Fault Family System: Powertrain (P-Codes) 21 SAE Codes

HV Battery Pack Coolant Temp Sensor

Diagnostic & Technical Explanation

Code P0C42 sets when the control module detects an implausible reading from the sensor measuring coolant temperature at the HV battery pack's liquid-cooling manifold — the value disagrees with the pack's thermistor-string cell-median reading or with the coolant pump's commanded flow rate. Because the manifold sits low in the pack enclosure, the most common physical causes are a coolant leak at the sensor's O-ring seat, which can also introduce a slow drift as coolant level drops, a trapped air pocket at the manifold high point that makes the reading swing implausibly fast, and a thermistor element that has drifted internally. Unlike the pack's cell-group thermistors, this sensor sits in liquid coolant rather than potted against a busbar, so a coolant-side fault points here, not into the module stack.

These 21 diagnostic trouble codes share one detection mechanism and one repair path, which is why MechanicDB groups them into a single authored fault family rather than repeating the same explanation 21 times.

Codes in this family (21)

Code	Definition	Repair coverage
P0C42	Hybrid/EV Battery Pack Coolant Temperature Sensor A Circuit	4 ranked fixes
P0C43	Hybrid/EV Battery Pack Coolant Temperature Sensor A Circuit Range/Performance	4 ranked fixes
P0C44	Hybrid/EV Battery Pack Coolant Temperature Sensor A Circuit Low	4 ranked fixes
P0C45	Hybrid/EV Battery Pack Coolant Temperature Sensor A Circuit High	4 ranked fixes
P0C46	Hybrid/EV Battery Pack Coolant Temperature Sensor A Circuit Intermittent/Erratic	4 ranked fixes
P0CD5	Hybrid/EV Battery Pack Coolant Temperature Sensor B Circuit	4 ranked fixes
P0CD6	Hybrid/EV Battery Pack Coolant Temperature Sensor B Circuit Range/Performance	4 ranked fixes
P0CD7	Hybrid/EV Battery Pack Coolant Temperature Sensor B Circuit Low	4 ranked fixes
P0CD8	Hybrid/EV Battery Pack Coolant Temperature Sensor B Circuit High	4 ranked fixes
P0CD9	Hybrid/EV Battery Pack Coolant Temperature Sensor B Circuit Intermittent/Erratic	4 ranked fixes
P2D2B	Hybrid/EV Battery Pack Coolant Temperature Sensor A/B Correlation	4 ranked fixes
P2D52	Hybrid/EV Battery Pack Coolant Temperature Sensor C Circuit	4 ranked fixes
P2D53	Hybrid/EV Battery Pack Coolant Temperature Sensor C Circuit Range/Performance	4 ranked fixes
P2D54	Hybrid/EV Battery Pack Coolant Temperature Sensor C Circuit Low	4 ranked fixes
P2D55	Hybrid/EV Battery Pack Coolant Temperature Sensor C Circuit High	4 ranked fixes
P2D56	Hybrid/EV Battery Pack Coolant Temperature Sensor C Circuit Intermittent/Erratic	4 ranked fixes
P2E74	Hybrid/EV Battery Pack Coolant Temperature Sensor D Circuit	4 ranked fixes
P2E75	Hybrid/EV Battery Pack Coolant Temperature Sensor D Circuit Range/Performance	4 ranked fixes
P2E76	Hybrid/EV Battery Pack Coolant Temperature Sensor D Circuit Low	4 ranked fixes
P2E77	Hybrid/EV Battery Pack Coolant Temperature Sensor D Circuit High	4 ranked fixes
P2E78	Hybrid/EV Battery Pack Coolant Temperature Sensor D Circuit Intermittent/Erratic	4 ranked fixes

What this page does not show

This page publishes the fault mechanism and the code index. The licensed dataset adds, for every one of the 15,886 codes, the full authored repair set (56,729 procedures in total) with the fields deliberately withheld here:

Procedures 2..n after the first-listed procedure
Aftermarket parts cost ranges in USD (est_parts_cost_min/max_usd)
Professional labor-hour estimates (est_labor_hours)
Step-by-step diagnostic and repair instructions
Replacement-part mappings and catalog lookups
6,637 manufacturer-specific OEM codes across 32 makes ($149 tier)

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