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P18C5 Buick Code - Gear Position Sensor Circuit 1 High Voltage

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
P18C5 Buick indicates Gear Position Sensor Circuit 1 High Voltage.
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 782
How popular is this code, among other codes? Low
What is this?
Table of contents Created and updated by William Orellana on Feb 05, 2020
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Code P18C5 Buick 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 radial position signal 1 circuit for low and high voltage conditions.
OBDII Code P18C5 Buick - Gear Position Sensor Circuit 1 High Voltage - AutoCodes.com
P18C5 Buick Code - Gear Position Sensor Circuit 1 High Voltage
What does this mean?

What are the Possible Causes of the DTC P18C5 Buick?

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

How to Fix the DTC P18C5 Buick?

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 P18C5 Buick 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.

Need more information about the P18C5 Buick code?

Need more information on how to fix the P18C5 Buick code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P18C5 Buick code diagnosed by a professional: Find a repair shop in your area

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 P18C5 Buick Code

1. What does the OBDII code P18C5 mean on a Buick?

P18C5 indicates a high voltage issue in the Gear Position Sensor Circuit 1, which monitors the transmission’s gear position for proper shifting and operation.

2. What are the symptoms of a P18C5 code in a Buick?

Common symptoms include erratic shifting, failure to shift gears, the transmission being stuck in one gear, or the illumination of the check engine light.

3. What causes the P18C5 code to appear in a Buick?

Possible causes include a faulty gear position sensor, damaged wiring or connectors in the circuit, a short to voltage, or an issue with the Transmission Control Module (TCM).

4. Can I drive my Buick with a P18C5 code?

It’s not recommended, as this code can affect transmission performance, potentially leading to unsafe driving conditions or further damage to the transmission system.

5. How is the P18C5 code diagnosed?

A mechanic will check for stored codes, inspect the gear position sensor and its circuit for damage, test the sensor’s voltage output, and verify the TCM’s functionality.

6. How can I fix the P18C5 code on my Buick?

Repairs may include replacing the gear position sensor, repairing or replacing damaged wiring or connectors, or updating/reprogramming the TCM if necessary.

7. How much does it cost to repair a P18C5 code on a Buick?

The cost varies depending on the specific issue, but replacing the gear position sensor typically costs $150-$300, including labor.

8. Can a faulty TCM cause a P18C5 code?

Yes, a malfunctioning Transmission Control Module can result in incorrect voltage readings that trigger the P18C5 code.

9. What tools do I need to troubleshoot a P18C5 code?

Tools include an OBDII scanner, a multimeter for voltage testing, and potentially a wiring diagram specific to your Buick model.

10. Will clearing the P18C5 code fix the problem?

Clearing the code without addressing the underlying issue will only temporarily erase it. The code will return if the problem persists.

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