P18B9 2016 GMC Sierra Code - Internal Mode Switch 'S' Circuit Shorted
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
- P18B9 2016 GMC Sierra indicates Internal Mode Switch 'S' Circuit Shorted.
- 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.
Code P18B9 2016 GMC Sierra Description
What are the Possible Causes of the DTC P18B9 2016 GMC Sierra?
- 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 P18B9 2016 GMC Sierra?
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 P18B9 2016 GMC Sierra 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 P18B9 2016 GMC Sierra code?
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Frequently Asked Questions about P18B9 2016 GMC Sierra Code
1. What does the OBDII code P18B9 mean on a 2016 GMC Sierra?
The P18B9 code indicates that the Internal Mode Switch "S" circuit has a short, which is part of the transmission range sensor or related circuitry.
2. What are the symptoms of code P18B9 in a GMC Sierra?
Common symptoms include the check engine light turning on, erratic or incorrect gear shifting, transmission stuck in one gear, or the inability to start the vehicle.
3. What causes the P18B9 code to appear?
Causes can include a short circuit in the wiring, a faulty transmission range sensor, water intrusion, corroded connectors, or a damaged shift lever assembly.
4. How is the P18B9 code diagnosed?
A mechanic will use a scan tool to confirm the code, inspect the wiring and connectors for damage or corrosion, and test the transmission range sensor for proper operation.
5. Can I drive my 2016 GMC Sierra with the P18B9 code active?
Driving with this code is not recommended as it may cause further damage to the transmission or lead to unsafe driving conditions due to gear selection issues.
6. How do I repair the P18B9 code on a GMC Sierra?
Repairs may include replacing damaged wiring, cleaning or reconnecting corroded connectors, or replacing the transmission range sensor or shift lever assembly.
7. How much does it cost to fix the P18B9 code on a 2016 GMC Sierra?
Repair costs vary but typically range from $100 to $500, depending on whether it's a simple wiring issue or the transmission range sensor needs replacement.
8. What tools are needed to fix the P18B9 code?
Common tools include a scan tool for diagnostics, a multimeter for testing circuits, and basic hand tools to access and replace components.
9. Can a P18B9 code be caused by low transmission fluid?
No, this specific code is related to an electrical issue in the Internal Mode Switch circuit and not directly linked to transmission fluid levels.
10. Will clearing the P18B9 code with a scan tool fix the problem?
Clearing the code may temporarily turn off the check engine light, but the underlying issue must be repaired to prevent the code from returning.
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