Powertrain, generic (extended)

P2B2D Engine Coolant Temperature Sensor 5 Circuit Low

Check engine lightOn

EmissionsRelevant

Drive cycleNot required

Limp modeNo

A low signal from coolant sensor 5 means its NTC resistance has collapsed, which the engine computer would read as an impossibly hot engine; a grounded signal wire or a shorted element is the usual reason. GM documents P2B2D in its configurable temperature input system: the sensor 5 channel fails when its resistance drops below 47.5 Ω in the 2019 L3B tables or 55 Ω in the 2025 ECM tables, a value tied to roughly 150 °C, for 5 s within a 6 s window; Type B, MIL on the second trip. GM bulletin 21-NA-149 lists P2B2D among the codes that chafed engine harnesses produce on 2019–2021 Silverado and Sierra 1500 trucks. NTN-SNR calls it signal too low for sensor 5. Fans may run at full speed until repair. P2B2E is the reverse fault.

Likely causes

Signal wire grounded, for example by a chafed harness

Shorted sensor 5 element

Engine control module input fault

Symptoms

MIL after two trips
Radiator fans running constantly at high speed
Other harness-related codes stored at the same time

Repair estimate

DifficultyEasyDIY possible

Parts and labour€30–300

Time0.3–2 h

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

Parts involved

engine coolant temperature sensor 5wiring harnessecm

Related codes

P2B2E P2B2B P2B2C P2BB5 P2AFE P2184

References: gsi.ext.gm.com, gsi.ext.gm.com, static.nhtsa.gov, ntn-snr.com.