Toyota Forklift 01-01 Code: Fuel Feedback Error (Rich)

The 01-01 code on Toyota forklifts with 4Y-ECS gasoline engines indicates a fuel feedback control error (rich mixture). This serious fault causes unstable engine speed and can result in the engine stalling.

What Does 01-01 Mean?

The forklift's engine control system detects the fuel mixture is too rich (too much fuel, not enough air). This imbalance prevents proper combustion and causes performance issues.

Common Symptoms:

• Engine speed fluctuates or surges
• Engine may stall or refuse to idle
• Poor fuel economy
• Black smoke from exhaust
• Rough running or hesitation

Common Causes

1. O2 Sensor Failure - Most common cause; sensor provides incorrect feedback
2. Intake System Defects - Air leaks or blockages affecting air/fuel ratio
3. Exhaust Restrictions - Clogged catalytic converter or muffler
4. Fuel System Issues - Leaking injectors or high fuel pressure
5. Wiring Harness Defects - Damaged or corroded sensor wiring
6. Engine Controller Fault - ECU malfunction (rare)

How to Fix Code 01-01

1. Replace O2 Sensor (Most Common Solution)

The oxygen sensor is the most frequent culprit. If sensor is over 3 years old or shows irregular voltage, replace it. Cost: $80-200 for sensor + labor.

2. Repair Intake/Exhaust Leaks

Inspect all vacuum hoses, intake manifold gaskets, and exhaust connections. Even small leaks can trigger this code.

3. Clean or Replace Air Filter

Restricted airflow from dirty filter can cause rich condition. Check and replace if needed.

4. Check Fuel Injectors

Leaking or stuck-open injectors dump excess fuel. Professional cleaning or replacement may be needed.

Resetting the Code

1. Turn ignition off
2. Disconnect battery negative terminal for 30 seconds
3. Reconnect battery
4. Turn ignition on (don't start)
5. Code should clear if issue is resolved

Note: If code returns immediately, the underlying problem hasn't been fixed.