What Does P099C Mean?
The TCM has detected that the shift solenoid 'G' control circuit is reading high, indicating an open circuit or short to voltage. The solenoid cannot be grounded or its control signal is being pulled high, preventing the TCM from commanding the solenoid. This results in loss of shift control for the gear associated with solenoid G.
Common Causes
35%
Open circuit in shift solenoid G winding (burned out coil)
25%
Broken wire or open connection in the solenoid G circuit
25%
Disconnected or corroded connector at transmission or TCM
15%
Short to voltage in the solenoid control wire
Diagnostic Steps
1
Step 1: Measure solenoid G resistance at the transmission connector. An OL (open line) reading confirms a burned-out solenoid. Expected is 10-25 ohms.
2
Step 2: Verify continuity of both the control wire and ground wire from the transmission case connector to the TCM. Both should show less than 1 ohm resistance.
3
Step 3: Inspect the transmission case pass-through connector and TCM connector for damaged, backed-out, or corroded pins.
4
Step 4: Use a bidirectional scan tool to command solenoid G on/off while monitoring amperage. Zero current with the solenoid connected indicates an open in the circuit path.
5
Step 5: Check for voltage on the solenoid control wire with the connector unplugged. Any voltage present (besides TCM driver voltage) indicates a short to a power source.
Estimated Repair Cost
$200 - $850
Parts + labor, varies by vehicle and location
The TCM has detected that the shift solenoid 'G' control circuit is reading high, indicating an open circuit or short to voltage. The solenoid cannot be grounded or its control signal is being pulled high, preventing the TCM from commanding the solenoid. This results in loss of shift control for the...
The most common cause of P099C (Shift Solenoid "G" Control Circuit High) is: Open circuit in shift solenoid G winding (burned out coil)
Typical repair costs for P099C range from $200 to $850, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Loss of specific gear engagement and likely limp mode operation. Safe for short-distance driving to a shop but do not continue normal driving.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P099C to identify the root cause.
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Quick Info
Category
Powertrain
System
Transmission Shift Control
Difficulty
Type
Generic (SAE)
Recommended Tools
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