What is the code C1391 on a Toyota Highlander?
The Toyota Highlander is a popular mid-size SUV known for its reliability and performance. However, like any vehicle, it can sometimes encounter error codes that indicate a problem with the vehicle's systems. One such code is C1391, which can be a cause for concern for Highlander owners. In this article, we'll explore what the C1391 code means and how it can be addressed.
What is the C1391 Code?
The C1391 code is a diagnostic trouble code (DTC) that is specific to the Toyota Highlander. This code indicates a problem with the vehicle's engine control module (ECM) or the engine's electronic throttle control system. The C1391 code is typically triggered when the ECM detects an issue with the throttle position sensor or the throttle actuator control circuit.
Causes of the C1391 Code
There are several potential causes for the C1391 code in a Toyota Highlander:
- Faulty throttle position sensor: The throttle position sensor is responsible for monitoring the position of the throttle and relaying that information to the ECM. If the sensor is malfunctioning, it can trigger the C1391 code.
- Wiring issues: Problems with the wiring harness or connectors between the throttle position sensor and the ECM can also cause the C1391 code to be set.
- Throttle actuator control circuit issues: The throttle actuator control circuit is responsible for controlling the opening and closing of the throttle. If there is a problem with this circuit, it can trigger the C1391 code.
- ECM issues: In some cases, the C1391 code can be caused by a problem with the ECM itself, such as a software or hardware failure.
It's important to note that the C1391 code can also be triggered by other issues, such as a problem with the engine's air intake system or the fuel system. A thorough diagnosis by a qualified mechanic is necessary to determine the root cause of the problem.
Symptoms of the C1391 Code
When the C1391 code is set, the Highlander may exhibit one or more of the following symptoms:
- Rough idling: The engine may run rough or uneven when idling.
- Hesitation or stalling: The vehicle may hesitate or stall when accelerating or under load.
- Reduced engine power: The Highlander may experience a noticeable loss of power or performance.
- Illuminated check engine light: The check engine light on the dashboard will be illuminated, indicating a problem with the vehicle's systems.
If you notice any of these symptoms in your Toyota Highlander, it's important to have the vehicle diagnosed and the C1391 code addressed as soon as possible to prevent further damage or safety issues.
Addressing the C1391 Code
To address the C1391 code in a Toyota Highlander, the following steps may be taken:
- Diagnostic testing: A qualified mechanic will use a diagnostic tool to scan the vehicle's computer system and retrieve the specific code, as well as any additional diagnostic information that can help identify the root cause of the problem.
- Inspection and testing of components: The mechanic will visually inspect the throttle position sensor, wiring harness, and throttle actuator control circuit for any signs of damage or wear. They may also perform additional testing, such as voltage checks or sensor calibration, to pinpoint the issue.
- Replacement of faulty components: If a faulty component is identified, such as a malfunctioning throttle position sensor, the mechanic will replace the component to resolve the issue.
- ECM reprogramming or replacement: In some cases, the C1391 code may be caused by a problem with the ECM itself. If this is the case, the ECM may need to be reprogrammed or replaced to resolve the issue.
Once the necessary repairs or replacements have been made, the mechanic will clear the C1391 code and test the vehicle to ensure the problem has been resolved.
How do you fix the code C1391?
Fixing the C1391 Error Code
To resolve this issue, we replace the faulty brake master cylinder and brake booster accumulator with original Toyota parts. After installation, we perform a full system calibration to ensure proper brake operation and restore the vehicle's safety features.
What is the code C1391 on a 2013 Prius?
The 2013 Prius code C1391 indicates an abnormal leak in the brake actuator, specifically the accumulator pressure, which can cause spongy brakes and trigger warning lights. Common causes include failing seals in the brake booster or accumulator, or vacuum leaks in the associated lines and pump. It is recommended to first inspect for external leaks, vacuum line damage, and ensure the brake fluid is clean before considering a replacement of the brake booster and accumulator assembly.
Causes of C1391
- Internal leak in the brake booster/accumulator: The most common cause is a failure of internal seals, leading to pressure loss.
- Vacuum leaks: Cracks in the vacuum lines or a faulty check valve can cause pressure to drop.
- Faulty vacuum pump: The vacuum pump may not be able to build adequate pressure if it is malfunctioning.
- Contaminated brake fluid: Air in the brake fluid system can be a symptom or cause of the pressure loss.
Symptoms
- Brake warning lights: ABS, traction control, and brake system warning lights will likely illuminate.
- Spongy or soft brake pedal: The pedal may feel less responsive or require more pressure.
- Continuous buzzing or hissing sound: The brake booster pump may run constantly as it tries to compensate for the pressure loss.
- Fluctuating brake performance: Braking may feel inconsistent.
How to troubleshoot and fix
- 1. Check for a recall or warranty extension: Toyota has issued coverage for this issue on many 2010-2015 Prius models. Check with a dealer to see if your vehicle is eligible for a free or covered repair.
- 2. Inspect for external issues:
- Look for any external leaks in the brake lines.
- Inspect all vacuum lines connected to the booster for cracks, damage, or disconnections.
- Confirm the brake fluid reservoir is full and the fluid is clean.
- 3. Test the system:
- A professional can use a scan tool to monitor the pressure sensor and test the operation of the booster pump.
- 4. Address the leak:
- Replace any damaged vacuum lines or faulty components.
- If the issue persists, the brake booster and accumulator assembly likely needs to be replaced.
- 5. Flush the system: After any repairs, thoroughly flush the brake fluid to remove any air that may have entered the system.
What is the recall on the Toyota C1391?
Toyota is providing coverage for repairs related to the certain internal malfunctions of the brake booster assemblies. One or more of the following specific Diagnostic Trouble Codes (DTCs) C1391, C1252, C1256 or C1253 will be stored in the vehicles memory to be used as verification.
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What is the abnormal leak of ACC press C1391?
The C1391 code indicates an abnormal leak in the brake accumulator pressure, meaning the ABS system cannot build sufficient pressure for proper power braking. This is often caused by worn seals or hoses within the brake actuator assembly, a failing brake booster, or other internal leaks. This can lead to a loss of power brakes and potentially trigger warning lights, and it's recommended to stop driving and have the system inspected, as a component replacement is often required.
Causes of the C1391 code
- Internal leaks in the brake actuator: Degraded internal seals in the brake booster/accumulator assembly are a common cause.
- Leaking brake lines or hoses: Cracks or wear in the rubber hoses or brake lines can cause pressure loss.
- Faulty components: The code can also be triggered by a failing vacuum pump, malfunctioning check valves, or other issues within the brake system.
What to do
- Stop driving immediately: Do not continue to drive the vehicle, as it is unsafe with a failing brake system.
- Check for recalls: Before making repairs, check with Toyota to see if there are any recalls or extended warranty coverage for your vehicle's brake system.
- Inspect the system: A professional should inspect the entire brake actuator assembly, including the master cylinder, accumulator, and lines, for any signs of leaks or damage.
- Be prepared for replacement: Repairs typically involve replacing the entire brake actuator assembly, which can be a complex and expensive job.
- Use a professional scan tool: A professional may need to use a specific diagnostic tool, like a Toyota Techstream, to clear the codes after the repair is completed.
