# U0401 on the 2017 Mazda CX\-9

The bulletins listed name this code in NHTSA's summary, or are about the same components. A bulletin or a recall listed here may apply to the model year. None of it is a diagnosis.

Nobody has written a description of this code yet.

## Bulletins for this model year that name U0401

- [10143970](https://open.wenmarpro.com/bulletins/10143970), 2018-08-20: Some vehicles may exhibit an engine misfire during acceleration with the check engine light flashing and the following DTC\(s\). P0302:00 \- Cylinder No.2 misfire detected and/or P0303:00 \- Cylinder No.3 misfire detected NOTE: Even if a misfire occurred, the DTCs may not be stored because they are set after the continuous misfire occurred for 2 drive cycles. In this case, check if the following information is available to verify if the vehicle is applicable to this Service Information. The customer states that the misfire occurred and at the same time the check engine light started flashing. DTC U0401:00 \(\(ABS\) Signal error from PCM\) is detected.This concern may be caused if the exhaust manifold variable valve shaft \(1\) is out of alignment and/or the exhaust manifold variable valve housing \(2\) is out of shape. The exhaust manifold variable valve \(3\) then interferes with the housing and becomes stuck closed when the engine is hot. To eliminate this concern in the future, the production processes and controls have been improved.
- [10136771](https://open.wenmarpro.com/bulletins/10136771), 2018-05-14: Some vehicles may exhibit an engine misfire during acceleration with the check engine light flashing and the following DTC\(s\). P0302:00 \- Cylinder No.2 misfire detected and/or P0303:00 \- Cylinder No.3 misfire detected NOTE: Even if a misfire occurred, the DTCs may not be stored because they are set after the continuous misfire occurred for 2 drive cycles. In this case, check if the following information is available to verify if the vehicle is applicable to this Service Information. The customer states that the misfire occurred and at the same time the check engine light started flashing. DTC U0401:00 \(\(ABS\) Signal error from PCM\) is detected. This concern may be caused if the exhaust manifold variable valve shaft \(1\) is out of alignment and/or the exhaust manifold variable valve housing \(2\) is out of shape. The exhaust manifold variable valve \(3\) then interferes with the housing and becomes stuck closed when the engine is hot. To eliminate this concern in the future, the production processes and controls have been improved.
- [10129350](https://open.wenmarpro.com/bulletins/10129350), 2018-02-26: Some customers may experience a lack of power when driving. The master warning light or the check engine light turns on and DTC P130C:00 and U0401:00 \(ABS\) stored in memory. It occurs mostly at low temperatures. Once the ignition is turned off and on, the concern may disappear. NOTE: DTC P130C:00 may not be found upon M\-MDS self test since this DTC is detected when the condition occurs in two drive cycles in a row. The PCM turns the master warning light on during the first drive cycle, then stores a pending DTC. The master warning light and check engine light come on in the second drive cycle as a confirmation of the DTC. The engine power is limited by the fail\-safe function both in the first and second drive cycles. DTC P130C:00 \- \(Pre\-ignition detected\), DTC U0401:00\- \(ABS\) \(Signal error from PCM\) Improper control logic of the PCM detects a normal operating noise as a knocking noise. To eliminate this concern, the control logic of the PCM has been changed.