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 is having trouble with a part that helps you change gears. It's like when a light switch isn't working right, so you can't turn the light on or off easily.
The P1878 code indicates a problem with the electrical circuit related to the gear selector lever, specifically the GSL4 circuit, which is reading a low voltage.
The P1878 code is triggered when the transmission control module (TCM) detects a low voltage condition in the gear selector lever circuit GSL4. This circuit is responsible for communicating the gear position to the TCM. A low voltage condition could be due to a short to ground, a faulty sensor, or a problem with the wiring or connections.
• Check Engine Light is on
• Transmission may not shift properly
• Vehicle may not start or move
• Faulty gear selector lever sensor
• Short to ground in the GSL4 circuit
• Damaged or corroded wiring or connectors
TCM: Transmission Control Module
GSL: Gear Selector Lever
• Use an OBD-II scanner to confirm the code.
• Inspect the wiring and connectors for damage or corrosion.
• Test the gear selector lever sensor for proper operation.
• Replace or repair damaged wiring or connectors.
• Replace the faulty gear selector lever sensor.
• Clear the code and test drive the vehicle to ensure the issue is resolved.
• OBD-II scanner
• Multimeter
• Basic hand tools (screwdrivers, pliers)
$150 - $400
Moderate
• Toyota Camry
• Honda Accord
• Ford Fusion
• Regularly inspect wiring for damage.
• Ensure connectors are clean and secure.
• Avoid exposure of electrical components to moisture.
Sensor Issue
• Do not ignore the Check Engine Light.
• Have the vehicle inspected by a professional if unsure about repairs.
Check with your vehicle manufacturer for warranty coverage on transmission components.
The P1878 code has been reported in vehicles with high mileage or those exposed to harsh environmental conditions.
Moderate – While the vehicle may still operate, improper gear shifting can lead to further damage.
Driving with a malfunctioning transmission can be unsafe. Address the issue promptly to avoid potential accidents.
• Vehicle in park or neutral
• Ignition on, engine off
The gear selector lever is typically located between the driver and passenger seats, connected to the transmission via a cable or electronic system.
Q: Can I drive with a P1878 code?
A: It's not recommended to drive for long periods with this code, as it can lead to further transmission issues.
Q: How do I clear a P1878 code?
A: After repairing the issue, use an OBD-II scanner to clear the code. If the problem persists, the code may return.
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