AutoCodes – Chevrolet – P18BB Chevrolet

P18BB Chevrolet Code - Internal Mode Switch 'B' Circuit Stuck Off 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: P18BB Chevrolet indicates Internal Mode Switch 'B' Circuit Stuck Off 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 1,417

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 P18BB Chevrolet 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 1.68 – 2.38 V for 2.7 s.

OBDII Code P18BB Chevrolet - Internal Mode Switch 'B' Circuit Stuck Off Invalid Voltage Range - AutoCodes.com — P18BB Chevrolet Code - Internal Mode Switch 'B' Circuit Stuck Off Invalid Voltage Range

What does this mean?

What are the Possible Causes of the DTC P18BB Chevrolet?

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 P18BB 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 P18BB 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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Information for Specific Chevrolet Models

P18BB 2014 Chevrolet Silverado — Internal Mode Switch 'B' Circuit Stuck Off Invalid Voltage Range
P18BB 2015 Chevrolet Silverado — Internal Mode Switch 'B' Circuit Stuck Off Invalid Voltage Range
P18BB 2016 Chevrolet Silverado — Internal Mode Switch 'B' Circuit Stuck Off Invalid Voltage Range
P18BB 2017 Chevrolet Silverado — Internal Mode Switch 'B' Circuit Stuck Off Invalid Voltage Range
P18BB 2018 Chevrolet Silverado — Internal Mode Switch 'B' Circuit Stuck Off 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 P18BB Chevrolet Code

What does the OBDII code P18BB mean for a Chevrolet vehicle?

The OBDII code P18BB indicates that the Internal Mode Switch 'B' Circuit is stuck off due to an invalid voltage range, which typically relates to issues in the transmission control system.

What are common symptoms of the P18BB code?

Common symptoms include transmission shifting problems, such as harsh or delayed shifts, the check engine light being illuminated, and potentially erratic behavior in the vehicle's performance.

What could cause the P18BB code to trigger?

The P18BB code can be triggered by a faulty Internal Mode Switch, damaged wiring or connectors in the circuit, or issues with the transmission control module itself.

How can I diagnose the P18BB code?

To diagnose the P18BB code, use an OBDII scanner to confirm the code, inspect the wiring and connectors for damage, test the Internal Mode Switch for proper operation, and check the transmission control module for faults.

What are some common repair tips for fixing the P18BB code?

Common repairs may include replacing a faulty Internal Mode Switch, repairing or replacing damaged wiring and connectors, and reprogramming or replacing the transmission control module if necessary.

Can I drive my Chevrolet with the P18BB code?

While it may be possible to drive the vehicle, it is not recommended due to potential transmission issues that could lead to further damage or unsafe driving conditions.

How much does it typically cost to repair the P18BB code?

Repair costs can vary widely depending on the specific issue, but you can expect to pay anywhere from $100 to $1,000 or more, especially if a new transmission control module is needed.

Is the P18BB code related to other OBDII codes?

Yes, the P18BB code may be related to other transmission-related codes, and itâ€™s advisable to check for additional codes to get a complete picture of the vehicle's diagnostic issues.

Can I clear the P18BB code without fixing the problem?

While you can clear the code using an OBDII scanner, it will likely reappear if the underlying issue is not resolved. Itâ€™s best to address the root cause to ensure proper vehicle operation.