AutoCodes – Generic – P157A

P157A Code - Sensor Supply Voltage Relay Feedback Circuit High Voltage

Quick Answer

The reductant control module relay 1 & 2 supply ignition voltage to the Reductant Control Module. Common causes include Faulty Reductant Control Module Relay 2, Reductant Control Module Relay 2 harness is open or shorted, Reductant Control Module Relay 2 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: P157A indicates Sensor Supply Voltage Relay Feedback Circuit High Voltage.
Common causes: Common causes include Faulty Reductant Control Module Relay 2, Reductant Control Module Relay 2 harness is open or shorted, Reductant Control Module Relay 2 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 3,298

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 25, 2021

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P157A Description

The reductant control module relay 1 & 2 supply ignition voltage to the Reductant Control Module. The Reductant Control Module Relay 2 also supplies ignition voltage to Nitrogen Oxide Sensor 1 & 2 and the Exhaust Particulate Matter Sensor. Both Reductant Control Module Relay 1 & 2 are controlled by a low side driver in the Engine Control Module (ECM).
The Diagnostic Trouble Code (DTC) will be set when the ECM detects the reductant control module relay 2 feedback circuit is shorted to voltage.

OBDII Code P157A - Sensor Supply Voltage Relay Feedback Circuit High Voltage - AutoCodes.com — P157A Code - Sensor Supply Voltage Relay Feedback Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P157A?

Faulty Reductant Control Module Relay 2
Reductant Control Module Relay 2 harness is open or shorted
Reductant Control Module Relay 2 circuit poor electrical connection

How to Fix the DTC P157A?

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 P157A 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 P157A code?

Need more information on how to fix the P157A code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P157A code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

P157A Buick — Sensor Supply Voltage Relay Feedback Circuit High Voltage
P157A Cadillac — Sensor Supply Voltage Relay Feedback Circuit High Voltage
P157A Chevrolet — Sensor Supply Voltage Relay Feedback Circuit High Voltage
P157A GMC — Sensor Supply Voltage Relay Feedback Circuit High Voltage

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 P157A Code

1. What are the common symptoms of OBDII code P157A?

- Common symptoms include poor engine performance, stalling, rough idling, and illuminated check engine light.

2. What can cause the Sensor Supply Voltage Relay Feedback Circuit High Voltage code (P157A) to trigger?

- This code can be triggered by issues such as a faulty sensor supply voltage relay, a short circuit in the wiring, or a malfunctioning sensor.

3. How serious is the P157A OBDII trouble code?

- While the severity can vary, it is important to address this code promptly to prevent potential engine damage and ensure optimal vehicle performance.

4. How can I diagnose the cause of the P157A trouble code?

- A thorough diagnostic process involving checking the sensor supply voltage relay, inspecting wiring for damage, and testing sensor functionality is recommended.

5. Can I continue driving with the P157A trouble code present?

- It is not recommended to continue driving with this code active as it can lead to further issues and potential damage to engine components.

6. What are some repair tips for addressing the P157A OBDII trouble code?

- Repair tips may include replacing the faulty sensor supply voltage relay, repairing any damaged wiring, and ensuring proper sensor function through testing.

7. How much does it typically cost to repair the P157A trouble code?

- The cost of repairs can vary depending on the underlying cause, but it is advisable to consult a professional mechanic for an accurate diagnosis and cost estimate.

8. Can a DIY enthusiast fix the P157A trouble code at home?

- While some may have the skills to address this code, it is recommended to seek assistance from a qualified mechanic to properly diagnose and repair the issue.

9. Will resetting the OBDII system clear the P157A trouble code?

- Resetting the system may temporarily clear the code, but if the underlying issue is not addressed, the code is likely to reappear.

10. How can I prevent the P157A trouble code from reoccurring in the future?

- Regular vehicle maintenance, prompt attention to check engine lights, and addressing any underlying issues promptly can help prevent the recurrence of this trouble code.