idle air passage. Estimated repair cost: $17–56.

Severity
⚠️ Medium
Can you drive?
Limited driving only, diagnose soon
Approx. repair cost
$17–56 (est.)

Symptoms

  • Unstable idle speed
  • Floating engine speed
  • High or low idle speed
  • Difficulty starting the engine
  • Stalls at idle

Causes

  • Malfunction of the idle speed actuator
  • Contamination or blockage of the idle air passage
  • Open or short circuit in control circuit
  • Poor contact in actuator connector
  • Software error in the engine control unit

How to Fix

  1. Check the condition of the idle channel for contamination
  2. Test the idle speed actuator
  3. Check the integrity of the control circuit and connectors
  4. Clean or replace the actuator if necessary
  5. Update ECU firmware (if required)

Related codes

P0505P0506P0507

FAQ

What does the P158C code mean?

P158C is an OBD-II diagnostic trouble code that indicates: Idle Air Control Actuator 1 Self-Test Fault

What causes a P158C error code?

The most common causes of P158C include: Malfunction of the idle speed actuator; Contamination or blockage of the idle air passage; Open or short circuit in control circuit; Poor contact in actuator connector.

How do I fix a P158C diagnostic trouble code?

To fix P158C: Check the condition of the idle channel for contamination. Test the idle speed actuator. Check the integrity of the control circuit and connectors. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with P158C?

Limited driving only, diagnose soon

How much does it cost to fix P158C?

The estimated repair cost for P158C is $17–56. Actual cost depends on your vehicle, location, and labor rates.

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