Powertrain, generic · Transmission

P093C Hydraulic Accumulator Solenoid Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

The control circuit of the hydraulic accumulator solenoid reads high, typically a control wire shorted to battery voltage so the driver cannot switch the valve as commanded. No manufacturer documents P093C publicly. GM covers the same fault on its surge accumulator solenoid with P171C: failed short to voltage when the circuit impedance criterion of 0.5 Ohm is met in 6 of 8 samples, Type B with MIL after two trips. GM's patent on an accumulator with solenoid valve shows how the valve holds or releases the stored fluid. P093A is the open circuit, P093B the low fault and P093D the performance fault. Stop-start is usually disabled; a valve that never closes cannot keep the accumulator charged during an auto-stop.

Likely causes

Solenoid control wire shorted to battery voltage
Damaged internal transmission harness or lead frame
Output driver in the control module failed

Symptoms

  • Warning light on (after repeated detection)
  • Engine stop-start no longer active
  • Jolt when pulling away after a restart

Repair estimate

DifficultyHardWorkshop job
Parts and labour€150–1,200
Time1–5 h

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

Parts involved

hydraulic accumulator solenoidwiring harnesstcm

Related codes

P093AP093BP093D

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