Powertrain, generic (extended)

P2B91 Turbocharger/Supercharger B Temperature Sensor Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P2B91 is stored when temperature sensor B delivers a signal above its permitted window. By far the most frequent reason is a broken current path: an unplugged or corroded connector, a cracked wire or an element that has burned open, which pulls the input up to its reference voltage. A short to the 5 V supply or to battery voltage has the same effect. For an NTC part this looks like severe cold, for a platinum resistor like severe heat; the sensor patent US8328419B2 from Heraeus explains why lead strain and heat cycling make such breaks a known weak point. No manufacturer publishes this code. Per CARB 13 CCR 1968.2 (e)(15) it is kept separate from the low fault P2B90 and the general circuit code P2B8F. Sensor A uses P2B70.

Likely causes

Signal or ground wire open, connector unplugged or corroded
Sensor element or its lead wires broken by heat cycling
Signal wire shorted to the 5 V reference or battery voltage

Symptoms

  • Warning lamp with stored code
  • Sensor B stuck at an end value in live data

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

P2B8FP2B90P2B92P2B70

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