Powertrain, generic (extended)

P2BB5 Engine Coolant Temperature Sensor 5 Circuit Intermittent/Erratic

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P2BB5 is the erratic-signal code for coolant sensor 5. Unlike the hard circuit faults P2B2D and P2B2E, the reading here stays within the valid range but changes faster than the sensor's thermal inertia allows, which betrays a contact that briefly opens or shorts. GM has carried the code in both its 2019 L3B/common tables (19OBDG03D) and its 2025 ECM tables (25OBDG03B) with the same rule: limits for the next sample are calculated from the previous one, and violations for 5 s within a 6 s window store P2BB5 as Type B, MIL after two trips. GM bulletin 21-NA-149 lists it among the codes a chafed engine harness causes on 2019–2021 Silverado and Sierra 1500 pickups. Wiggle-test the harness while watching live data before replacing the sensor.

Likely causes

Chafed engine harness with intermittent contact in the sensor 5 wires
Loose, spread or corroded connector terminal
Sensor element breaking intermittently

Symptoms

  • MIL on after the second trip
  • Sensor 5 value spikes in live data
  • Often stored together with other harness-related codes

Repair estimate

DifficultyMediumDIY possible
Parts and labour€30–400
Time0.5–3 h

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

Parts involved

engine coolant temperature sensor 5wiring harnessecm

Related codes

P2B2BP2B2CP2B2DP2B2EP2BB4P2BBA

References: gsi.ext.gm.com, gsi.ext.gm.com, static.nhtsa.gov.