Powertrain, generic (extended)

P20B2 Reductant Heater Coolant Control Valve Performance/Stuck Open

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P20B2 is a functional fault of the coolant valve that heats the reductant system: the circuit is intact, but temperatures do not follow the commanded valve position, most often because coolant keeps flowing while the valve should be shut. Hino uses the code in its dosing control unit and covers it in tech tip TT-16-014 for 2011–2017 conventional and 2013–2017 cab-over trucks. Most valves returned under warranty showed no defect, and a wrong DEF tank temperature input can set P20B2 falsely. Hino therefore asks to sort out any stored P205B to P205D or U02A2 first and, with the engine cold, to confirm that tank, pump and coolant temperatures agree within 8 °C (14 °F). Confirming the fault takes a drive with full warm-up.

Likely causes

Wrong DEF tank or pump temperature input misleading the valve check
Coolant valve mechanically stuck open (deposits, debris)
Valve test blocked by other stored SCR faults, valve wrongly condemned

Symptoms

  • Malfunction indicator with no other SCR fault stored
  • DEF tank temperature runs unusually high
  • Possible engine power restriction if left unrepaired

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€60–700
Time1–3 h

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

Parts involved

reductant coolant valve

Related codes

P20B1P20B3P20B4P205CP20ADP0116

References: static.nhtsa.gov, law.cornell.edu, en.wikipedia.org.