P0474: Exhaust Pressure Sensor Circuit Intermittent
The P0474 code indicates that the Engine Control Module (ECM) has detected an intermittent signal from the exhaust pressure sensor circuit. This sensor monitors backpressure in the exhaust system, often used for diesel particulate filter (DPF) regeneration or variable geometry turbocharger (VGT) control. An intermittent fault means the signal is erratic or drops out temporarily, which can be caused by wiring issues, loose connections, or a failing sensor.
1. Most Common Causes
- Loose or corroded electrical connections at the sensor harness
- Sensor wiring shorted, open, or with damaged insulation
- Intermittent internal failure of the exhaust pressure sensor
- Soot buildup or partial blockage in the pressure sampling line
- Exhaust system leaks that alter sensor readings
- Intermittent failure of the PCM reference voltage (VREF) or ground supply
2. Symptoms You Will Notice
- Check Engine Light on
- Reduced engine performance or power loss
- Poor fuel economy
- Possible DPF regeneration issues
3. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect the exhaust pressure sensor and wiring for damage or corrosion.
Step 3: Check sensor connector for tightness and clean if necessary.
Step 4: Use a multimeter to test sensor signal voltage and compare to specifications.
Step 5: Perform a wiggle test on wiring while monitoring sensor signal to identify intermittent breaks.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is generally safe for short trips, but prolonged driving may cause reduced performance or damage to the DPF or turbocharger. It's best to diagnose and repair promptly.
How much does it cost to fix?▼
Repair costs typically range from $50 to $150 for parts and labor, depending on whether the sensor needs replacement or just a wiring repair.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.