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Engine-Codes – GMC – P20C5 GMC

P20C5 GMC Code - Reductant Heater 'D' Control Circuit/Open

Quick Answer

The P20C5 GMC code indicates a problem with the Reductant Heater 'D' control circuit, specifically that it is open or not functioning properly. Common causes include Faulty reductant heater 'D', Wiring issues in the control circuit, Corrosion or damage to electrical connections. 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
P20C5 GMC indicates Reductant Heater 'D' Control Circuit/Open.
Common causes
Common causes include Faulty reductant heater 'D', Wiring issues in the control circuit, Corrosion or damage to electrical connections.
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.
What is this?
Table of contents Created and updated by William Orellana on Sep 09, 2024
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Code P20C5 GMC Description

The P20C5 GMC code indicates a problem with the Reductant Heater 'D' control circuit, specifically that it is open or not functioning properly. The reductant heater is a component of the selective catalytic reduction (SCR) system, which is responsible for reducing nitrogen oxide emissions in diesel vehicles. The reductant heater warms up the diesel exhaust fluid (DEF) before it enters the SCR catalyst, ensuring optimal performance of the emission control system.

OBDII Code P20C5 GMC - Reductant Heater 'D' Control Circuit/Open
P20C5 GMC Code - Reductant Heater 'D' Control Circuit/Open

Common Causes of P20C5 GMC

  1. Faulty reductant heater 'D'
  2. Wiring issues in the control circuit
  3. Corrosion or damage to electrical connections
  4. ECM software issues
  5. Defective temperature sensors

Symptoms of P20C5 GMC

  1. Check engine light illuminated
  2. Reduced fuel efficiency
  3. Decreased performance
  4. Failed emissions test
  5. Diesel exhaust fluid (DEF) freezing in cold weather

How to Fix P20C5 GMC

  1. Diagnose the specific cause of the issue by using a diagnostic scanner to read the code and test the reductant heater 'D'.
  2. Inspect the wiring and connections for any damage or corrosion. Repair or replace as needed.
  3. Test the temperature sensors to ensure they are functioning correctly. Replace if necessary.
  4. Clear the code from the ECM and reset the system.
  5. Test drive the vehicle to ensure the issue has been resolved and the code does not reappear.

Cost to Fix P20C5 GMC

The cost of repairing a P20C5 GMC code can vary depending on the cause of the issue and the specific parts that need to be replaced. On average, the repair cost can range from $200 to $500, including parts and labor. It's important to note that diagnostic time and labor rates at auto repair shops can vary, so it's recommended to get quotes from multiple shops to find the best price.

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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 P20C5 GMC Code

1. What does the OBDII code P20C5 mean for a GMC vehicle?

P20C5 indicates a problem in the Reductant Heater 'D' control circuit, such as an open circuit or failure in the wiring or heater itself.

2. What are the symptoms of the P20C5 code in a GMC?

Common symptoms include an illuminated check engine light, poor DEF (Diesel Exhaust Fluid) system performance, and potentially reduced engine power.

3. What causes the P20C5 code to appear on a GMC vehicle?

Causes can include a faulty reductant heater, damaged wiring or connectors, a blown fuse, or a malfunctioning control module.

4. Can I drive my GMC with a P20C5 code?

Driving with this code is possible short-term, but it may lead to DEF system issues, reduced fuel efficiency, or reduced engine power if not addressed.

5. How do I diagnose the P20C5 code on my GMC?

Diagnosis involves checking the heater's resistance, inspecting wiring and connectors for damage, and testing the control circuit for proper voltage.

6. How much does it cost to fix a P20C5 code on a GMC?

Repair costs vary, but replacing a reductant heater can cost between $200 and $600, depending on parts and labor.

7. Can a blown fuse cause the P20C5 code on a GMC?

Yes, a blown fuse in the reductant heater circuit can trigger this code and should be checked during diagnostics.

8. How do I reset the P20C5 code after repairs on my GMC?

After repairs, use an OBDII scan tool to clear the code and verify that it does not return after a test drive.

9. Does the P20C5 code affect emissions on a GMC?

Yes, this code can impact emissions as it relates to the DEF system, which reduces NOx emissions in diesel engines.

10. Is the P20C5 code common in GMC diesel vehicles?

Yes, this code is relatively common in GMC diesel vehicles with DEF systems, especially in colder climates where the reductant heater is more active.

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