Toyota Forklift Error Code E01-5 Troubleshooting

Toyota Forklift Error Code E01-5: How To Clear This Fault Code?

Toyota Forklift has a diagnostic system that can detect issues such as error code E01-5. This article discusses the E01-5 forklift fault code in detail, its resetting guide, and how to troubleshoot it.

Understanding this error code and its diagnosis will help keep the forklift running smoothly.

Error Code E01-5 on Toyota Forklift

Error Code E01-5 on Toyota Forklift indicates an O2 sensor open abnormality. This means that the oxygen sensor is not receiving the return signal from the computer, which can be caused by a harness defect (broken wire or dirty connectors), a failed O2 sensor, or a defective ECM.

When this error occurs, the engine speed can become unstable or it may even stop. This can limit the speed of traveling and materials handling due to limited engine power output.

An illustration of the portion related to Toyota Forklift Error Code E01-5.

It is therefore important to ensure that the O2 sensor functions properly, to maintain the performance of the engine and keep its operator safe.

Probable Causes

There are 3 main possible causes of the E01-5 error message on the Toyota Forklift:

  1. O2 Sensor defect 
  2. Harness defect 
  3. Engine controller defect

Resetting Guide

Resetting fault code E01-5 can often clear the issue. But if the error persists, it may indicate a faulty part or sensor that needs to be replaced. Here are the steps to reset the error code E01-5 on a Toyota Forklift:

  1. Disconnect the negative terminal of the battery for more than 10 seconds.
  2. Check the connection status of the C1 connector.
  3. Disconnect C1 and perform a visual and contact pressure inspection of the connector.
  4. Short circuit the service connector TC terminal with the E1 terminal.
  5. Connect C1 and the battery negative terminal. Note: For combination vehicles, switch the fuel changeover switch to gasoline.
  6. Turn the ignition key switch ON (engine stopped).
  7. Depress the accelerator pedal 5 times fully (from fully open to fully closed) within 30 seconds.
  8. Start the engine and check that the error has been cleared.
  9. Disconnect the battery negative terminal again.
  10. Disconnect the TC and E1 terminals.
  11. Reconnect the battery negative terminal.
  12. Start the engine and let it idle for a few minutes.
  13. Fully depress the accelerator pedal for 3 minutes with the direction neutral. Then release and leave the accelerator pedal.
  14. Run the engine at idle for 2 minutes.
  15. Repeat steps (13) and (14) for 3 times.
  16. Turn the ignition key switch OFF and leave it off for one minute.
  17. Repeat steps (12 to 16) for 3 times.
  18. This will clear the E01-5 fault code.

Troubleshooting Guide

Resetting the E01-5 error code on your Toyota Forklift is often the solution to the issue. In case resetting this code does not work, troubleshooting the issue can resolve the problem. To troubleshoot the problem, you should follow the inspection process in sequential order.

1). Connector Contact Inspection

The connector is a crucial component in a forklift’s electrical system that helps to establish a reliable connection between different parts of the system. It plays a critical role in ensuring that the various electrical signals are transmitted accurately and consistently, which is essential for the proper functioning of the forklift.

A defective Connector contact could result in triggering the e015-error code on Toyota Forklift. Its fix typically involves replacing the damaged component with a new one.

👉 If the error code is resolved, it’s good.
Otherwise, move to the next inspection step below.

2). Harness Continuity and Short Circuit Inspection

The harness continuity refers to the uninterrupted flow of electrical signals through the wiring harness of the forklift. To ensure proper forklift performance, it’s important to address any breakage or damage in the harness, which could result in issues such as the e01-5 error code.

To inspect for continuity and short-circuiting of the harness, it is necessary to turn off the ignition key switch and disconnect the A35 and C1 connectors. This will allow for a thorough inspection of the wiring harness.

Standard readings are:

A35-20 ~ C1-3Continuity
A35-21 ~ C1-4Continuity
A35-20 ~ FrameNo Continuity

The fix would be to repair or replace the damaged harness to ensure the uninterrupted flow of electrical signals.

👉 If the error code is resolved, it’s good.
Otherwise, move to the next inspection step below.

3). O2 Sensor Inspection for Connector Contact Defect

The O2 sensor voltage inspection is a diagnostic procedure used to determine if the oxygen (O2) sensor in a Toyota forklift is functioning correctly.

The O2 sensor measures the amount of oxygen in the exhaust gas to help the engine control system adjust the air/fuel mixture for optimal combustion.

The connector connection plays a crucial role in transmitting the voltage signal from the O2 sensor to the engine control module. A faulty connector can cause voltage signal interference, leading to the engine control system receiving incorrect readings.

  1. To inspect the O2 sensor voltage output, start by connecting A35 and C1. 
  2. Then, start the engine and let it warm up completely. 
  3. Set the direction to neutral and fully press the accelerator pedal. 
  4. Measure the O2 sensor voltage using the I/O monitor: OX. 
  5. The Standard Voltage Readings should be: OX 0.4 V or less and 0.5 V or more alternately output. 
  6. If the readings are outside of this range, then there may be a problem with the connectors that connect the O2 sensor to the ECM.

👉 If the error code is resolved, it’s good.
Otherwise, move to the next inspection step below.

4). O2 Sensor Voltage Inspection for Engine Controller Defect

If the connector contact is functioning properly, you can assess any defects in the engine controller by taking O2 sensor voltage readings.

In the case of a Toyota forklift, an engine controller defect may trigger an error code, as it regulates the air-fuel mixture and monitors the O2 sensor’s output.

An engine controller defect can cause the check engine light to appear, and E01-5 or E01-1 or E01-2 codes to be generated due to incorrect voltage levels in the O2 sensor readings.

To inspect the output of an O2 sensor in a Toyota forklift for checking engine controller defect, you can follow these steps:

  1. Disconnect the C1 connector.
  2. Connect a voltmeter or an oscilloscope probe to pin A35 of the connector.
  3. Start the engine and let it warm up completely.
  4. Set the direction of the forklift in neutral.
  5. Fully open the accelerator pedal.
  6. Read the O2 sensor voltage on the voltmeter or oscilloscope.
  7. The standard voltage readings should be OX 0.2 V or less (I/O monitor: OX).


The Toyota Forklift’s E01-5 error code provides valuable information about the specific issue affecting the O2 sensor. By identifying an open abnormality in the sensor, the error code helps diagnose potential problems such as a faulty harness due to dirty connectors or broken wires, a malfunctioning O2 sensor, or a flawed ECM. This allows for targeted and effective troubleshooting to restore the forklift’s optimal functioning. While resetting the fault code may sometimes fix the problem, persistent occurrences may indicate the need to replace a defective part or sensor.

To identify the issue, the article recommends examining the connector contact, testing the harness for continuity and short-circuits, and inspecting the O2 sensor for connector contact issues. To ensure optimal performance, it is recommended to check the engine controller if the issue persists.

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