AutoCodes – GMC – P157A GMC

P157A GMC 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 GMC 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 1,710

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

What does this mean?

What are the Possible Causes of the DTC P157A GMC?

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 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 P157A 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 P157A GMC Code

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

The common symptoms of OBDII code P157A GMC include rough engine idle, stalling, poor acceleration, and illuminated check engine light.

2. What could cause the Sensor Supply Voltage Relay Feedback Circuit High Voltage code (P157A GMC)?

The P157A GMC code can be triggered by issues such as a faulty sensor supply voltage relay, damaged wiring or connectors, or a malfunctioning sensor itself.

3. How can I diagnose the cause of OBDII code P157A GMC?

To diagnose the cause of code P157A GMC, you can perform a visual inspection of the sensor and its wiring, check the sensor supply voltage relay, and use a diagnostic scanner to gather more data on the issue.

4. What are the potential repair options for OBDII code P157A GMC?

Potential repair options for code P157A GMC include replacing the faulty sensor supply voltage relay, repairing damaged wiring or connectors, or replacing the sensor if it is found to be malfunctioning.

5. Can I drive my vehicle with OBDII code P157A GMC active?

It is not recommended to drive your vehicle with an active P157A GMC code, as it can lead to poor engine performance and potential further damage if left unresolved.

6. How urgent is it to address OBDII code P157A GMC?

While the severity of the issue may vary, it is generally recommended to address code P157A GMC promptly to prevent any potential damage to the engine or related components.

7. Can a DIY enthusiast fix OBDII code P157A GMC at home?

Depending on your skill level and access to tools, you may be able to address code P157A GMC at home by following repair guides or seeking assistance from online forums.

8. How much does it typically cost to repair OBDII code P157A GMC at a mechanic?

The cost of repairing OBDII code P157A GMC at a mechanic can vary depending on the specific cause of the issue, but it may range from a few hundred to over a thousand dollars.

9. Are there any preventative measures to avoid OBDII code P157A GMC in the future?

To prevent OBDII code P157A GMC in the future, it is important to regularly inspect and maintain the electrical components of your vehicle, such as sensors and wiring.

10. Can OBDII code P157A GMC be related to other engine issues?

While code P157A GMC specifically relates to the sensor supply voltage relay feedback circuit, it is possible for this issue to be connected to other engine-related problems, so a thorough diagnosis is recommended.