Powertrain, generic (extended)

P2D56 Hybrid/EV Battery Pack Coolant Temperature Sensor C Circuit Intermittent/Erratic

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

P2D56 points to a coolant temperature signal from sensor C that jumps around faster than liquid in the battery loop can really change temperature, while mostly staying inside the electrical limits. No manufacturer documents P2D56 publicly. GM runs such a test for sensor A as P0C46 in table 19OBDG01: every 100 ms the step to the previous inlet reading is taken, ten absolute steps are summed, and a sum above 64 °C counts as a failure; 4 s within 5 s set a Type B code, and the test pauses while the hard faults P0C44 or P0C45 are active. For sensor B, Volvo's TJ 36929 notes that P0CD900 after charging in air above 20 °C can be a false detection cured by software 3.2.4. CARB requires circuit continuity checks. Loose pins and moving harnesses are the usual suspects.

Likely causes

Loose or corroded terminal in the sensor C connector
Harness rubbing or moving with the battery, causing brief interruptions
Detection logic reacting to normal conditions (software update)

Symptoms

  • Warning light that comes and goes
  • Sensor C value jumps in live data, especially when wiggling the harness
  • Usually no noticeable driveability change

Repair estimate

DifficultyHardWorkshop job
Parts and labour€80–700
Time0.5–4 h

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

Parts involved

hv battery pack coolant temp sensor cwiring harnessbms

Related codes

P2D52P2D53P0C46P0CD9P2E78

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