AutoCodes – GMC – B0285 GMC

B0285 GMC Code - Electric Rear Defrost Circuit Low

Quick Answer

The Liftgate Module (LGM) monitors the voltage level on the supply voltage circuit of the rear window defogger. Common causes include Faulty Liftgate Module (LGM), Liftgate Module (LGM) harness is open or shorted, Liftgate Module (LGM) circuit poor electrical connection. Severity is Low - monitor the vehicle and repair when practical. The vehicle can usually be driven if no severe symptoms are present, but symptoms should be checked before extended driving.

What it means: B0285 GMC indicates Electric Rear Defrost Circuit Low.
Common causes: Common causes include Faulty Liftgate Module (LGM), Liftgate Module (LGM) harness is open or shorted, Liftgate Module (LGM) circuit poor electrical connection.
Severity: Low - monitor the vehicle and repair when practical.
Can I drive?: The vehicle can usually be driven if no severe symptoms are present, but symptoms should be checked before extended driving.

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Code Popularity 774

How popular is this code, among other codes? Low

Repair Importance Level

Low (Monitor) (1 / 3)

Repair Difficulty Level

Intermediate (2 / 3)

What is this?

Table of contents Created and updated by William Orellana on Mar 10, 2021

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code B0285 GMC Description

The Liftgate Module (LGM) monitors the voltage level on the supply voltage circuit of the rear window defogger. The LGM test the supply voltage circuit of the rear window defogger every 160 milliseconds. With the rear window defogger inactive, the supply voltage circuit of the rear window defogger will have no voltage present. With the rear window defogger active, the supply voltage circuit of the rear window defogger will be near system voltage.

OBDII Code B0285 GMC - Electric Rear Defrost Circuit Low - AutoCodes.com — B0285 GMC Code - Electric Rear Defrost Circuit Low

What does this mean?

What are the Possible Causes of the DTC B0285 GMC?

Faulty Liftgate Module (LGM)
Liftgate Module (LGM) harness is open or shorted
Liftgate Module (LGM) circuit poor electrical connection

How to Fix the DTC B0285 GMC?

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 B0285 GMC 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 B0285 GMC Code

1. What are the common symptoms of OBDII code B0285 GMC (Electric Rear Defrost Circuit Low)?

The common symptoms include a non-functioning rear defroster, decreased visibility through the rear window in cold or humid conditions, and a dashboard warning light indicating an issue with the rear defrost system.

2. What are the possible causes of OBDII code B0285 GMC?

Potential causes of this code include a faulty rear defrost relay, damaged rear defrost grid, wiring issues such as shorts or open circuits, or a malfunctioning rear defrost switch.

3. How can I diagnose the Electric Rear Defrost Circuit Low issue?

You can diagnose this issue by visually inspecting the rear defrost grid for damage, checking the rear defrost relay and switch for proper operation, and using a multimeter to test the continuity of the wiring in the defrost circuit.

4. Can I repair the Electric Rear Defrost Circuit Low issue myself?

Depending on your level of automotive expertise, you may be able to repair this issue yourself by replacing a faulty relay, repairing damaged wiring, or fixing a broken rear defrost grid. However, if you are unsure, it is recommended to seek professional help.

5. Is it safe to drive with OBDII code B0285 GMC active?

While it is generally safe to drive with this code active, it is important to address the issue promptly to ensure proper visibility through the rear window in adverse weather conditions.

6. How much does it typically cost to repair OBDII code B0285 GMC?

The cost of repairing this code can vary depending on the underlying cause of the issue. Simple fixes like replacing a relay or repairing wiring may be relatively inexpensive, while replacing a damaged rear defrost grid can be more costly.

7. Can a malfunctioning rear defrost system affect other vehicle systems?

While the rear defrost system is typically isolated from other vehicle systems, a malfunctioning rear defroster could potentially affect the vehicle's electrical system if left unresolved for an extended period of time.

8. Are there any preventive measures to avoid OBDII code B0285 GMC in the future?

To prevent this code from occurring, it is recommended to regularly inspect the rear defrost system for any signs of damage, ensure proper operation of the defrost switch and relay, and promptly address any issues that arise.

9. Will resetting the OBDII system clear the B0285 GMC code?

Resetting the OBDII system may temporarily clear the code, but if the underlying issue causing the Electric Rear Defrost Circuit Low problem is not addressed, the code is likely to reappear.

10. How long does it take to repair OBDII code B0285 GMC?

The repair time for this code can vary depending on the specific cause of the issue and the complexity of the repair needed. Simple fixes may take a short amount of time, while more involved repairs could require several hours or more.