Powertrain, generic (extended)

P2E68 System Too Lean During Cylinder Deactivation Bank 1

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

P2E68 is a fuel trim fault that is judged only while cylinders are shut off: in that mode bank 1 needs more fuel correction than allowed. GM uses it on its 4.2-litre twin-turbo V8 (LTA, table 19OBDG07): the engine learns a separate multiplicative long-term trim for deactivation mode, and the code sets when that factor for bank 1 rises above 1.23 and has been steady for at least 10 s; Type B, MIL after two trips. Enables include coolant at 54.8 °C or more, intake air under 90 °C and no wide-open throttle. Full-engine lean faults use other codes, such as P2177. On that engine half the cylinders run in this mode, two per bank. A Ford patent explains why a faulty valve deactivator shows up as a bank-specific trim shift.

Likely causes

Restricted injector on one of the cylinders that keep firing on bank 1
Unmetered air entering bank 1 (intake leak, seal, PCV)
Deactivating rocker or lifter on bank 1 not holding the valves shut, pumping air into the exhaust
Bank 1 oxygen sensor reading biased rich

Symptoms

  • Check engine light after two trips
  • Slight shake or surge at light cruise when cylinders are shut off
  • Cylinder deactivation may be used less often

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–2,000
Time1–8 h

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

Parts involved

fuel injectorsdeactivation solenoidsintake system

Related codes

P2E6AP2E69P2177P0171P3400

References: gsi.ext.gm.com, law.cornell.edu, image-ppubs.uspto.gov, gm-efi.com.