AutoCodes – GMC – P18C0 GMC

P18C0 GMC Code - Internal Mode Switch 'B' 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: P18C0 GMC indicates Internal Mode Switch 'B' 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 1,363

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 P18C0 GMC 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 B signal circuit has an invalid voltage range of 0.70 – 0.96 V for 2.7 s.

OBDII Code P18C0 GMC - Internal Mode Switch 'B' Circuit Stuck On Invalid Voltage Range - AutoCodes.com — P18C0 GMC Code - Internal Mode Switch 'B' Circuit Stuck On Invalid Voltage Range

What does this mean?

What are the Possible Causes of the DTC P18C0 GMC?

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 P18C0 GMC?

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 P18C0 GMC 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 P18C0 GMC code?

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Information for Specific GMC Models

P18C0 2014 GMC Sierra — Internal Mode Switch 'B' Circuit Stuck On Invalid Voltage Range
P18C0 2015 GMC Sierra — Internal Mode Switch 'B' Circuit Stuck On Invalid Voltage Range
P18C0 2016 GMC Sierra — Internal Mode Switch 'B' Circuit Stuck On Invalid Voltage Range
P18C0 2017 GMC Sierra — Internal Mode Switch 'B' Circuit Stuck On Invalid Voltage Range
P18C0 2018 GMC Sierra — Internal Mode Switch 'B' Circuit Stuck On Invalid Voltage Range

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 P18C0 GMC Code

1. What are the common symptoms of OBDII code P18C0 for Internal Mode Switch 'B' Circuit Stuck On Invalid Voltage Range?

The common symptoms include issues with shifting gears, difficulty starting the vehicle, and the transmission staying in one gear.

2. What are the possible causes of OBDII code P18C0 for Internal Mode Switch 'B' Circuit Stuck On Invalid Voltage Range?

Possible causes include a faulty internal mode switch, damaged wiring or connectors, low transmission fluid levels, or a malfunctioning transmission control module.

3. How can I diagnose the Internal Mode Switch 'B' Circuit issue related to OBDII code P18C0?

Diagnosing this issue involves checking the internal mode switch for proper operation, inspecting the wiring and connectors for any damage, and testing the transmission control module for faults.

4. Can driving with OBDII code P18C0 cause further damage to the vehicle?

Continued driving with this code can potentially cause damage to the transmission system, leading to more serious and costly repairs in the future. It is recommended to address the issue promptly.

5. What are some repair tips for fixing OBDII code P18C0 related to Internal Mode Switch 'B' Circuit Stuck On Invalid Voltage Range?

Repair tips include checking and replacing the internal mode switch if necessary, repairing any damaged wiring or connectors, ensuring proper transmission fluid levels, and resetting the fault codes after repairs are completed.

6. Is it safe to continue driving with OBDII code P18C0 if the vehicle seems to be operating normally?

While the vehicle may seem to operate normally with this code, it is not recommended to continue driving without addressing the underlying issue. Ignoring the problem can lead to potential transmission issues in the future.

7. How much does it typically cost to repair OBDII code P18C0 for Internal Mode Switch 'B' Circuit Stuck On Invalid Voltage Range?

The cost of repair can vary depending on the extent of the issue and the specific repairs needed. It is advisable to consult a professional mechanic for an accurate diagnosis and cost estimate.

8. Can a DIY enthusiast fix OBDII code P18C0 related to Internal Mode Switch 'B' Circuit Stuck On Invalid Voltage Range?

While some DIY enthusiasts may be able to address this issue, it is recommended to have a professional mechanic diagnose and repair the problem to ensure proper resolution and prevent further damage.

9. How long does it typically take to repair OBDII code P18C0 for Internal Mode Switch 'B' Circuit Stuck On Invalid Voltage Range?

The repair time can vary depending on the complexity of the issue and the availability of parts. It is best to consult with a certified mechanic for an estimate of the repair duration.

10. Can resetting the OBDII code P18C0 resolve the issue temporarily?

Resetting the fault code may temporarily clear the warning light, but it will not fix the underlying problem causing the Internal Mode Switch 'B' Circuit Stuck On Invalid Voltage Range issue. It is important to diagnose and address the root cause of the code.