P18BB 2015 GMC Sierra 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 2015 GMC Sierra 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.
Code P18BB 2015 GMC Sierra Description
What are the Possible Causes of the DTC P18BB 2015 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 P18BB 2015 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 P18BB 2015 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 P18BB 2015 GMC Sierra code?
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Frequently Asked Questions about P18BB 2015 GMC Sierra Code
1. What does the OBDII code P18BB mean on a 2015 GMC Sierra?
The P18BB code indicates that the Internal Mode Switch (IMS) 'B' circuit is stuck off due to an invalid voltage range detected by the transmission control module (TCM).
2. What are the common symptoms of the P18BB code?
Symptoms may include a check engine light, erratic shifting, inability to change gears, or the transmission being stuck in one gear.
3. What causes the P18BB code on a 2015 GMC Sierra?
Common causes include a faulty internal mode switch, damaged wiring or connectors in the IMS circuit, or a malfunctioning transmission control module.
4. Can driving with the P18BB code cause further damage?
Yes, driving with this code can lead to transmission issues, reduced performance, and potential long-term damage if not addressed promptly.
5. How is the P18BB code diagnosed?
A mechanic will use a scan tool to confirm the code, inspect the IMS circuit wiring and connectors, test the internal mode switch, and check for proper voltage signals.
6. What repairs are typically needed to fix the P18BB code?
Repairs may include replacing the internal mode switch, repairing or replacing damaged wiring or connectors, and in rare cases, reprogramming or replacing the TCM.
7. How much does it cost to fix the P18BB code?
Repair costs vary but may range from $200 to $600, depending on whether the issue is with the IMS, wiring, or TCM.
8. Can the P18BB code be fixed without professional help?
DIY repairs are possible if you are experienced with automotive electrical systems, but diagnosing and repairing transmission-related issues often requires specialized tools and knowledge.
9. Is the P18BB code a common issue for the 2015 GMC Sierra?
It isn’t the most common issue, but it can occur due to wear and tear, particularly in high-mileage vehicles.
10. Can the P18BB code reappear after repairs?
Yes, if the root cause isn’t fully addressed, such as failing to check all wiring or properly calibrate the TCM, the code may return.
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