AutoCodes – Buick – B318A Buick

B318A Buick Code - Left Rear Window Switch

Quick Answer

The driver and passenger window motors supply 12 V signal circuits to their respective window switches, when a window switch has been activated, a switch closes providing a ground to the appropriate signal circuit causing the voltage to drop to 0 V. Common causes include Faulty Left Rear Window Switch, Left Rear Window Switch harness is open or shorted, Left Rear Window 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: B318A Buick indicates Left Rear Window Switch.
Common causes: Common causes include Faulty Left Rear Window Switch, Left Rear Window Switch harness is open or shorted, Left Rear Window 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 522

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 Jun 11, 2023

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code B318A Buick Description

The driver and passenger window motors supply 12 V signal circuits to their respective window switches, when a window switch has been activated, a switch closes providing a ground to the appropriate signal circuit causing the voltage to drop to 0 V. The window motor will detect the voltage drop in the signal circuit and will command the window to move in the desired direction.
The driver window master control switch also contains control switches for the passenger, left rear and right rear window functions. When a window switch is pressed, a serial data message is sent to the Body Control Module (BCM). The BCM examines the request and checks for messages from other power window motors that may prohibit window movement. If no prohibitive messages have been received, the BCM will send a serial data message to the passenger window motor or to the appropriate rear window switch which will perform the command as requested.

OBDII Code B318A Buick - Left Rear Window Switch - AutoCodes.com — B318A Buick Code - Left Rear Window Switch

What does this mean?

What are the Possible Causes of the DTC B318A Buick?

Faulty Left Rear Window Switch
Left Rear Window Switch harness is open or shorted
Left Rear Window Switch circuit poor electrical connection
Faulty Body Control Module (BCM)

How to Fix the DTC B318A Buick?

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 B318A Buick 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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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 B318A Buick Code

1. What does the OBDII code B318A mean for a Buick?

The B318A code indicates a fault related to the left rear window switch, usually involving communication or electrical issues.

2. What are common symptoms of the B318A code in a Buick?

Symptoms include the left rear window not responding to switch commands, intermittent operation, or complete failure to move.

3. What causes the B318A code to trigger?

Common causes include a faulty left rear window switch, damaged wiring, a blown fuse, or issues with the Body Control Module (BCM).

4. Can a bad window motor cause the B318A code?

While the code specifically points to the switch, a faulty window motor could indirectly contribute if it causes excessive electrical resistance.

5. How can I diagnose the B318A code on a Buick?

Start by inspecting the window switch, fuses, and wiring for damage or wear. A scan tool can confirm if the switch is not sending proper signals to the BCM.

6. Is it safe to drive with the B318A code active?

Yes, the code doesnâ€™t affect drivability, but the left rear window may not function properly.

7. How do I fix the B318A code on my Buick?

Repair or replace the left rear window switch if faulty, check and repair any damaged wiring, and clear the code with a scan tool once the issue is fixed.

8. Can the B318A code reset on its own?

The code may reset temporarily if the issue is intermittent, but it will likely return until the underlying problem is resolved.

9. How much does it cost to repair the B318A code?

The repair cost depends on the specific issue but typically ranges from $50 to $150 for a new switch, excluding labor.

10. Can I replace the left rear window switch myself to fix the B318A code?

Yes, with basic tools and automotive knowledge, you can replace the switch yourself. However, ensure you disconnect the battery before working on electrical components.