Turbocharger Boost Sensor B Circuit High
The P0242 code indicates that the Engine Control Module (ECM) has detected a voltage signal from the turbocharger boost sensor 'B' that is higher than the expected range. This sensor monitors boost pressure and sends a voltage signal to the ECM. A high voltage reading suggests a short to power, faulty sensor, or wiring issues. This can lead to incorrect boost control, reduced engine performance, and potential turbocharger damage.
1. Most Common Causes
- Faulty turbocharger boost sensor B
- Short to voltage in sensor circuit
- Damaged wiring or connector
- ECM internal fault (rare)
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine power or limp mode
- Poor acceleration
- Excessive black smoke from exhaust
3. Step-by-Step Diagnosis
Step 1: Scan for additional codes and record freeze frame data.
Step 2: Visually inspect the boost sensor B connector and wiring for damage, corrosion, or shorts.
Step 3: Using a multimeter, check the sensor signal voltage at idle (should be ~0.5-1.5V) and under boost (up to 4.5V). If voltage is near 5V constant, suspect short to power.
Step 4: Compare readings with a known good sensor or test sensor resistance per manufacturer specs.
Step 5: If sensor and wiring are okay, test the ECM's 5V reference and ground circuits.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as the engine may enter limp mode, reducing power and potentially causing turbocharger damage. Have it diagnosed promptly.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for a new boost sensor, plus labor if installed by a shop. DIY replacement can save labor costs.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.