P157A Chevrolet Code - Sensor Supply Voltage Relay Feedback Circuit High Voltage
Quick Answer
The P157A Chevrolet code indicates an issue with the sensor supply voltage relay feedback circuit having a high voltage. Common causes include Faulty Sensor Relay: A defective sensor relay can cause high voltage supply to the sensor, triggering this code, Wiring Issues: Damaged or corroded wiring connecting the sensor relay can disrupt the voltage supply, Malfunctioning Sensor: A faulty sensor itself can lead to incorrect voltage readings and trigger the code. 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 Chevrolet indicates Sensor Supply Voltage Relay Feedback Circuit High Voltage.
- Common causes
- Common causes include Faulty Sensor Relay: A defective sensor relay can cause high voltage supply to the sensor, triggering this code, Wiring Issues: Damaged or corroded wiring connecting the sensor relay can disrupt the voltage supply, Malfunctioning Sensor: A faulty sensor itself can lead to incorrect voltage readings and trigger the code.
- 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 P157A Chevrolet Description
The P157A Chevrolet code indicates an issue with the sensor supply voltage relay feedback circuit having a high voltage. In simpler terms, it means that there is a problem with the voltage supply to a sensor relay in the vehicle, which is causing the voltage to be higher than the specified range. This can have various implications on the vehicle's performance and systems.
Common Causes of P157A Chevrolet
- Faulty Sensor Relay: A defective sensor relay can cause high voltage supply to the sensor, triggering this code.
- Wiring Issues: Damaged or corroded wiring connecting the sensor relay can disrupt the voltage supply.
- Malfunctioning Sensor: A faulty sensor itself can lead to incorrect voltage readings and trigger the code.
- Electrical System Problems: Issues with the vehicle's electrical system, such as a faulty fuse or relay, can cause high voltage supply to the sensor.
Symptoms of P157A Chevrolet
- Check Engine Light: The most common symptom associated with this code is the illumination of the check engine light on the dashboard.
- Poor Engine Performance: The vehicle may experience rough idling, hesitation, or a lack of power when accelerating.
- Decreased Fuel Efficiency: A high voltage supply to the sensor relay can lead to incorrect fuel mixture, resulting in decreased fuel efficiency.
- Stalling: In severe cases, the vehicle may stall while driving or have difficulty starting.
- Erratic Sensor Readings: The vehicle's computer system may receive erratic or incorrect sensor readings, affecting overall performance.
How to Fix P157A Chevrolet
- Diagnose the Issue: Use a diagnostic scanner to retrieve the specific code and pinpoint the exact sensor and circuit affected.
- Inspect Wiring: Check the wiring connecting the sensor relay for any damage, corrosion, or loose connections.
- Test Sensor Relay: Test the sensor relay to determine if it is functioning correctly or needs to be replaced.
- Replace Sensor: If the sensor is found to be faulty, replace it with a new unit to ensure accurate readings.
- Clear Codes: After completing the repair, clear the diagnostic trouble codes and perform a test drive to verify the issue has been resolved.
Cost to Fix P157A Chevrolet
The typical repair costs for addressing a P157A Chevrolet code can vary depending on the specific cause of the issue and the parts needed for repair. On average, the cost for parts and labor to diagnose and fix this problem can range from $150 to $400. It is important to note that labor rates at auto repair shops can vary based on location, vehicle make and model, and engine type. It is recommended to consult with a local auto repair shop for a more accurate estimate based on your specific situation.
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Frequently Asked Questions about P157A Chevrolet Code
1. What are the common symptoms of OBDII code P157A in a Chevrolet related to the Sensor Supply Voltage Relay Feedback Circuit High Voltage?
- Common symptoms include illuminated check engine light, reduced engine performance, and potential stalling or rough idling.
2. What are some possible causes of the Sensor Supply Voltage Relay Feedback Circuit High Voltage code P157A in a Chevrolet?
- Potential causes include a faulty sensor supply voltage relay, wiring issues, a damaged sensor, or a problem with the powertrain control module (PCM).
3. How can I diagnose the OBDII code P157A in my Chevrolet related to the Sensor Supply Voltage Relay Feedback Circuit High Voltage?
- Diagnose by using an OBDII scanner to retrieve the code, inspecting the wiring and connections related to the sensor supply voltage relay, and testing the voltage output of the relay.
4. Can I drive my Chevrolet with the P157A code triggered?
- It is not recommended to drive your vehicle with the P157A code triggered as it can lead to further damage and potential safety risks. It's best to address the issue promptly.
5. How can I repair the Sensor Supply Voltage Relay Feedback Circuit High Voltage issue in my Chevrolet?
- Repair steps may include replacing the faulty sensor supply voltage relay, repairing any damaged wiring, and clearing the code with an OBDII scanner after the repairs are completed.
