Vacuum Pump Control Circuit Low
The P258C code indicates that the powertrain control module (PCM) has detected a low voltage condition in the vacuum pump control circuit. This circuit controls the operation of the vacuum pump, which is essential for brake booster vacuum and other vacuum-operated systems. A low voltage reading suggests a short to ground, open circuit, or faulty component, potentially leading to reduced vacuum assist and increased braking effort.
1. Most Common Causes
- Faulty vacuum pump relay
- Open or shorted vacuum pump control circuit wiring
- Failed vacuum pump motor
- Corroded or loose electrical connector at vacuum pump
2. Symptoms You Will Notice
- Hard brake pedal (increased braking effort)
- Illuminated Check Engine Light
- Possible vacuum leak hissing sound
- Reduced engine performance or rough idle
3. Step-by-Step Diagnosis
Step 1: Use a scan tool to confirm P258C and check for other related codes.
Step 2: Visually inspect the vacuum pump and its electrical connector for damage, corrosion, or loose connections.
Step 3: Test the vacuum pump control circuit voltage with a multimeter; compare to manufacturer specifications.
Step 4: Check the vacuum pump relay and fuse; replace if faulty.
Step 5: If circuit and relay are good, test the vacuum pump motor directly; replace if it fails to operate.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended. Low vacuum can cause a hard brake pedal and reduced braking performance, increasing the risk of an accident.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for parts and labor, depending on whether the issue is a simple relay replacement or a more involved wiring repair.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.