DTC Decoded: P1251 - Toyota Parts Blog
Turbocharger Engine Boost Condition – Limit Exceeded
Check Engine Light Illuminates on Dash and Code is Stored in ECM Bank
Turbo Solenoid Valve
More times than not, the problem that throws this code is with the turbo solenoid valve. Mounted on the driver’s side of the engine near the top, it is a small cylinder shaped plastic unit. This valve also has two vacuum hoses and an electrical connector. This valve operates the wastegate for the turbo and when faulty, it will cause the turbo to over or under charge. Replacement of this valve is almost always a remedy for this problem.
Please note that you should always replace parts such as these with genuine Toyota parts to restore proper function.
NOTE: Toyota doesn’t have too many models from the 1990’s and 2000’s that use a turbo, but that’s going to change beginning in 2015. Toyota is adding a series of new turbocharged models. Stay tuned!