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 the car's computer has detected a problem with the circuit that controls an electric pump that helps move the transmission fluid. It's like when a toy's battery is too strong and makes it run too fast.
The P2799 code is triggered when the powertrain control module (PCM) detects a high voltage condition in the control circuit of the auxiliary transmission fluid pump A.
The auxiliary transmission fluid pump is responsible for circulating transmission fluid when the engine is off or when additional cooling is needed. A 'high' condition indicates that the voltage in the circuit is higher than expected, which can be caused by wiring issues, a faulty pump, or a malfunctioning PCM.
• Check Engine Light is on
• Transmission overheating
• Reduced transmission performance
• Faulty auxiliary transmission fluid pump
• Short circuit in the wiring
• Malfunctioning powertrain control module (PCM)
PCM: Powertrain Control Module
OBD-II: On-Board Diagnostics II
• Use an OBD-II scanner to confirm the code.
• Inspect the wiring and connectors for damage or corrosion.
• Test the auxiliary transmission fluid pump for proper operation.
• Repair or replace damaged wiring or connectors.
• Replace the faulty auxiliary transmission fluid pump.
• Reprogram or replace the PCM if necessary.
• OBD-II scanner
• Multimeter
• Wiring repair kit
$200 - $600
Moderate
• Toyota Prius
• Ford Fusion Hybrid
• Chevrolet Volt
• Regular maintenance of the transmission system
• Check and replace transmission fluid as needed
• Inspect wiring for wear and tear regularly
Sensor Issue
• Avoid driving the vehicle until the issue is fixed to prevent further damage.
• Consult with a certified mechanic for accurate diagnosis and repair.
Check with your vehicle manufacturer for warranty coverage on transmission components.
This code has become more common with the rise of hybrid and electric vehicles that use electric pumps for transmission fluid circulation.
Moderate – Should be addressed soon to avoid transmission damage.
Driving with this issue can lead to transmission damage, which may be costly to repair.
• Vehicle at operating temperature
• Engine off
The auxiliary transmission fluid pump is typically located near the transmission housing.
Q: Can I drive with a P2799 code?
A: It's not recommended to drive with this code as it can lead to transmission damage.
Q: How do I reset the P2799 code?
A: After fixing the issue, use an OBD-II scanner to clear the code.
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