Fuel System Over Pressure
OBD-II code P1229 represents a problem with the pressure of your Toyota's fuel system.
Fuel must come through lines at an ideal pressure to keep your engine running properly. A fault in the system can cause the system to over fuel and increase pressure beyond the ideal range. The fuel system on your Toyota is controlled by the fuel pressure regulator and most problems with over-fueling will come from this part or wiring to it. When there is a problem with pressure in the system, a trouble code from the vehicle's ECM is stored; when the problem is too much pressure, the dashboard will illuminate the SES or check engine light to indicate that code P1229 has been stored in your vehicle's ECM.
The most common causes of this code are:
- Defective fuel pressure regulator
- Fuel pressure regulator stuck open
- Faulty wiring/fuel pump wiring
- Faulty ECM
The symptoms of a defective fuel pressure regulator usually include a lack of fuel pressure, but it has been known to also increase fuel pressure instead. Much of the time, if your system is overloaded with fuel, the regulator is stuck open -- this causes the engine to become flooded with fuel, resulting in poor performance and backfiring. Another common culprit is the wiring for the fuel pump. If all other problems have been determined to not be at fault, it is possible, but unlikely, that the ECM is faulty. Some problems of a faulty ECM include stalling, loss of power, and erratic shifting for automatics.
For a comprehensive list of trouble codes, check out this article on the Toyota Parts Center Blog.