P1605 Toyota Code: Engine Rough Idling Solutions - OBD ADVISOR (2024)

Welcome to our informative guide on P1605 Toyota, a diagnostic trouble code that can affect the performance and reliability of your Toyota vehicle.

If you’ve encountered this code, it’s important not to panic. In this article, we’ll explore P1605 Toyota in-depth, covering its meaning, severity, symptoms, causes, diagnosis, and repair steps.

As a seasoned mechanic with years of experience, I aim to share my expertise and help you navigate through this issue effectively.

So, let’s dive in and solve the P1605 Toyota together.

P1605 Toyota: A Quick Overview

Here’s a quick overview of the P1605 for Toyota. Check it out!

• Definition: Engine Rough Idling
• Severity: Medium
• DIY Skill Level: Advanced
• Continue To Drive?: No
• Estimated Repair Cost: $200 – $500

Understanding The Meaning Of P1605 Toyota – Engine Rough Idling

The P1605 diagnostic trouble code is triggered when the engine speed of a Toyota vehicle drops below the set speed. Specifically, this code is stored when, after 5 seconds or more elapse following engine startup, the engine speed decreases to 400 rpm or less, as detected by the vehicle’s onboard computer (ECM) using a one-trip detection logic.

To fully comprehend the implications of P1605 Toyota, it’s essential to understand the systems and components involved. This code is typically associated with the engine control and SFI (Sequential Fuel Injection) systems. These systems work together to regulate the engine’s performance, fuel injection timing, and various other parameters to ensure smooth operation.

When the engine speed drops below the set speed, it indicates an irregularity in the engine’s idle control or a potential malfunction within the components linked to idle stability.

Commonly affected models include the Corolla (especially years 2012 and 2015), Highlander, Tundra, Camry (especially years 2012, 2013, and 2014), RAV4, Tacoma, Vitz, Hilux, Land Cruiser, Prado, 4Runner, Belta, Yaris, and Land Cruiser.

It’s worth noting that the P1605 code is often associated with related codes, such as P1603 and P1604, which further aid in diagnosing the underlying issue.

Read more: Complete Toyota OBD1/OBD2 Codes List [FREE DOWNLOAD]

Special Note About P1605 Toyota Code

In some specific Toyota models, the P1605 code can refer to a Knock Control CPU malfunction, indicating a problem with the engine’s knock control system. However, it’s important to note that this article specifically focuses on the P1605 code pertaining to Engine Rough Idling. The information provided here is intended for diagnosing and resolving engine rough idling issues associated with the P1605 code.

If your Toyota model is affected by the Knock Control CPU malfunction, it is recommended to consult a professional mechanic or authorized Toyota service center for an accurate diagnosis and appropriate resolution, which may involve checking the Engine Control Module (ECM) for faults or malfunctions and repairing or replacing it if necessary.

How Serious Is The P1605 Toyota Code?

When it comes to the severity of the P1605 Toyota code, it is generally considered to have a moderate level of severity. While it may not pose an immediate safety risk, it is crucial not to ignore or neglect this code.

Driving with the P1605 code present can lead to various issues, including rough idling, decreased engine performance, and potential stalling. These symptoms can impact the overall drivability and reliability of your Toyota vehicle.

To ensure the longevity and optimal performance of your vehicle, it is advisable to address the P1605 code promptly. Continuing to drive without addressing the underlying cause can potentially lead to further damage to engine components or other related systems.

Read more: Toyota Dashboard Symbols and Meanings (FULL list, Free Download)

Common Symptoms Of P1605 Toyota

The P1605 Toyota code can manifest in various symptoms, indicating an issue with the engine speed or idle control. Common symptoms include:

• Check engine light illuminated
• Rough idle
• Slow acceleration
• Engine vibration leading to engine shutdown
• Engine shutdown without vibration
• Engine starts with accelerator pedal depressed
• Rough idling after engine startup

Exploring The Causes Of P1605 Toyota

The P1605 Toyota code can have various underlying causes that trigger the engine speed drop. To help you easily follow the list, the causes are categorized as follows:

How To Accurately Diagnose And Repair P1605 Toyota Code?

