Check Engine p0046

[boon_up]

Hi. A month ago got Check Engine with p0046:Turbocharger / Supercharger Boost Control "A" Circuit Range.
As an immediate consequences - rpm were limited by 2000 by Toyota computer. After 1-2 starts during next 3 days error got away but on next day it was there again(

Got a scanner. Turned out MAF sensor values were rather OK, but MAP values with engine off showed 77 kPa (27 Hin) instead of smth close to barometric pressure around 99 kPa (29 Hin), almost no change in value with engine start. Engine on idle is stable. While driving sensor values were changing almost as expected.

First - air and MAP sensor filters were changed for new ones - no result, MAF and MAP sensors cleaned - no result. Bought cheap analog for Toyota original MAP sensor - NTY ECM-TY-005. Strangely the value of new MAP sensor without engine on changed for 185 kPa. Then I made reset for ECU - no change. No other visible problems found (tubes, cables, turbo itself - all seem good).

Could anybody recommend any other way to solve the problem or to make some different tests?

Thanks in advance!

[ptommo59]

Hi boon_up,

Firstly switch back to your original OEM MAP sensor as the low reading is most likely your Scantool (it is a common issue with them reading around 20kPa low due to a scaling error when using the Toyota Mode 21 MAP sensor parameter).

The Boost control is via the actuator assembly on the side of the Turbo and the P0046 is telling you the actuator motor is drawing too much current or staying at 100% duty cycle.
So either:
* Your variable vanes inside the turbo are jammed due to soot build up inside the turbo.
* The actuator arm on the outside is jammed.
* There is a short in the wiring to the actuator motor.
* The turbo actuator motor is faulty.
* The turbo motor driver assembly that controls the motor is faulty.

To isolate the first two, turn your ignition on without starting the engine and you should hear and see the actuator arm moving on the side of the turbo. If its not moving freely try to lubricate the externals and gently work the arm to see if it frees up.
To check for shorts, with the ignition off disconnect the two pin connector to the actuator motor and check if you have a short on either side (actuator side should normally read between 1 and 100 ohms)
If there is a short on the connector side that runs back to the vehicle check if something has burned or rubbed through the harness.
If short is on the actuator side you are most likely up for a replacement motor (the Turbo actuator with motor can be source separate for the complete turbo at various outlets).

Hope this helps .

[boon_up]

Hi boon_up,

Firstly switch back to your original OEM MAP sensor as the low reading is most likely your Scantool (it is a common issue with them reading around 20kPa low due to a scaling error when using the Toyota Mode 21 MAP sensor parameter).

The Boost control is via the actuator assembly on the side of the Turbo and the P0046 is telling you the actuator motor is drawing too much current or staying at 100% duty cycle.
So either:
* Your variable vanes inside the turbo are jammed due to soot build up inside the turbo.
* The actuator arm on the outside is jammed.
* There is a short in the wiring to the actuator motor.
* The turbo actuator motor is faulty.
* The turbo motor driver assembly that controls the motor is faulty.

To isolate the first two, turn your ignition on without starting the engine and you should hear and see the actuator arm moving on the side of the turbo. If its not moving freely try to lubricate the externals and gently work the arm to see if it frees up.
To check for shorts, with the ignition off disconnect the two pin connector to the actuator motor and check if you have a short on either side (actuator side should normally read between 1 and 100 ohms)
If there is a short on the connector side that runs back to the vehicle check if something has burned or rubbed through the harness.
If short is on the actuator side you are most likely up for a replacement motor (the Turbo actuator with motor can be source separate for the complete turbo at various outlets).

Hope this helps .

Thanks a lot. I'll try things you suggest.