U1821 Code - Lost Communication With 14V Power Module On Powertrain Expansion Communication Bus
Quick Answer
Devices connected to the powertrain high-speed General Motor Local Area Network (GMLAN) serial data circuits monitor for serial data communications during normal vehicle operation. Common causes include Faulty 14V Power Module, 14V Power Module harness is open or shorted, 14V Power Module 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
- U1821 indicates Lost Communication With 14V Power Module On Powertrain Expansion Communication Bus.
- Common causes
- Common causes include Faulty 14V Power Module, 14V Power Module harness is open or shorted, 14V Power Module 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.
Code U1821 Description
The Diagnostic Trouble Code (DTC) will set when a supervised periodic message that includes the transmitter device availability has not been received.
What are the Possible Causes of the DTC U1821?
- Faulty 14V Power Module
- 14V Power Module harness is open or shorted
- 14V Power Module circuit poor electrical connection
How to Fix the DTC U1821?
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 U1821 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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Get the U1821 code diagnosed by a professional: Find a repair shop in your area
Information for Specific Makes
- U1821 Buick — Lost Communication With 14V Power Module On Powertrain Expansion Communication Bus
- U1821 Cadillac — Lost Communication With 14V Power Module On Powertrain Expansion Communication Bus
- U1821 Chevrolet — Lost Communication With 14V Power Module On Powertrain Expansion Communication Bus
- U1821 GMC — Lost Communication With 14V Power Module On Powertrain Expansion Communication Bus
Frequently Asked Questions about U1821 Code
1. What are the common symptoms of OBDII code U1821?
- Common symptoms include erratic engine performance, difficulty starting the vehicle, and illuminated warning lights on the dashboard.
2. What are the potential causes of OBDII code U1821?
- The code U1821 can be caused by issues such as a faulty 14V power module, damaged wiring or connectors in the powertrain expansion communication bus, or a communication breakdown between modules.
3. How can I diagnose OBDII code U1821?
- Diagnosing code U1821 typically involves using a professional OBDII scanner to retrieve the fault codes and then performing a thorough inspection of the powertrain expansion communication bus components and connections.
4. What are some common repair tips for addressing code U1821?
- Check the power module and related components for any visible damage or signs of wear. Inspect the wiring harness and connectors for corrosion or loose connections. Resetting the fault codes and testing the system after repairs can help in resolving the issue.
5. Can I drive my vehicle with OBDII code U1821?
- It is not recommended to drive the vehicle with code U1821 present, as it can lead to potential safety hazards and further damage to the vehicle's systems. It is best to address the issue promptly.
6. How serious is OBDII code U1821?
- While code U1821 may not always cause immediate drivability issues, it is a serious fault that can affect the overall performance and safety of the vehicle. Ignoring the code can lead to more severe problems over time.
7. Is it safe to attempt repairs for code U1821 at home?
- Depending on your level of automotive knowledge and experience, you may be able to perform basic inspections and repairs related to code U1821 at home. However, for more complex issues, it is advisable to seek professional help.
8. How much does it typically cost to repair OBDII code U1821?
- The cost of repairing code U1821 can vary depending on the extent of the issue, the required parts, and labor costs. It is recommended to obtain quotes from automotive professionals for an accurate estimate.
9. Can a weak battery cause OBDII code U1821 to appear?
- Yes, a weak or failing battery can sometimes trigger code U1821 due to insufficient power supply to the modules. It is advisable to ensure the battery is in good condition and fully charged before diagnosing the code further.
10. Are there any recalls related to OBDII code U1821?
- It is recommended to check with the vehicle manufacturer or authorized service centers for any recalls or technical service bulletins related to OBDII code U1821, as they may provide additional information or assistance in resolving the issue.
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