AutoCodes – Buick – P18C2 Buick

P18C2 Buick Code - Internal Mode Switch 'P' Circuit Stuck On Invalid Voltage Range

Quick Answer

The internal mode switch indicates the Transmission Control Module (TCM) which gear position the vehicle operator has selected. Common causes include Faulty Transmission Internal Mode Switch, Transmission Internal Mode Switch harness is open or shorted, Transmission Internal Mode Switch 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: P18C2 Buick indicates Internal Mode Switch 'P' Circuit Stuck On Invalid Voltage Range.
Common causes: Common causes include Faulty Transmission Internal Mode Switch, Transmission Internal Mode Switch harness is open or shorted, Transmission Internal Mode Switch 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 920

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 Mar 23, 2024

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P18C2 Buick Description

The internal mode switch indicates the Transmission Control Module (TCM) which gear position the vehicle operator has selected. The internal mode switch consists of 5 separate hall effect switches. Each hall effect switch is supplied with a 9 V reference circuit and a signal circuit from the TCM. Each signal circuit for each gear selector position will have either a voltage reading of 0.70-0.96 V indicating On or 1.68-2.38 V indicating Off. The voltage values on each internal mode switch circuit will change and are dependent on the position of the gear selector. The state of each internal mode switch A/B/C/P/S signal circuit is displayed on the scan tool. The Diagnostic Trouble Code (DTC) will be set when the TCM has detected the internal mode switch P signal circuit has an invalid voltage range of 0.70 – 0.96 V for 2.7 s.

OBDII Code P18C2 Buick - Internal Mode Switch 'P' Circuit Stuck On Invalid Voltage Range - AutoCodes.com — P18C2 Buick Code - Internal Mode Switch 'P' Circuit Stuck On Invalid Voltage Range

What does this mean?

What are the Possible Causes of the DTC P18C2 Buick?

Faulty Transmission Internal Mode Switch
Transmission Internal Mode Switch harness is open or shorted
Transmission Internal Mode Switch circuit poor electrical connection
Faulty Transmission Control Module (TCM)

How to Fix the DTC P18C2 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 P18C2 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.

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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 P18C2 Buick Code

1. What are the common symptoms of OBDII code P18C2 in a Buick related to the Internal Mode Switch 'P' Circuit Stuck On Invalid Voltage Range?

Symptoms may include issues with gear shifting, transmission performance, and the inability to engage certain gears.

2. What are the possible causes of OBDII code P18C2 in a Buick?

Common causes may include a faulty internal mode switch, damaged wiring or connectors, low transmission fluid levels, or internal transmission issues.

3. How can I diagnose OBDII code P18C2 in my Buick?

Diagnosis typically involves using a scan tool to retrieve the fault code, testing the internal mode switch and related components for proper voltage and continuity, and checking for any visible signs of damage or corrosion.

4. Can driving with OBDII code P18C2 in a Buick cause further damage?

Continuing to drive with this code may lead to further transmission issues or potential safety hazards due to improper gear engagement.

5. How can I repair OBDII code P18C2 in my Buick?

Repair options may include replacing the internal mode switch, repairing or replacing damaged wiring or connectors, ensuring proper transmission fluid levels, or seeking professional assistance for more complex transmission repairs.

6. Is it safe to continue driving my Buick with OBDII code P18C2 if the symptoms are not severe?

It is not recommended to drive the vehicle with unresolved OBDII codes, as they can indicate underlying issues that may worsen over time and lead to more extensive repairs.

7. Can I reset OBDII code P18C2 in my Buick using a simple OBDII scanner?

While you can clear the code with a scanner, it is important to address the root cause of the issue to prevent the code from reoccurring.

8. How much does it typically cost to repair OBDII code P18C2 in a Buick at a dealership or repair shop?

Costs can vary depending on the specific repairs needed, but it is advisable to obtain a diagnostic and repair estimate from a trusted mechanic or dealership.

9. Are there any preventive maintenance tips to avoid OBDII code P18C2 in a Buick in the future?

Regularly checking and maintaining the transmission system, including fluid levels and condition, can help prevent issues like the Internal Mode Switch 'P' Circuit Stuck On Invalid Voltage Range.

10. Can a DIY enthusiast with basic automotive knowledge repair OBDII code P18C2 in a Buick?

Depending on the specific issue causing the code, some repairs may be within reach for DIY enthusiasts. However, more complex transmission-related problems may require professional expertise.