AutoCodes – Chevrolet – P18C9 Chevrolet

P18C9 Chevrolet Code - Gear Position Sensor Gear Ratio Not Plausible

Quick Answer

The gear position sensor is a switching transistor mounted to the top of the transmission extension housing. Common causes include Faulty Gear Position Sensor, Gear Position Sensor harness is open or shorted, Gear Position Sensor circuit poor electrical connection. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: P18C9 Chevrolet indicates Gear Position Sensor Gear Ratio Not Plausible.
Common causes: Common causes include Faulty Gear Position Sensor, Gear Position Sensor harness is open or shorted, Gear Position Sensor circuit poor electrical connection.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 3,568

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Feb 05, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P18C9 Chevrolet Description

The gear position sensor is a switching transistor mounted to the top of the transmission extension housing. The four wire sensor interfaces directly with the Engine Control Module (ECM). The ECM supplies 5 V to the gear position sensor on a 5 V reference circuit and also provides a ground path on a low reference circuit. The sensor provides a Pulse Width Modulated (PWM) duty cycle to the ECM on two signal circuits that is proportional to the linear and radial position of the corresponding magnet assembly mounted to the shift shaft. The vehicle uses the gear position sensor information primarily for Active Rev Matching and Active Fuel Management. The ECM monitors the sensor signal input for an incorrect neutral condition.

OBDII Code P18C9 Chevrolet - Gear Position Sensor Gear Ratio Not Plausible - AutoCodes.com — P18C9 Chevrolet Code - Gear Position Sensor Gear Ratio Not Plausible

What does this mean?

What are the Possible Causes of the DTC P18C9 Chevrolet?

Faulty Gear Position Sensor
Gear Position Sensor harness is open or shorted
Gear Position Sensor circuit poor electrical connection

How to Fix the DTC P18C9 Chevrolet?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P18C9 Chevrolet code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P18C9 Chevrolet Code

1. What are the common symptoms of OBDII code P18C9 in a Chevrolet related to the Gear Position Sensor Gear Ratio Not Plausible?

- Common symptoms include rough shifting, erratic transmission behavior, and the transmission staying in one gear.

2. What can cause the Gear Position Sensor Gear Ratio Not Plausible code (P18C9) in a Chevrolet?

- The code P18C9 can be triggered by a faulty gear position sensor, damaged wiring, or issues with the transmission control module.

3. How serious is the P18C9 code related to the Gear Position Sensor Gear Ratio Not Plausible in a Chevrolet?

- Ignoring the P18C9 code can lead to transmission problems, potential damage to the transmission, and unsafe driving conditions.

4. How can I diagnose the P18C9 code in my Chevrolet related to the Gear Position Sensor Gear Ratio Not Plausible?

- Diagnosing the P18C9 code involves using a scan tool to read the trouble codes, checking the gear position sensor, inspecting the wiring, and testing the transmission control module.

5. Can I continue driving my Chevrolet with the P18C9 code related to the Gear Position Sensor Gear Ratio Not Plausible?

- It is not recommended to drive your Chevrolet with the P18C9 code as it can cause further damage to the transmission and lead to potential safety hazards.

6. What are some repair tips for fixing the P18C9 code in a Chevrolet?

- Repair tips include checking and replacing the gear position sensor, repairing any damaged wiring, and resetting the transmission control module.

7. How much does it typically cost to repair the P18C9 code in a Chevrolet related to the Gear Position Sensor Gear Ratio Not Plausible?

- The cost of repairing the P18C9 code can vary depending on the exact cause of the issue, but it may range from $200 to $600 for parts and labor.

8. Can a DIY enthusiast fix the P18C9 code related to the Gear Position Sensor Gear Ratio Not Plausible in a Chevrolet?

- While some DIY enthusiasts may have the skills to diagnose and repair the P18C9 code, it is recommended to consult a professional mechanic due to the complexity of transmission-related issues.

9. How long does it take to repair the P18C9 code in a Chevrolet?

- The repair time for the P18C9 code can vary depending on the extent of the issue, but it typically takes a few hours to a full day to diagnose and fix the problem.

10. Is the P18C9 code specific to Chevrolet vehicles, or can it occur in other car makes and models?

- The P18C9 code related to the Gear Position Sensor Gear Ratio Not Plausible can occur in other car makes and models with similar transmission systems and gear position sensors.