Powertrain, generic (extended)

P2B90 Turbocharger/Supercharger B Temperature Sensor Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P2B90 means the signal of temperature sensor B has dropped below the lowest value the engine computer accepts. What that says about temperature depends on the element: an NTC thermistor loses resistance when hot, so a low signal reads as extreme heat, whereas a platinum resistor of the kind Heraeus patented for turbo protection (US8328419B2) gains resistance with heat, so a low signal reads as extreme cold. Electrically both point the same way: a signal wire touching ground or a shorted element. No manufacturer publishes this code, so the sensor type of a given engine must be taken from its service data. CARB 13 CCR 1968.2 (e)(15) keeps low and high faults apart. The high counterpart is P2B91, the matching code for sensor A is P2B6F.

Likely causes

Signal wire shorted to ground, for example melted insulation
Sensor element shorted internally
Faulty input stage in the engine computer

Symptoms

  • Warning lamp with stored code
  • Sensor B shows a fixed extreme value even on a cold engine

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€60–450
Time0.5–2.5 h

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

Parts involved

turbocharger b temperature sensorwiring harnessecm

Related codes

P2B8FP2B91P2B92P2B6F

References: law.cornell.edu, patents.google.com, en.wikipedia.org.