In this section, we will cover the essential tools and parts required, provide a step-by-step procedure for diagnosing and fixing the code, and discuss the DIY repair level and estimated costs.

Diagnostic Tools And Essential Parts

To diagnose and repair the P1605 Toyota code, you may need the following tools and parts:

• Diagnostic scanner
• Multimeter
• Vacuum gauge
• Smoke machine
• Intake gaskets
• Sensor replacement parts
• Ignition components
• Fuel system components

Step-by-Step Guide

Diagnosing and fixing the P1605 Toyota code involves two cases based on the engine speed decrease. Follow the steps below for each case:

Case 1: Engine Speed Decreased Slowly

Step 1: Inspect ignition system

Inspect the ignition system components, including spark plugs, power supply circuit, and ignition coil assembly. Look for any faults or malfunctions. Repair or replace if required.

Step 2: Perform air fuel ratio check

• Inspect the intake system for air leaks. Check the connections and brake booster assembly. Repair any leaks found.
• Test the air-fuel ratio related sensors, such as the mass air flow meter, air-fuel ratio sensor, thermostat sensor, and engine coolant temperature sensor. Repair or replace any malfunctioning sensors indicating richness or leanness beyond normal limits.
• Verify the fuel supply system, including the fuel pump control circuit, purge VSV system, fuel lines, and ECM. Repair or replace any damaged components.

If the vehicle still exhibits abnormal behavior, proceed to the next steps.

Step 3: Check intake air volume

• Check the intake air volume to ensure it is sufficient. Inspect the air passage for obstructions and excessive valve overlap in the camshaft timing oil control valve assembly. Repair or replace faulty components if necessary.
• Clean the intake manifold and throttle body if required.
• Check the vacuum system for leaks and repair any detected issues.

Step 4: Verify ignition timing

Verify that the ignition timing is operating properly. Adjust it if necessary to ensure correct timing.

Case 2: Engine Speed Decreased Rapidly

Step 1: Check electrical system

• Inspect the ignition and injection system for any electrical system malfunctions.
• Look for signs of power interruption or temporary power cuts.
• Examine the power supply circuit to the fuel injector and ignition coil assemblies.
• Repair or replace any faulty components in the electrical system.

Step 2: Verify external load

• Examine external components that may be causing an increased load on the engine, such as the power steering or air conditioning system.
• Note any malfunctions or abnormalities in these external parts.

Step 3: Address external part malfunctions

If any external part malfunctions are identified, repair or replace the faulty components. Ensure proper functioning of external systems that can impact engine load.

DIY Repair Level And Estimated Costs

The repair procedure for the P1605 Toyota code is classified as advanced. It involves checking and inspecting multiple components within the engine system, requiring a good understanding of engine systems, diagnostic tools, and troubleshooting techniques.

If you are unsure or uncomfortable with the procedure, it is highly recommended to seek assistance from an experienced mechanic or automotive professional who can accurately diagnose and resolve the issue.

Estimated costs for main repair tasks are as follows:

Remember, these are estimated costs and can vary based on various factors such as location, vehicle model, and labor rates. It is advisable to consult with a professional for accurate cost estimates.

P1605 Toyota Infographic

Wrapping Up

Before we wrap up our discussion on the P1605 Toyota code, let’s take a moment to applaud your commitment to understanding, diagnosing, and fixing the issue. It’s no easy task, but with the right tools, knowledge, and a dash of persistence, you’re well on your way to getting your Toyota back in top shape.

Remember to approach the process step-by-step, examining the air-fuel ratio, intake system, sensors, ignition components, and fuel system. If you ever feel stuck or unsure, don’t hesitate to ask a trusted mechanic for help.

Keep up the great work, and we’re here to support you every step of the way! Share your thoughts or questions below – we’d love to hear from you.

Reference Sources

MotoLogic, 2014 Toyota RAV4 P1603, P1605 Repair Manual