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P1753






P1753-TRANSMISSION THROTTLE VALVE MECHANICAL PERFORMANCE





For a complete wiring diagram refer to Diagrams/Electrical. Electrical Diagrams


Theory of Operation


The transmission throttle valve cable has been replace by the transmission throttle valve actuator (TTVA). The TTVA consists of an electric DC motor, two potentiometers, and a gear drive system. The TTVA is mechanically connected to the transmission throttle valve in the valve body by the "D" shaped opening in the bottom of the TTVA shaft.


The Transmission Throttle Valve Actuator (TTVA) does not require any mechanical adjustments. All changes in throttle valve position are controlled by the Engine Control Module (ECM).


The TTVA does require an initialization period after the actuator has been removed or replaced. After the actuator has been removed or replaced, move the ignition to the ON position for thirty (30) seconds. This will allow the ECM sufficient time to perform the internal calibration procedures to learn the TTVA's current "zero" position.


- When Monitored:

Ignition on, engine running in a valid forward gear with a throttle opening greater than 50% and the transmission in overdrive.

- Set Condition:

When the Governor pressure is below a minimum threshold when conditions indicate that the Governor pressure should be high. This DTC indicates that the TTVA is working properly electronically but mechanically the output shaft is not moving the Throttle Valve in the transmission.







Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Checkout (Diesel)


Diagnostic Test


1. CHECK FOR GOVERNOR PRESSURE DTCS

Ignition on, engine not running.

With the scan tool, check Engine DTCs.

Are there any Governor Pressure related DTCs present?

Yes

- Refer to the Transmission category and perform the appropriate symptom(s).

No

- Go To 2



2. CHECK TTVA FOR SIGNS OF DAMAGE

Turn the ignition off to the lock position.

Visually inspect the TTVA shaft for any signs of external damage or improperly mounted.


NOTE: It is not necessary to remove the TTVA to perform this procedure.



Is the TTVA damaged or improperly mounted?

Yes

- Repair as necessary.
- Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). Transmission Verification Test

No

- Go To 3



3. CHECK IF TTVA SHAFT END IS DAMAGED

Turn the ignition off to the lock position.

Remove the TTVA from the transmission.

Inspect the end of the TTVA shaft for cracks or damage.


NOTE: The end of the TTVA should be keyed or "D" shaped and fit tightly over the Throttle Valve shaft.

Is the end of the TTVA shaft undamaged and fit tightly over the Throttle Valve shaft?

Yes

- Go To 4

No

- Inspect the Throttle Valve shaft on the transmission for free movement. If the Throttle valve does not move freely, inspect internal transmission components related to the Throttle Valve and replace as necessary. Replace the TTVA in either case.
- Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). Transmission Verification Test



4. CHECK THE TRANSMISSION THROTTLE VALVE ACTUATOR

Properly support the TTVA to where the end of the shaft can be observed and reconnect the TTVA wiring harness.


NOTE: Each time the ignition is cycled to the on position, the ECM commands a TTVA internal calibration procedure (autozero) to determine the zero position. Do not press on the accelerator pedal during this test.

Ignition on, engine not running.

Observe the output shaft of the TTVA during the autozero procedure.

After completion of the autozero procedure, while observing the TTVA shaft, press the accelerator pedal to full throttle.

Does the TTVA internal motor move the TTVA shaft?

Yes

- Inspect the Throttle Valve shaft on the transmission for free movement. If the Throttle valve does not move freely, inspect internal transmission components related to the Throttle Valve and repair or replace as necessary.
- Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). Transmission Verification Test

No

- Replace the TTVA.
- Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). Transmission Verification Test