Powertrain, generic (extended)

P20B0 Reductant Metering Unit Temperature Sensor Circuit Intermittent/Erratic

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P20B0 flags a metering unit temperature signal that jumps or drops out for brief moments instead of failing steadily. Housing, pump and fluid store a lot of heat, so the real temperature cannot change in leaps; the software treats such steps as a signal defect. Loose terminals, a harness rubbing against the frame near the tank and connectors exposed to road splash and thermal cycling are the main suspects. Since the fault comes and goes, it may well be inactive at the moment of inspection, and wiggling the harness while watching live data helps more than a single resistance reading. No manufacturer documents P20B0 publicly, so the actual jump limits remain unknown.

Likely causes

Loose or spread terminal in the module connector
Harness chafing intermittently against frame or tank bracket
Moisture entering the connector during wet or freezing conditions

Symptoms

  • Warning lamp that comes and goes
  • Temperature value jumping in live data
  • Fault often not reproducible in the workshop

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–1,500
Time1–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

reductant metering unitreductant metering temp sensor

Related codes

P20ACP20ADP20AEP20AFP205E

References: law.cornell.edu, picoauto.com.