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DTC codes / P09xx · Transmission / P099E

P099EShift Solenoid H Control Circuit Low

P099E indicates that the transmission control module (TCM) has detected an abnormally low voltage or current on the control circuit for shift solenoid H, which is one of the solenoids that manages hydraulic pressure for gear shifts. The TCM monitors the circuit and sets this code when the signal falls below the expected threshold, often due to a short to ground, a faulty solenoid, or wiring issues.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaTransmission

Symptoms you may notice

  • Illumination of the check engine light or transmission warning light
  • Harsh or delayed gear shifts, especially when the affected solenoid is commanded
  • Transmission may enter limp mode, limiting gear selection to a single gear
  • Slipping or flaring during shifts
  • Often no symptoms besides the warning light, especially if the fault is intermittent

Common causes, most likely first

  1. Faulty shift solenoid H (internal short or open coil)
  2. Damaged or chafed wiring in the solenoid control circuit, causing a short to ground
  3. Corroded or loose electrical connector at the solenoid or TCM
  4. Transmission fluid contamination or low fluid level affecting solenoid operation
  5. Failed transmission control module (TCM) or internal driver circuit
  6. Valve body issues causing abnormal pressure that stresses the solenoid

How to diagnose and fix it

  1. Check transmission fluid level and condition; top off or replace if contaminated
  2. Inspect the solenoid H electrical connector and wiring for damage, corrosion, or loose pins
  3. Measure resistance of solenoid H and compare to manufacturer specifications
  4. Test the control circuit for a short to ground using a multimeter and wiring diagram
  5. If the solenoid is faulty, replace it and clear the code
  6. If wiring is damaged, repair or replace the affected section
  7. If the TCM is suspected, perform pinpoint tests before replacement

Don't overlook the wiring harness

  • A short to ground in the solenoid control circuit is a common cause that is often missed when technicians focus solely on the solenoid itself.
  • Intermittent faults can be caused by vibration or heat affecting the wiring, so wiggle tests and road tests may be necessary to reproduce the issue.
  • The code does not always mean the solenoid is defective; a faulty TCM driver or contaminated fluid can also set it.
  • Some vehicles use a single solenoid for multiple functions, so a failure may affect more than one gear, leading to misdiagnosis of a mechanical transmission problem.

Can I keep driving with P099E?

If the vehicle is in limp mode or shifting poorly, avoid driving at high speeds or under heavy load and seek service soon. Continuing to drive with harsh shifts can damage the transmission, but if the only symptom is the warning light, you may drive cautiously to a repair shop.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

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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