Powertrain, generic (extended)

P2D38 Hybrid/EV Battery Pack Heater Performance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P2D38 is the functional check of the traction battery heater: it was switched on, yet the pack or its coolant did not warm as expected, or the heater ran too hot. CARB asks for such a heating check wherever feasible. Toyota uses the code on the 2023 bZ4X as P2D384B, the failure type standing for over temperature; tech tip T-TT-0727-23 lists it with an illuminated MIL and asked dealers to call technical support first because the cause was still under investigation. GM's Volt shows the usual logic under its own code P1EC6: in 2011, heater on for more than 40 s with less than 9 °C rise of the pack inlet coolant; in 2014, a rise slower than 0.15 °C/s within up to 161 s while charging; both Type B over two trips. Wiring faults of heater circuits use other codes. In cold weather, charging and power may be restricted.

Likely causes

Heater element or its power switch delivering no or too little heat
Air, low coolant or a weak pump so that heat does not reach the pack sensors
Pack inlet or cell temperature sensor reading wrong, faking a missing rise or overheating
Control software that judges the heating too strictly (Toyota bZ4X case under investigation)

Symptoms

  • Malfunction indicator lamp or hybrid/EV system warning on
  • Slow charging or reduced power in cold weather
  • Battery stays cold although preconditioning was requested

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€100–2,000
Time0.5–4 h

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

Parts involved

hv battery heaterbattery pack coolant loop

Related codes

P0E15P0E19P0AFDP0C32P0A7E

References: static.nhtsa.gov, gsi.ext.gm.com, gsi.ext.gm.com, law.cornell.edu.