P1128 Code - Closed Loop Fueling Not Achieved Bank 1
Quick Answer
The Powertrain Control Module (PCM) detects a condition where the vehicle has remained in open loop fuel control, from a start-up condition, longer than a calibrated amount of time, when conditions would have otherwise closed loop operation. Common causes include Fuel delivery system, Manifold Absolute Pressure (MAP) sensor or wiring connectors, O2 sensor wiring or connectors. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
- What it means
- P1128 indicates Closed Loop Fueling Not Achieved Bank 1.
- Common causes
- Common causes include Fuel delivery system, Manifold Absolute Pressure (MAP) sensor or wiring connectors, O2 sensor wiring or connectors.
- Severity
- High - diagnose this code as soon as possible.
- Can I drive?
- Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
Code P1128 Description
What are the Possible Causes of the DTC P1128?
- Fuel delivery system
- Manifold Absolute Pressure (MAP) sensor or wiring connectors
- O2 sensor wiring or connectors
- Engine mechanical system
- Faulty Powertrain Control Module (PCM)
How to Fix the DTC P1128?
Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.
What is the Cost to Diagnose the Code?
Labor: 1.0
To diagnose the P1128 code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.
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Information for Specific Makes
- P1128 Acura — Manifold Absolute Pressure Sensor Signal Lower Than Expected
- P1128 Audi — Long Term Fuel Trim B1 System Too Lean
- P1128 Chrysler — Closed Loop Fueling Not Achieved Bank 1
- P1128 Dodge — Closed Loop Fueling Not Achieved Bank 1
- P1128 Ford — Front O2 Sensor Connectors Swapped
- P1128 Honda — Manifold Absolute Pressure Sensor Signal Lower Than Expected
- P1128 Hyundai — Fuel System Lean Part Load
- P1128 Infiniti — Throttle Control Motor Circuit Short
- P1128 Isuzu — MAP Sensor Voltage Lower Than Expected
- P1128 Jeep — Closed Loop Fueling Not Achieved Bank 1
- P1128 Lexus — Throttle Control Motor Lock Malfunction
- P1128 Lincoln — Front O2 Sensor Connectors Swapped
- P1128 Mazda — HO2S Heater O2 Sensor Too Cool Before KOER Test
- P1128 Mercury — Front O2 Sensor Connectors Swapped
- P1128 Mitsubishi — Closed Loop Fueling Not Achieved Bank 1
- P1128 Nissan — Throttle Control Motor Circuit Short
- P1128 Toyota — Throttle Control Motor Lock Malfunction
- P1128 Volkswagen — Long Term Fuel Trim B1 System Too Lean
Frequently Asked Questions about P1128 Code
1. What are the common symptoms of OBDII code P1128?
- Common symptoms include poor fuel economy, rough idling, engine stalling, and a noticeable decrease in overall performance.
2. What are the possible causes of OBDII code P1128?
- Possible causes include a faulty oxygen sensor, vacuum leaks, issues with the fuel delivery system, a malfunctioning mass airflow sensor, or a problem with the engine coolant temperature sensor.
3. How can I diagnose the root cause of OBDII code P1128?
- Diagnosing the issue typically involves conducting a thorough inspection of the oxygen sensor, checking for vacuum leaks, testing the fuel pressure, examining the mass airflow sensor, and verifying the engine coolant temperature sensor's functionality.
4. Can a clogged fuel filter trigger OBDII code P1128?
- Yes, a clogged fuel filter can disrupt the fuel delivery system and contribute to the occurrence of OBDII code P1128.
5. What are some repair tips for addressing OBDII code P1128?
- Repair tips may include replacing the oxygen sensor, fixing any vacuum leaks, cleaning or replacing the mass airflow sensor, ensuring proper fuel pressure, and verifying the engine coolant temperature sensor's accuracy.
6. Is it safe to continue driving with OBDII code P1128 present?
- It is not recommended to continue driving with this code active, as it can lead to further damage to the engine and negatively impact vehicle performance.
7. Can resetting the OBDII system clear OBDII code P1128?
- Resetting the OBDII system may temporarily clear the code, but it is crucial to address the underlying issue causing the code to prevent it from reoccurring.
8. How can I prevent OBDII code P1128 from appearing in the future?
- Regular maintenance of your vehicle, including timely replacement of oxygen sensors, fuel filters, and other key components, can help prevent the recurrence of OBDII code P1128.
9. Will OBDII code P1128 cause my vehicle to fail an emissions test?
- Yes, OBDII code P1128 can cause your vehicle to fail an emissions test due to the impact it has on fuel efficiency and emissions control.
10. Is it necessary to consult a professional mechanic to address OBDII code P1128?
- While some DIY repairs may be possible, consulting a professional mechanic is recommended to accurately diagnose and address the underlying issues triggering OBDII code P1128.
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