Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
DTC Description
With the Air/Fuel Mixture Ratio Self-Learning Control, the actual mixture ratio can be brought closely to the theoretical mixture ratio based on the mixture ratio feedback signal from A/F sensor 1. The ECM calculates the necessary compensation to correct the offset between the actual and the theoretical ratios. In case the amount of the compensation value is extremely large (the actual mixture ratio is too lean), the ECM judges the condition as the fuel injection system malfunction and illuminates the MIL (2 trip detection logic).
| Sensor | Input signal to ECM | ECM function | Actuator |
|---|---|---|---|
| A/F sensor 1 | Density of oxygen in exhaust gas (Mixture ratio feedback signal) | Fuel injection control | Fuel injector |
DTC DETECTION LOGIC
| DTC | CONSULT screen terms (Trouble diagnosis content) | DTC detection condition | |
| P0171-00 | FUEL SYS-LEAN-B1 (System too lean bank 1) | Diagnosis condition | - |
| Signal (terminal) | - | ||
| Threshold |
|
||
| Diagnosis delay time | - | ||
POSSIBLE CAUSE
- Intake air leaks
- A/F sensor 1 (bank 1)
- Fuel injector
- Exhaust gas leaks
- Incorrect fuel pressure
- Lack of fuel
- Mass air flow sensor
- Incorrect PCV hose connection
FAIL-SAFE
Engine Control System
| Fail safe mode | Vehicle behavior | |
|---|---|---|
| Traveling control mode | Accelerator angle variation control | ECM controls the accelerator pedal depression speed to make it slower than actual speed. This causes a drop in accelerating performance and encourages the driver to repair malfunction.
NOTE:
|
| Combustion control mode | Stratified charge combustion control at starting | No stratified charge combustion at starting (cold start). |
| Idle speed control | Stops feedback control of idle speed and controls with specified speed. | |
| Recovery speed control at decelerating | Stops recovery speed control by the fuel cut at decelerating and controls with specified speed. | |
Idle Start/Stop System
When a DTC is detected, the start/stop indicator lamp blinks slowly and the idle start/stop system operation is prohibited. When ECM detects error while operating the idle start/stop system, ECM restarts the engine.
NO RELATED
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Affiliate disclosure: We may earn a commission at no extra cost to you.
When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.