Powertrain, generic (extended)

P2C18 B Camshaft Profile Actuator Position Sensor B Circuit Low Bank 1

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

A ground short in the position sensor B line on the bank 1 exhaust side sets P2C18. On GM's L3B this is the feedback wire of exhaust actuator 2. GM's table phrases it as a fault of the sensor's solenoid driver: with the output commanded on, a signal-to-ground impedance not above 0.5 ohm in four samples out of five, supply over 11 V and ignition in crank or run, stores Type A and switches on the MIL (19OBDG03D, unchanged in 25OBDG03B). As with P2C14, GM's PIT5677 and 21-NA-149 list P2C18 only as a keyword, not under the codes found on affected trucks. Areas to inspect include the harness run over the camshaft carrier cover and below the air cleaner box, plus the actuator connector. The second exhaust actuator stays inactive until the short is repaired.

Likely causes

Harness insulation damaged at the camshaft carrier cover or under the air cleaner housing
Exhaust actuator 2 shorted internally to ground
Water or oil bridging contacts in the plug

Symptoms

  • MIL comes on in the first trip
  • Exhaust profile no longer changes, small rise in fuel use

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–900
Time0.5–4 h

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

Parts involved

b camshaft profile actuator pos sensor b b1wiring harnessecm

Related codes

P2C14P2C16P2C17P2C19P2C0BP2B3A

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