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DTC codes / P09xx · Transmission / P093C

P093CHydraulic Accumulator Solenoid Circuit High

P093C indicates that the powertrain control module (PCM) has detected an abnormally high voltage on the hydraulic accumulator solenoid circuit, which is used in some electro-hydraulic systems to maintain pressure for functions like stop-start or active suspension. The PCM monitors the solenoid control circuit and sets this code when the voltage exceeds the expected range, often due to a short to power, an open circuit, or a faulty solenoid.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaTransmission

Symptoms you may notice

  • Illumination of the check engine light or service vehicle soon message
  • Often no symptoms besides the warning light
  • Reduced or disabled operation of the hydraulic system, such as stop-start not engaging
  • Harsh engagement or delayed response from hydraulic components
  • In rare cases, a no-start condition if the hydraulic system is critical

Common causes, most likely first

  1. Faulty hydraulic accumulator solenoid (internal short or open coil)
  2. Short to voltage in the solenoid control circuit (wiring chafed against power wire)
  3. Open circuit in the solenoid ground or power supply
  4. Corroded or damaged electrical connector at the solenoid
  5. Failed PCM driver for the solenoid circuit (less common)
  6. Low fluid level or contaminated hydraulic fluid causing abnormal solenoid operation

How to diagnose and fix it

  1. Verify battery voltage and ensure the charging system is functioning properly
  2. Inspect the solenoid electrical connector for corrosion, loose pins, or damage
  3. Measure resistance across the solenoid coil and compare to manufacturer specification
  4. Check for short to voltage or open circuit in the control wiring between the PCM and solenoid
  5. Test the solenoid with a known-good unit or use a bidirectional scan tool to command it on and off
  6. If wiring and solenoid test good, diagnose the PCM driver circuit or replace the PCM as needed
  7. Clear codes and perform a road test to confirm the repair

Don't overlook the simple checks first

  • A loose or corroded ground connection for the hydraulic accumulator solenoid can cause a high voltage code by creating an open circuit that the PCM interprets as excessive voltage.
  • Some vehicles use the hydraulic accumulator solenoid for stop-start systems, and a failing solenoid may not produce any drivability symptoms until the system is commanded to operate.
  • A short to voltage in the control circuit can be intermittent, often caused by wiring rubbing against a hot exhaust component or sharp edge, so a wiggle test while monitoring live data is essential.
  • Replacing the solenoid without checking the PCM driver can lead to repeat failures if the driver is shorted internally, so always verify the control signal with a scope or scan tool.
  • Low hydraulic fluid level or air in the system can cause the solenoid to draw higher current, which may set a high voltage code in some monitoring strategies, so check fluid condition and level before condemning electrical parts.

Can I keep driving with P093C?

If the vehicle drives normally and the only symptom is the warning light, you can drive cautiously to a repair shop, but avoid using any systems that rely on the hydraulic accumulator, such as stop-start or active suspension features. If the vehicle exhibits reduced performance or hydraulic functions are disabled, limit driving to essential trips and have the fault diagnosed promptly.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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