AutoCodes – Cadillac – B2478 Cadillac

B2478 Cadillac Code - Reverse Light Relay Shorted To Battery

Quick Answer

When Platform Zone Module (PZM) receives input that transaxle is in Reverse, PZM energizes reverse light relay which will turn on back-up lights. Common causes include Faulty Reverse Light Relay, Reverse Light Relay harness is open or shorted, Reverse Light Relay 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: B2478 Cadillac indicates Reverse Light Relay Shorted To Battery.
Common causes: Common causes include Faulty Reverse Light Relay, Reverse Light Relay harness is open or shorted, Reverse Light Relay 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 623

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

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Table of contents Created and updated by William Orellana on Dec 09, 2019

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code B2478 Cadillac Description

When Platform Zone Module (PZM) receives input that transaxle is in Reverse, PZM energizes reverse light relay which will turn on back-up lights. When back-up lights have been commanded on, PZM constantly measures voltage. The Diagnostic Trouble Code (DTC) B2478 will set when voltage is not at ground potential for at least 2 seconds. DTC B2478 will clear when voltage is greater than the ground for at least one monitoring cycle.

OBDII Code B2478 Cadillac - Reverse Light Relay Shorted To Battery - AutoCodes.com — B2478 Cadillac Code - Reverse Light Relay Shorted To Battery

What does this mean?

What are the Possible Causes of the DTC B2478 Cadillac?

Faulty Reverse Light Relay
Reverse Light Relay harness is open or shorted
Reverse Light Relay circuit poor electrical connection
Faulty Platform Zone Module (PZM)

How to Fix the DTC B2478 Cadillac?

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 B2478 Cadillac 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 B2478 Cadillac Code

1. What does the OBDII code B2478 mean on a Cadillac?

The code B2478 indicates that the reverse light relay circuit is shorted to the battery, causing improper functionality of the reverse lights.

2. What are the common symptoms of the B2478 code in a Cadillac?

Symptoms include reverse lights staying on constantly, not turning on at all, or erratic behavior when shifting into reverse.

3. What causes the B2478 code to appear in a Cadillac?

This code is typically caused by damaged wiring, a faulty reverse light relay, or a short circuit in the reverse light circuit.

4. Can the B2478 code affect vehicle performance?

No, it does not directly affect vehicle performance, but it may pose safety concerns, especially during nighttime driving or when reversing.

5. How do I diagnose the B2478 code in my Cadillac?

Start by inspecting the reverse light relay and its wiring for damage or corrosion. Use a multimeter to check for a short to the battery in the circuit.

6. Can I drive my Cadillac with the B2478 code?

Yes, but itâ€™s not recommended due to potential safety issues with the reverse lights not functioning properly.

7. How do you fix the B2478 code on a Cadillac?

Repairs may include replacing the reverse light relay, repairing or replacing damaged wiring, or fixing the short circuit causing the issue.

8. How much does it cost to repair the B2478 code in a Cadillac?

The cost can vary, but replacing a reverse light relay typically ranges from $50 to $150, depending on labor and parts.

9. Can a blown fuse cause the B2478 code on a Cadillac?

No, a blown fuse is not the cause of this code, but damaged wiring or a short to the battery could lead to related electrical issues.

10. How can I prevent the B2478 code from occurring in the future?

Regularly inspect the reverse light wiring and relay for wear, avoid driving in areas with excessive moisture, and ensure proper electrical connections.