P18B5 2018 GMC Sierra Code - Internal Mode Switch 'A' Circuit Shorted
Quick Answer
The P18B5 diagnostic trouble code (DTC) for the 2018 GMC Sierra indicates that there is a short circuit in the internal mode switch 'A' circuit. Common causes include Damaged wiring or connectors in the IMS 'A' circuit, Faulty internal mode switch, Malfunctioning transmission control module. 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
- P18B5 2018 GMC Sierra indicates Internal Mode Switch 'A' Circuit Shorted.
- Common causes
- Common causes include Damaged wiring or connectors in the IMS 'A' circuit, Faulty internal mode switch, Malfunctioning transmission control module.
- 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.
Fix Your Car Smarter
Try the New AutoCodes App!
Get complete OBDII diagnostics, repair solutions, and cost estimates, plus AI chat support on demand.
Code P18B5 2018 GMC Sierra Description
The P18B5 diagnostic trouble code (DTC) for the 2018 GMC Sierra indicates that there is a short circuit in the internal mode switch 'A' circuit. The internal mode switch (IMS) is an essential component of the transmission system that helps control the shift points and mode selection of the transmission. When the IMS 'A' circuit is shorted, it can disrupt the communication between the transmission control module (TCM) and the IMS, leading to erratic shifting patterns, incorrect gear selection, and potential safety hazards.
Common Causes of P18B5 2018 GMC Sierra
- Damaged wiring or connectors in the IMS 'A' circuit
- Faulty internal mode switch
- Malfunctioning transmission control module
- Electrical issues within the transmission system
- Corrosion or moisture intrusion in the transmission components
Symptoms of P18B5 2018 GMC Sierra
- Erratic shifting patterns
- Delayed or harsh gear shifts
- Stalling or hesitation during acceleration
- Reduced fuel efficiency
- Illumination of the Check Engine Light
How to Fix P18B5 2018 GMC Sierra
- Perform a thorough diagnostic scan to confirm the P18B5 code and identify the specific cause of the short circuit.
- Inspect the wiring harness and connectors in the IMS 'A' circuit for any signs of damage, corrosion, or loose connections.
- Test the internal mode switch functionality and replace it if found faulty.
- Check the transmission control module for proper operation and replace if necessary.
- Clear the DTC and perform a test drive to ensure the issue has been resolved.
Cost to Fix P18B5 2018 GMC Sierra
The cost of repairing the P18B5 code for the internal mode switch 'A' circuit shorted in a 2018 GMC Sierra can vary depending on the specific cause of the issue and the labor rates at the auto repair shop. Generally, the cost of parts for this repair can range from $100 to $300, while the labor cost can be between $150 and $300. Therefore, the total repair cost can be estimated to be between $250 and $600. It is advisable to consult with a professional mechanic for a more accurate estimate based on the vehicle's condition and location.
Need more information about the P18B5 2018 GMC Sierra code?
Need more information on how to fix the P18B5 2018 GMC Sierra code? Get Access to Factory Service Manuals
Need Help with the Code?
Get the P18B5 2018 GMC Sierra code diagnosed by a professional: Find a repair shop in your area
Frequently Asked Questions about P18B5 2018 GMC Sierra Code
1. What does the OBDII code P18B5 mean on a 2018 GMC Sierra?
The P18B5 code indicates an issue with the Internal Mode Switch (IMS) 'A' Circuit, specifically a short in the circuit.
2. What are the common symptoms of P18B5 in a 2018 GMC Sierra?
Symptoms may include the transmission stuck in one gear, harsh shifting, erratic gear changes, or the check engine light turning on.
3. What causes the P18B5 code to appear?
Common causes include a shorted IMS wiring harness, a faulty IMS, corroded or loose connections, or a malfunction in the transmission control module (TCM).
4. How do I diagnose the P18B5 code in my 2018 GMC Sierra?
Diagnosis typically involves inspecting the IMS wiring for damage, checking for loose or corroded connectors, testing the IMS itself, and scanning the TCM for additional codes.
5. Can I drive my 2018 GMC Sierra with the P18B5 code?
While the truck may still be drivable, continued use could cause further damage to the transmission. It’s best to address the issue as soon as possible.
6. How do I fix the P18B5 code on a GMC Sierra?
Repairs may involve replacing damaged wiring, cleaning or securing connections, replacing the faulty IMS, or reprogramming/repairing the TCM.
7. What is the Internal Mode Switch (IMS) in a 2018 GMC Sierra?
The IMS is a component in the transmission that helps the vehicle’s computer determine the selected gear and mode of operation.
8. How much does it cost to repair a P18B5 code?
The cost depends on the root cause, but replacing the IMS typically costs $200–$500, including parts and labor. Wiring or TCM issues may vary.
9. Can a bad battery cause the P18B5 code?
While unlikely, low voltage from a failing battery can sometimes cause electrical issues that might trigger this or related codes.
10. Do I need to reset the code after fixing the P18B5 issue?
Yes, after completing repairs, clear the code with an OBDII scanner and test drive the vehicle to ensure the issue is resolved.
Discuss the causes and fixes for P18B5 2018 GMC Sierra OBDII Code
Code P18B5 2018 GMC Sierra comments
No comments found for this page.
Fix Your Car Smarter
Try the New AutoCodes App!
Get complete OBDII diagnostics, repair solutions, and cost estimates, plus AI chat support on demand.