P1603 Throttle Control Unit Detected Loss of Return Spring

How to Diagnose and Solve P1603 Throttle Control Unit Detected Loss of Return Spring Issues

As a car enthusiast, there’s nothing more satisfying than rolling up your sleeves and getting down to some good old DIY car maintenance. Today, we’re going to tackle a common issue that many car owners face – the P1603 Throttle Control Unit Detected Loss of Return Spring issue.

Understanding the P1603 Code

Before we dive into the nitty-gritty of diagnosing and solving this problem, let’s first understand what the P1603 code means. This code is triggered when the Engine Control Unit (ECU) detects a malfunction in the throttle control return spring. This spring is crucial as it helps control the throttle’s opening and closing, ensuring your car runs smoothly.

Signs of a P1603 Code

How do you know if your car is suffering from this issue? Here are some common signs:

1. **Check Engine Light**: This is usually the first sign. If your check engine light is on, it’s time to investigate.
2. **Poor Acceleration**: If your car isn’t accelerating as it should, it could be due to a faulty throttle control return spring.
3. **Unstable Idling**: If your car’s idle is unstable or erratic, this could be another sign of the P1603 code.

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Diagnosing the P1603 Code

Now that we know what to look out for, let’s move on to diagnosing the issue.

Step 1: Use an OBD-II Scanner

The first step in diagnosing this issue is to use an OBD-II scanner. This device can read the trouble codes stored in your car’s ECU. If the P1603 code is present, it will show up on the scanner.

Step 2: Inspect the Throttle Control Unit

Next, visually inspect the throttle control unit. Look for any signs of damage or wear and tear. If the return spring is visibly damaged or missing, you’ve found your problem.

Solving the P1603 Code

Once you’ve diagnosed the issue, it’s time to solve it.

Step 1: Replace the Throttle Control Return Spring

If the return spring is damaged or missing, it will need to be replaced. This is a relatively simple process that can be done with basic tools.

Step 2: Reset the ECU

After replacing the spring, you’ll need to reset the ECU to clear the P1603 code. This can be done using the OBD-II scanner.

Step 3: Test Drive

Finally, take your car for a test drive to ensure the issue has been resolved. If the check engine light stays off and your car is running smoothly, you’ve successfully solved the P1603 code!


Fixing a P1603 Throttle Control Unit Detected Loss of Return Spring issue may seem daunting, but with a little patience and the right tools, it’s a task you can tackle at home. Remember, regular maintenance and inspections can help prevent such issues from arising in the first place.


1. Can I drive my car with a P1603 code?

While it’s possible to drive with a P1603 code, it’s not recommended. The faulty return spring could cause poor acceleration and unstable idling, which could lead to a dangerous situation on the road.

2. How much does it cost to fix a P1603 code?

The cost to fix a P1603 code can vary depending on the make and model of your car. However, if you choose to do it yourself, you’ll only need to pay for the replacement spring and possibly an OBD-II scanner.

3. Can a P1603 code cause other issues in my car?

Yes, a P1603 code can cause other issues if left untreated. It can lead to poor fuel efficiency, increased emissions, and potential damage to other components of your car’s engine.