Reductant Metering Unit Temperature Sensor Circuit Intermittent/Erratic
The P20B0 code indicates an intermittent or erratic signal from the reductant metering unit temperature sensor, which monitors the temperature of the diesel exhaust fluid (DEF) in the metering unit. This sensor is part of the selective catalytic reduction (SCR) system, and a faulty signal can cause incorrect DEF injection, leading to increased emissions and potential damage to the SCR catalyst. Common causes include a defective sensor, wiring issues, or a poor electrical connection.
01. Most Common Causes
- Faulty reductant metering unit temperature sensor
- Damaged or corroded wiring/connectors in the sensor circuit
- Intermittent short or open circuit in the sensor harness
- Failed reductant metering unit (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine performance or limp mode
- Increased diesel exhaust fluid consumption
- Failed emissions test
03. Step-by-Step Diagnosis
Step 1: Scan for additional codes and record freeze frame data.
Step 2: Visually inspect the sensor and wiring for damage, corrosion, or loose connections.
Step 3: Test sensor resistance and compare to manufacturer specifications.
Step 4: Check for intermittent issues by wiggling the harness while monitoring sensor signal with a scan tool.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances with this code, as it can lead to reduced performance, increased emissions, and potential damage to the SCR system. You may experience limp mode.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for parts and labor, depending on whether the sensor or wiring needs replacement. Diagnostic fees may be extra.