Powertrain, generic · Ignition system or misfire

P0388 Crankshaft Position Sensor B Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

Some engines have a second crankshaft sensor or a second track on the tone wheel – GM's 3.4/3.5/3.8-litre V6 use the low resolution track of a dual Hall sensor, the Honda 3.5-litre in the Saturn Vue Redline a second sensor – which the engine module checks against sensor A or the camshaft. By its J2012 name P0388 means the signal of sensor B stays above its upper limit – with a Hall sensor typically an open signal wire held high by the module's pull-up, or a short to positive. No manufacturer document available to us uses P0388: the engines with a sensor B report its electrical faults under P0385 and implausible signals under P0386. The description therefore follows the J2012 name, these component sources and CARB's monitoring requirement for crank angle sensors. The engine usually keeps running on sensor A; longer cranking is possible.

Likely causes

Signal wire of sensor B open or connector corroded or loose
Signal wire shorted to positive or reference voltage
Sensor ground open
Sensor B faulty internally
Engine module input

Symptoms

  • Check engine light on
  • Longer cranking or starting problems
  • Possibly rough running or misfire
  • Often no noticeable symptoms while sensor A takes over

Repair estimate

DifficultyMediumDIY possible
Parts and labour€60–350
Time0.5–2.5 h

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

Parts involved

crankshaft position sensor bcrankshaft tone wheelsensor wiringengine control module

Related codes

P0385P0386P0387P0389P0338

References: law.cornell.edu, gsi.ext.gm.com, gsi.ext.gm.com.