Engine-Codes.com
Engine-Codes – Hyundai – P1635 Hyundai

P1635 Hyundai Code - Water Heater Relay Malfunction

Quick Answer

The P1635 diagnostic trouble code for Hyundai vehicles indicates a malfunction in the water heater relay. Common causes include Faulty water heater relay, Corrosion or damage to the relay wiring, Electrical issues in the vehicle's system. 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
P1635 Hyundai indicates Water Heater Relay Malfunction.
Common causes
Common causes include Faulty water heater relay, Corrosion or damage to the relay wiring, Electrical issues in the vehicle's system.
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 10, 2024
💬 Need more help? Ask Auto Expert for instant answers — it's free!
AutoCodes App

Fix Your Car Smarter

Try the New AutoCodes App!

Get complete OBDII diagnostics, repair solutions, and cost estimates, plus AI chat support on demand.

AutoCodes App on Google Play

Code P1635 Hyundai Description

The P1635 diagnostic trouble code for Hyundai vehicles indicates a malfunction in the water heater relay. In most Hyundai models, the water heater relay is responsible for controlling the flow of electricity to the engine's block heater, which helps warm up the engine in cold weather conditions. When this relay malfunctions, it can lead to issues with starting the vehicle in cold weather, reduced fuel efficiency, and potential damage to the engine due to increased wear and tear from cold starts.

OBDII Code P1635 Hyundai - Water Heater Relay Malfunction
P1635 Hyundai Code - Water Heater Relay Malfunction

Common Causes of P1635 Hyundai

  1. Faulty water heater relay
  2. Corrosion or damage to the relay wiring
  3. Electrical issues in the vehicle's system
  4. Poor connection or loose wiring in the relay circuit
  5. Extreme temperature fluctuations causing stress on the relay

Symptoms of P1635 Hyundai

  1. Difficulty starting the vehicle in cold weather
  2. Reduced fuel efficiency
  3. Engine running rough or stalling
  4. Check engine light illuminated on the dashboard
  5. Engine overheating in extreme cases

How to Fix P1635 Hyundai

  1. Begin by diagnosing the specific cause of the water heater relay malfunction using a diagnostic scan tool.
  2. Inspect the relay and its wiring for any signs of damage, corrosion, or loose connections.
  3. Replace the faulty water heater relay with a new one that meets the manufacturer's specifications.
  4. Test the new relay to ensure it is functioning correctly and that the issue has been resolved.
  5. Clear the diagnostic trouble code from the vehicle's computer system to reset the check engine light.

Cost to Fix P1635 Hyundai

The cost of repairing a water heater relay malfunction in a Hyundai vehicle can vary depending on the specific model, the extent of the damage, and labor rates in your area. On average, the parts for this repair can range from $50 to $150, while labor costs can range from $100 to $300. Overall, you can expect to pay between $150 and $450 for this repair at a professional auto repair shop. It is recommended to get quotes from multiple shops to ensure you are getting a fair price for the repair.

Need more information about the P1635 Hyundai code?

Need more information on how to fix the P1635 Hyundai code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P1635 Hyundai code diagnosed by a professional: Find a repair shop in your area

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 P1635 Hyundai Code

1. What does the OBDII code P1635 mean for Hyundai vehicles?

Code P1635 indicates a malfunction in the water heater relay, which is responsible for controlling the engine coolant heater system.

2. What are the common symptoms of the P1635 code?

Symptoms may include poor engine performance in cold weather, difficulty starting the engine, or the check engine light being illuminated.

3. What causes the P1635 code to appear on a Hyundai?

Common causes include a faulty water heater relay, damaged wiring or connectors, or issues with the engine control module (ECM).

4. How do I diagnose the P1635 code in my Hyundai?

Diagnose the code by inspecting the water heater relay, checking related wiring for damage, and using a multimeter to test for proper voltage and grounding.

5. Can I drive my Hyundai with the P1635 code active?

While the vehicle may still be drivable, ignoring the code could lead to reduced performance in cold weather and potential long-term damage to engine components.

6. How do I fix the P1635 code on a Hyundai?

Repairing the code typically involves replacing a faulty water heater relay, repairing damaged wiring, or reprogramming or replacing the ECM if necessary.

7. How much does it cost to repair the P1635 code?

Costs can vary but typically range from $50 to $150 for a relay replacement, with higher costs if ECM repairs or diagnostics are needed.

8. Will clearing the P1635 code fix the problem?

Clearing the code without addressing the underlying issue will only temporarily remove the warning; the problem will likely resurface.

9. How can I prevent the P1635 code from appearing again?

Regular maintenance, including inspecting the relay and wiring for wear, can help prevent this code from reoccurring.

10. Is the P1635 code specific to certain Hyundai models?

While it is most commonly found in Hyundai models with coolant heater systems, the exact implementation may vary by model and year.

Discuss the causes and fixes for P1635 Hyundai OBDII Code

Submit a New Comment

  • CODE P1635 WATER HEATER RELAY MALFUNCTION
    ANY INPUTS TO SOLVE THIS PROBLEM? HYUNDAI TUCSON 2007 DIESEL.
    THANKS...

    Reply to Comment

    • Thanks for your question. On a 2007 Hyundai Tucson diesel, the P1635 code points to a problem with the water heater relay circuit, which is part of the system that helps warm up the engine coolant faster during cold starts.

      Here’s what I’d suggest checking:

      • Water heater relay itself: It's usually located in the engine bay fuse/relay box. Check if it's stuck, burned, or clicking when the engine starts cold.
      • Power and ground at the relay: Use a multimeter to make sure the relay is getting proper voltage and ground. A faulty fuse or corroded connection could cause the issue.
      • Coolant heater element: If the heater element itself is shorted or has high resistance, it can trigger the code. Disconnect it and check resistance with a meter.
      • Wiring harness: Look for damage or corrosion on the wires going to the heater and relay, especially near connectors.

      This system only activates under certain conditions (usually cold ambient temp and engine temp), so if you’re testing it, try when the engine is cold.

      Reply to Comment