Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means there's a problem with the car's computer detecting the right gear ratio when shifting from the 6th gear. It's like the car is confused about which gear it's in.
The vehicle's transmission control module (TCM) monitors the gear ratios during shifts. If the expected gear ratio is not achieved when shifting from 6th gear, this code is triggered.
P18D6 is triggered when the TCM detects that the actual gear ratio does not match the expected gear ratio when shifting from the 6th gear. This could be due to mechanical issues in the transmission or electronic control problems.
• Check Engine Light is on
• Transmission slipping
• Poor fuel economy
• Faulty transmission control module
• Mechanical failure in the transmission
• Faulty speed sensors
Transmission Control Module (TCM): A computer that controls the transmission's functions.
Gear Ratio: The ratio of the rotational speeds of two or more interlocking gears.
• Check for other related codes
• Inspect transmission fluid level and condition
• Test drive the vehicle to observe shifting behavior
• Replace or reprogram the transmission control module
• Repair or replace faulty speed sensors
• Inspect and repair transmission internals
• OBD-II scanner
• Transmission fluid dipstick
• Multimeter
$500 - $2000
Difficult
• Chevrolet Silverado
• GMC Sierra
• Cadillac Escalade
• Regular transmission fluid changes
• Routine transmission inspections
• Avoid aggressive driving
Transmission Issue
• Avoid driving the vehicle until repaired
• Consult with a certified mechanic
Check with the vehicle manufacturer for powertrain warranty coverage.
This code has been more common in vehicles with high mileage or those that frequently tow heavy loads.
High – Driving with this issue can lead to further transmission damage.
Ignoring this issue can lead to unsafe driving conditions and potential legal liabilities if the vehicle fails to operate safely.
• Vehicle at operating temperature
• Test drive on a level road
The transmission control module is usually located near the transmission or under the hood.
Q: Can I drive with a P18D6 code?
A: It's not recommended as it can cause further damage to the transmission.
Q: How is the P18D6 code diagnosed?
A: A mechanic will use an OBD-II scanner to retrieve the code and perform tests on the transmission system.
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