What is OBD-II Code P21C3 – Reductant Heater Relay Control Circuit Low
As a mechanic, one of the most common issues I come across in vehicles is OBD-II codes. These codes provide valuable information about the vehicle’s health and can help diagnose issues in a timely manner. In this article, I will be explaining OBD-II code P21C3 – Reductant Heater Relay Control Circuit Low. I will provide a detailed explanation of what this code means, what causes it, and how to repair it. This article is aimed at helping the average person who may not have a lot of technical knowledge about cars understand this issue and potentially repair it themselves.
What is OBD-II Code P21C3?
OBD-II code P21C3 refers to a low circuit in the reductant heater relay control circuit. The reductant heater is responsible for heating up diesel exhaust fluid so that it can be used to reduce harmful emissions. When this code appears, it means that there is an issue within the relay that controls the heater, which results in the heater not functioning correctly.
What Causes OBD-II Code P21C3?
There can be a few different causes of OBD-II code P21C3. The most common cause is a faulty relay control module. Over time, these modules can wear down and stop functioning correctly, leading to this code. Another cause can be a faulty heater element, which can prevent the heating process from starting or cause it to shut off prematurely.
Another potential cause is a wiring issue. If any of the wiring that connects to the reductant heater relay circuit becomes damaged or corroded, it can prevent the system from receiving the electrical signals it needs to function correctly. Finally, a damaged sensor or control unit can also be a cause of this code.
How to Repair OBD-II Code P21C3?
The first step in repairing OBD-II code P21C3 is to identify the underlying cause of the issue. Typically, this will require diagnostic testing equipment to be connected to the vehicle. The technician will then run a series of tests to identify where the issue is occurring.
Once the underlying cause has been identified, the actual repair process can begin. If the issue is a faulty relay control module, the module will need to be replaced with a new one. This is a relatively straightforward repair that can often be completed in a single visit to the mechanic.
If the issue is a faulty heater element, this will also need to be replaced. In some cases, this can be done without replacing the entire reductant heater assembly. However, in other cases, it may be necessary to replace the entire assembly to ensure that the issue is fully resolved.
If the issue is a wiring or sensor issue, the relevant components will need to be inspected and replaced as necessary. This can be a more complex repair process and may require more time and expertise to complete.
Frequently Asked Questions
Q1. What is a reductant heater relay control circuit?
A: The reductant heater relay control circuit is a system within a vehicle that is responsible for heating up diesel exhaust fluid so that it can be used to reduce harmful emissions.
Q2. What are the symptoms of OBD-II code P21C3?
A: The primary symptom of OBD-II code P21C3 is a lack of heat from the reductant heater. This can lead to increased exhaust emissions and reduced vehicle performance.
Q3. Is it safe to drive with OBD-II code P21C3?
A: It is generally not recommended to drive with OBD-II code P21C3 as it can negatively impact the vehicle’s performance and potentially cause damage to other components.
Q4. Can I repair OBD-II code P21C3 myself?
A: While it is possible to repair OBD-II code P21C3 yourself, it is generally recommended to seek the assistance of a professional mechanic.
Q5. How can I prevent OBD-II code P21C3 from occurring in the future?
A: The best way to prevent OBD-II code P21C3 from occurring is to ensure that the vehicle is properly maintained and serviced on a regular schedule. This includes regular inspections of the reductant heater and associated components.
20% off Additional Services at Valvoline Instant Oil Change
20% off Cabin Air Filter Replacement at Valvoline Instant Oil Change