6. Is it possible for a DIY enthusiast to fix the P157A code in a Chevrolet?
- While some aspects of diagnosing and repairing the issue may be within reach for DIY enthusiasts, dealing with electrical components and sensor circuits may require professional expertise to ensure proper diagnosis and repair.
7. Will resetting the OBDII code P157A in my Chevrolet make the issue go away permanently?
- Simply resetting the code without addressing the underlying cause will not fix the problem permanently. It's important to diagnose the issue properly and carry out the necessary repairs.
8. How long does it typically take to repair the Sensor Supply Voltage Relay Feedback Circuit High Voltage issue in a Chevrolet?
- The repair time can vary based on the exact cause of the issue, but it may take anywhere from a few hours to a full day, depending on the complexity of the repair.
9. Are there any preventive measures to avoid triggering the P157A code in a Chevrolet?
- Regular vehicle maintenance, including checking the sensor circuits and wiring, can help prevent issues that may trigger the P157A code related to the Sensor Supply Voltage Relay Feedback Circuit High Voltage.
10. Can the P157A code in a Chevrolet be related to other underlying issues in the vehicle?
- While the P157A code specifically points to an issue with the Sensor Supply Voltage Relay Feedback Circuit High Voltage, it's always recommended to conduct a thorough diagnosis to rule out any other potential related problems in the vehicle.
Discuss the causes and fixes for P157A Chevrolet OBDII Code
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P157a code
I read where relay 1&2 conrol the voltage to the def module,but where are these 2 relays located. 1&2 on my fuse panel are fuses not relays.
2018 chevy 2500 duramax 6.6-
The P157A code on your 2018 Chevy 2500 Duramax means the ECM saw too much voltage on the sensor supply voltage relay feedback circuit. Specifically, it's tied to the Reductant Control Module Relay 1 and 2, which supply ignition voltage to the reductant control module—and relay 2 also powers the NOₓ and DPF sensors.
Those relays aren’t labeled “Relay 1” and “Relay 2” in your fuse panel—they’re part of the Reductant Control Module assembly, typically near the engine bay or firewall alongside the emissions control components. You'll see them clustered with the DPF/NOₓ equipment.
78 -- DEF HEATER -- KR121A Reductant Control Module Relay 1
79 -- PT SENSOR -- KR121B Reductant Control Module Relay 2
Here’s what to check:
- Visually inspect the relay module and sockets for corrosion, damage, or melted pins.
- Consider swapping or testing the relay 2 (the one feeding NOₓ sensors) if you can identify it—you’re looking for an internal short causing high voltage.
- Check wiring harnesses and connectors going to that relay assembly—look for chafed insulation or pin corrosion.
- If relays and wiring look good, the reductant control module itself may be at fault.
Pulling the relay module off the engine bay and bench-testing or swapping relays is often enough to track down the issue.
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On the 2019 Silverado, there isn’t a single “sensor supply relay” sitting by itself like on older trucks.
That relay is built into the underhood fuse block (engine bay fuse box) and works as part of the power distribution system that feeds the ECM and sensors.
So when you’re looking for it, you won’t find a separate plug-in relay labeled exactly for that code. It’s part of the fuse/relay assembly on the driver side of the engine compartment.
For a P157A, the issue is usually not the relay itself but one of these:
• Low or unstable battery voltage
• Poor ground connection
• Loose or corroded terminals at the fuse block
• Wiring issue between the fuse block and ECM
• Internal fault in the fuse block (less common)What I would check first:
• Battery condition and voltage under load
• Main grounds (engine and frame)
• Remove the fuse box cover and inspect for heat damage or loose terminals
• Check related fuses for proper fit and no corrosionIf everything checks out and the code keeps coming back, sometimes the underhood fuse block itself ends up being the problem, but that’s after ruling out power and wiring issues.
So short answer: it’s in the underhood fuse block, not a separate relay you can just swap out.
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On most newer Chevrolets, there isn’t a separate “sensor relay” you can unplug and swap like older vehicles.
The sensor supply relay is built into the underhood fuse block and works as part of the power distribution to the ECM and sensors. So you won’t find a standalone relay labeled for it.
For a P157A, the issue is usually not the relay itself but something affecting that circuit, like:
• Low or unstable battery voltage
• Poor ground connection
• Loose or corroded terminals at the fuse box
• Wiring issue between the fuse block and ECM
• Internal fault in the fuse block (less common)So if you’re trying to locate it, look at the fuse/relay box in the engine bay, not for a separate relay.
Start by checking battery voltage, grounds, and the fuse block connections — that’s where most of these problems end up being.
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