AutoCodes – Cadillac – P248B Cadillac

P248B Cadillac Code - Reductant Heater 1 Feedback Circuit High Voltage

Quick Answer

As reductant will freeze at temperatures below -11°C (12°F), there are 2 reductant heaters located in the reductant tank. Common causes include Faulty Reductant Line Heater, Reductant Line Heater harness is open or shorted, Reductant Line Heater 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: P248B Cadillac indicates Reductant Heater 1 Feedback Circuit High Voltage.
Common causes: Common causes include Faulty Reductant Line Heater, Reductant Line Heater harness is open or shorted, Reductant Line Heater 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 294

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 Jul 29, 2021

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P248B Cadillac Description

As reductant will freeze at temperatures below -11°C (12°F), there are 2 reductant heaters located in the reductant tank. One heats the reductant in the tank, and one heats the reductant supplied to the reductant injector supply pipe. The Engine Control Module (ECM) monitors the reductant temperature in the tank in order to determine if the reductant temperature is below its freeze point. If the ECM determines that the reductant may be frozen, it activates a defrost strategy energizing the reductant heater. This energizing action terminates when the temperature sensor measures a threshold value over which the heater must be deactivated. The Diagnostic Trouble Code (DTC) will be set when there is greater than a 3 V difference between battery voltage and reductant tank heater voltage.

OBDII Code P248B Cadillac - Reductant Heater 1 Feedback Circuit High Voltage - AutoCodes.com — P248B Cadillac Code - Reductant Heater 1 Feedback Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P248B Cadillac?

Faulty Reductant Line Heater
Reductant Line Heater harness is open or shorted
Reductant Line Heater circuit poor electrical connection
Faulty Reductant Pump and Sensor Assembly
Faulty Reductant Control Module

How to Fix the DTC P248B 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 P248B 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 P248B Cadillac Code

1. What does the OBDII code P248B mean for a Cadillac?

P248B indicates a problem with the reductant heater 1 feedback circuit, specifically a high voltage issue detected by the vehicle's powertrain control module (PCM).

2. What are the common symptoms of code P248B on a Cadillac?

Symptoms may include the check engine light turning on, poor DEF (Diesel Exhaust Fluid) system performance, reduced engine power, and possible failure to meet emissions standards.

3. What causes the P248B code on a Cadillac?

Common causes include a faulty reductant heater, damaged wiring or connectors in the heater circuit, a malfunctioning PCM, or corrosion in the reductant system's electrical components.

4. Can I drive my Cadillac with the P248B code?

While you may still be able to drive, prolonged operation with this code can lead to decreased emissions performance and may eventually trigger limp mode, limiting engine power.

5. How do I diagnose the P248B code on my Cadillac?

Start by inspecting the reductant heater and its wiring for damage or corrosion. Use a multimeter to check for proper voltage in the circuit and scan the system for additional related codes.

6. How can I fix the P248B code on a Cadillac?

Repairs may involve replacing the faulty reductant heater, repairing damaged wiring or connectors, cleaning corroded connections, or, in rare cases, reprogramming or replacing the PCM.

7. How much does it cost to repair the P248B code on a Cadillac?

Repair costs vary depending on the issue, but replacing the reductant heater typically ranges from $200 to $600, including parts and labor.

8. What is the purpose of the reductant heater in a Cadillac?

The reductant heater warms the Diesel Exhaust Fluid (DEF) to ensure proper flow and injection into the exhaust system, especially in cold weather.

9. Can a faulty reductant heater trigger other OBDII codes?

Yes, a defective reductant heater can trigger related codes, such as P20BA or P20B9, which also indicate issues within the DEF heater system.

10. How can I prevent the P248B code from reoccurring on my Cadillac?

Regularly inspect and maintain the DEF system, especially the heater and associated wiring, to prevent corrosion or damage from causing electrical issues.