P2728 marks the circuit of solenoid E as working but not plausible. GM uses it in two ways. On the Allison 1000 (16OBDG08, 17OBDG04) the TCM compares desired with actual current on PCS 1; a gap of at least 0.5 A in 10 of fewer than 20 samples sets a Type A fault with MIL. On the T76 six-speed table of 2016, where valve E serves the 1-2-3-4 clutch, an invalid voltage flag for 4.4 of 5 s sets it without MIL. Bulletin PI0893 explains the second case for 2013 vehicles with the 6T70/6T75: as a Type C history code next to P2719 and P0965 it can appear falsely with fluid between -0.5 and 0 °C in Park or Neutral and needs no parts. MIL behaviour therefore depends on the gearbox.
Medium severity. Can I keep driving?Drive as little as possible and gently. If the transmission slips or stays in one gear, go slowly to a repair shop or call for a tow truck.
Symptoms
- MIL on Allison-equipped trucks
- History code without symptoms on GM six-speeds
- Firm shifts if pressure control is degraded
Most likely causes
- Coil current deviating from command (resistance change, poor contact)
- False history code near 0 °C fluid temperature (GM 6T70/6T75)
- Unstable supply voltage to the TCM
- Worn solenoid E
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
- It can trigger limp mode.
- It affects emissions.
What each character of P2728 means
- P: Powertrain: engine and transmission
- 2: Generic code: same on every make
- 7: Transmission
- 28: Specific fault in that system
Frequently asked questions
Can I keep driving with code P2728?
Drive as little as possible and gently. If the transmission slips or stays in one gear, go slowly to a repair shop or call for a tow truck.
What causes code P2728?
The most common causes are: coil current deviating from command (resistance change, poor contact); false history code near 0 °C fluid temperature (GM 6T70/6T75); unstable supply voltage to the TCM.
Related codes
- P2719Pressure Control Solenoid D Control Circuit Range/Performance
- P2727Pressure Control Solenoid E Control Circuit/Open
- P2729Pressure Control Solenoid E Control Circuit Low
- P2730Pressure Control Solenoid E Control Circuit High
- P0965Pressure Control Solenoid B Control Circuit Range/Performance
Sources
- gsi.ext.gm.com: 16OBDG08 Transmission Diagnostics
- gsi.ext.gm.com: 16OBDG03 Transmission Diagnostics
- static.nhtsa.gov: MC 10133139 9999
- gsi.ext.gm.com: 17OBDG04 Transmisson Diagnostics
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.