What P1128 means
This is a diagnostic trouble code (DTC) reported by your vehicle's onboard OBD-II system when a specific fault is detected in the powertrain.
Common causes (general)
Before spending money on parts, verify the code with a scan tool and read freeze frame data. Freeze frame captures every sensor value at the moment the code set — this is often enough to figure out the root cause without further testing.
Manufacturer-specific descriptions
Different manufacturers use this code for slightly different failure modes. Here's what your specific make means by P1128:
| ACURA | MAP Lower Than Expected |
| CHRYSLER | Closed Loop Fueling Not Achieved - Bank 1; Upstream Heated Oxygen Sensor Signals Reversed |
| FORD | Upstream Heated Oxygen Sensor Signals Reversed |
| HONDA | Manifold Absolute Pressure (MAP) Sensor Circuit Lower Than Expected |
| INFINITI | MAP Lower Than Expected |
| KIA | Long Term Fuel Trim Multiplicative Air System High |
| LEXUS | Throttle Control Motor Lock Malfunction |
| LINCOLN | Upstream Heated Oxygen Sensor Signals Reversed |
| MAZDA | HO2S Bank 1 Sensor 1 Signals Swapped In Key On Engine Running Self Test |
| MERCURY | Upstream Heated Oxygen Sensor Signals Reversed |
| MITSUBISHI | Upstream Heated O2 Sensors Swapped |
| NISSAN | Upstream Heated O2 Sensors Swapped; Throttle Control Motor |
| OTHER | Upstream Heated O2 Sensors Swapped |
| TOYOTA | Throttle Control Motor Lock |
| VOLKSWAGEN | Long Term Fuel Trim mult.,Bank1 System too Lean |
Read this code on your own car
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