Powertrain, generic · Hybrid propulsion

P0C39 DC/DC Converter Temperature Sensor A Range/Performance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P0C39 is the plausibility check of DC/DC converter temperature sensor A: its reading lies within the electrical range but does not fit the converter's operating state or a second sensor. FCA uses it on the 2021 Ram 1500 with the 3.6 litre eTorque mild hybrid, where the code is called temperature sensor 1 performance. Bulletin 08-037-21 updates the HCP software and changes this code from a two-trip to a one-trip DTC, so the MIL can come on after a single fault. Sensor B, sensor 2 at Ram, has the matching code P0C3E. CARB requires rationality checks for such inputs. A drifting sensor or poor thermal contact is typical; outright circuit faults are reported as P0C38, P0C3A or P0C3B instead.

Likely causes

Outdated hybrid control software (Ram 1500 eTorque, bulletin 08-037-21)
Sensor A drifting or with poor thermal contact to the power stage
Uneven cooling of the converter making the readings disagree

Symptoms

  • MIL, after one trip with updated Ram software
  • Mild hybrid assist or 12 V supply reduced

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€80–1,800
Time0.5–4 h

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

Parts involved

dcdc converter temp sensor awiring harnessdcdc converter

Related codes

P0C38P0C3AP0C3BP0C3CP0C3EP0E59

References: static.nhtsa.gov, law.cornell.edu.