AutoCodes – Generic – B2123

B2123 Code - Ignition Run Control Circuit High

Quick Answer

The Front Control Module monitors the Ignition Run Control Circuit. Common causes include Faulty Run Relay, Run Relay harness is open or shorted, Run 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: B2123 indicates Ignition Run Control Circuit High.
Common causes: Common causes include Faulty Run Relay, Run Relay harness is open or shorted, Run 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.

Save to My Repairs My Repairs

AI answers can be wrong. Verify repairs with testing. Open full chat

Code Popularity 7,724

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 Sep 17, 2019

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
Add Comment

💬 Need more help? Ask Coddy for instant answers — it's free!

Code B2123 Description

The Front Control Module monitors the Ignition Run Control Circuit. The Front Control Module will set this Diagnostic Trouble Code (DTC) within 500ms if the Run Relay Control Circuit voltage is shorted to voltage.

OBDII Code B2123 - Ignition Run Control Circuit High - AutoCodes.com — B2123 Code - Ignition Run Control Circuit High

What does this mean?

What are the Possible Causes of the DTC B2123?

Faulty Run Relay
Run Relay harness is open or shorted
Run Relay circuit poor electrical connection
Faulty Front Control Module (FCM)

How to Fix the DTC B2123?

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 B2123 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.

Need more information about the B2123 code?

Need more information on how to fix the B2123 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the B2123 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

B2123 Chrysler — Ignition Run Control Circuit High
B2123 Dodge — Ignition Run Control Circuit High
B2123 Jeep — Ignition Run Control Circuit High
B2123 RAM — Ignition Run Control Circuit High

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 B2123 Code

What does OBDII code B2123 mean?

OBDII code B2123 indicates a problem with the Ignition Run Control Circuit, specifically that the circuit voltage is higher than expected.

What are common symptoms of the B2123 code?

Common symptoms include difficulty starting the vehicle, intermittent electrical issues, or warning lights on the dashboard, particularly related to the ignition system.

What could cause the B2123 code to trigger?

Possible causes include a short circuit in the ignition run control circuit, a faulty ignition switch, damaged wiring or connectors, or issues with the powertrain control module (PCM).

How can I diagnose the B2123 code?

To diagnose the B2123 code, check the ignition switch for proper operation, inspect wiring and connectors for damage, and use a multimeter to test circuit voltage levels.

What are some common repair steps for a B2123 code?

Repairs may involve repairing or replacing damaged wiring, replacing the ignition switch, or addressing issues within the PCM as necessary.

Can the B2123 code cause drivability issues?

Yes, the B2123 code can lead to drivability issues such as stalling, poor engine performance, or starting problems due to the ignition system malfunction.

Is it safe to drive with the B2123 code?

While it may be possible to drive the vehicle, it is not recommended as it can lead to further electrical issues or an inability to start the vehicle.

How can I clear the B2123 code after repairs?

After making repairs, you can clear the B2123 code using an OBDII scanner by selecting the "Erase Codes" option or by disconnecting the vehicle's battery for a short period.

Should I consult a professional mechanic for the B2123 code?

If you are unable to diagnose or repair the issue yourself, it is advisable to consult a professional mechanic to ensure proper handling and resolution of the problem.