What Does P0999 Mean?
The TCM has detected that the shift solenoid 'F' control circuit is reading high, indicating an open circuit or short to battery voltage. The solenoid cannot be properly grounded or controlled, preventing the TCM from modulating shift pressure through this circuit. This often results in default shift pressure and harsh engagement.
Common Causes
35%
Open circuit in shift solenoid F winding (burned out coil)
25%
Broken or disconnected wire in the solenoid F control circuit
25%
Corroded or disconnected connector at the transmission case or TCM
15%
Signal wire shorted to battery voltage in the harness
Diagnostic Steps
1
Step 1: Measure solenoid F resistance at the transmission case connector. An open-line reading (OL) confirms a burned-out solenoid coil. Expected resistance is typically 10-25 ohms.
2
Step 2: If resistance is in spec at the solenoid, check continuity from the transmission case connector back to the TCM on both the control and ground wires. Resistance should be less than 1 ohm on each wire.
3
Step 3: Inspect connectors at both the transmission case pass-through and the TCM for backed-out pins, corrosion, or ATF contamination. Ensure locking tabs are fully engaged.
4
Step 4: With the solenoid disconnected, measure voltage on the TCM control wire with KOEO. It should show near battery voltage (solenoid high-side power). If absent, the TCM driver or power feed is faulty.
5
Step 5: Command solenoid F on/off with a bidirectional scan tool while monitoring current. Zero current draw with a functioning solenoid confirms an open in the harness between the TCM and solenoid.
Estimated Repair Cost
$200 - $850
Parts + labor, varies by vehicle and location
The TCM has detected that the shift solenoid 'F' control circuit is reading high, indicating an open circuit or short to battery voltage. The solenoid cannot be properly grounded or controlled, preventing the TCM from modulating shift pressure through this circuit. This often results in default shif...
The most common cause of P0999 (Shift Solenoid "F" Control Circuit High) is: Open circuit in shift solenoid F winding (burned out coil)
Typical repair costs for P0999 range from $200 to $850, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Expect harsh shifts or inability to engage certain gears. The vehicle may enter limp mode. Safe for short distances to a repair facility.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0999 to identify the root cause.
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Quick Info
Category
Powertrain
System
Transmission Shift Control
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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