Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means that a part in your car that helps it change gears is getting too much power. It's like when you plug in a lamp and it gets too much electricity.
The vehicle's transmission control module has detected a high voltage condition in the circuit that controls the shift solenoid G.
The P099C code indicates that the transmission control module (TCM) has detected an abnormally high electrical signal in the shift solenoid G control circuit. This solenoid is responsible for controlling the flow of transmission fluid to change gears. A high circuit condition could be due to a short to power or an open circuit.
• Check Engine Light is on
• Transmission may not shift properly
• Poor fuel economy
• Faulty shift solenoid G
• Wiring issues such as shorts or open circuits
• Faulty transmission control module (TCM)
Transmission Control Module (TCM): A computer that controls the operation of the transmission.
Shift Solenoid: An electromechanical device that controls the flow of transmission fluid.
• Use an OBD-II scanner to confirm the code.
• Inspect the wiring and connectors related to shift solenoid G.
• Test the shift solenoid G for proper operation.
• Repair or replace any damaged wiring or connectors.
• Replace the shift solenoid G if it is faulty.
• Replace or reprogram the TCM if necessary.
• OBD-II scanner
• Multimeter
• Basic hand tools
$150 - $400
Moderate
• Ford F-150
• Chevrolet Silverado
• Toyota Camry
• Regular transmission fluid changes
• Routine inspection of transmission wiring
• Avoiding harsh driving conditions
Transmission Control System
• Do not ignore the Check Engine Light.
• Get the vehicle inspected by a professional as soon as possible.
Check with your vehicle manufacturer for warranty coverage on transmission components.
This code has been reported in vehicles with higher mileage or those that have experienced harsh driving conditions.
Moderate – Address the issue soon to prevent further transmission damage.
Driving with a faulty transmission can be dangerous and may lead to further damage.
• Vehicle at operating temperature
• Transmission in drive
The shift solenoid G is located inside the transmission, typically accessible by removing the transmission pan.
Q: Can I drive with a P099C code?
A: It's not recommended to drive for long periods with this code, as it can lead to further transmission damage.
Q: How is a shift solenoid tested?
A: A shift solenoid can be tested using a multimeter to check for proper resistance and operation.
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