AutoCodes – GMC – B0978 GMC

B0978 GMC Code - Accessory Indicator Control Circuit

Quick Answer

The Ignition Mode Switch has 3 LEDs that indicate the vehicle power mode. Common causes include Faulty Ignition Mode Switch, Ignition Mode Switch harness is open or shorted, Ignition 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: B0978 GMC indicates Accessory Indicator Control Circuit.
Common causes: Common causes include Faulty Ignition Mode Switch, Ignition Mode Switch harness is open or shorted, Ignition 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.

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Code Popularity 884

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 Mar 11, 2021

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code B0978 GMC Description

The Ignition Mode Switch has 3 LEDs that indicate the vehicle power mode. When the vehicle is in the Off mode, the Off LED may illuminate. Pressing the lower button of the ignition mode switch, the vehicle enters the accessory mode and ACC LED will illuminate. Keeping the lower button pressed for about 5-6 seconds, the vehicle enters run mode with the engine off and the START LED will illuminate. All these LEDs have the voltage supplied from the Body Control Module (BCM) through the ignition mode switch supply voltage circuit. The ground path for each LED is controlled by the BCM.

OBDII Code B0978 GMC - Accessory Indicator Control Circuit - AutoCodes.com — B0978 GMC Code - Accessory Indicator Control Circuit

What does this mean?

What are the Possible Causes of the DTC B0978 GMC?

Faulty Ignition Mode Switch
Ignition Mode Switch harness is open or shorted
Ignition Mode Switch circuit poor electrical connection
Faulty Body Control Module (BCM)

How to Fix the DTC B0978 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 B0978 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 B0978 GMC Code

1. What are the common symptoms of OBDII code B0978 GMC (Accessory Indicator Control Circuit)?

- Common symptoms include the accessory indicator light not functioning properly, flickering, or staying on when it should be off.

2. What are the possible causes of OBDII code B0978 GMC?

- The code B0978 GMC can be caused by a faulty accessory indicator control circuit, a loose or corroded connector, or a malfunctioning accessory indicator switch.

3. How can I diagnose the OBDII code B0978 GMC?

- To diagnose the code B0978 GMC, a thorough inspection of the accessory indicator control circuit, connectors, and switch is necessary. Using a multimeter to test for continuity and voltage can help pinpoint the issue.

4. Can a DIYer repair OBDII code B0978 GMC?

- Repairing OBDII code B0978 GMC may require advanced electrical troubleshooting skills. DIYers with experience in automotive electrical systems may be able to diagnose and repair the issue, but it's recommended to seek professional help if unsure.

5. Is it safe to continue driving with OBDII code B0978 GMC?

- While the code B0978 GMC may not directly affect the drivability of the vehicle, it's important to address the underlying issue promptly to prevent potential electrical problems or safety hazards.

6. How much does it typically cost to repair OBDII code B0978 GMC?

- The cost of repairing OBDII code B0978 GMC can vary depending on the underlying cause and labor rates in your area. However, it's advisable to budget for diagnostic fees, replacement parts, and labor costs.

7. Can a faulty accessory indicator control circuit cause other issues in the vehicle?

- A faulty accessory indicator control circuit may not directly cause other issues, but it can indicate potential electrical problems in the vehicle that may need attention to prevent further complications.

8. Are there any preventive measures to avoid OBDII code B0978 GMC?

- Regularly inspecting and maintaining the electrical components related to the accessory indicator system can help prevent issues that may trigger OBDII code B0978 GMC.

9. Can weather conditions affect the occurrence of OBDII code B0978 GMC?

- Extreme weather conditions or water exposure can potentially damage the accessory indicator control circuit or connectors, leading to the triggering of OBDII code B0978 GMC.

10. How long does it typically take to repair OBDII code B0978 GMC?

- The repair time for OBDII code B0978 GMC can vary depending on the exact cause of the issue and the complexity of the repair. In some cases, it may be resolved quickly, while other scenarios may require more extensive troubleshooting and repair work.