P1749

P1749-TRANSMISSION THROTTLE F VALVE POSITION SENSOR CIRCUIT LOW

For the Transmission circuit diagram Refer to Transmission Control Systems/Diagrams.
For a complete wiring diagram refer to 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:
Continuously with the ignition on.
- Set Condition:
When the Engine Control Module (ECM) detects the monitored Transmission Throttle Valve Position Sensor voltage drops below a predetermined value.

Possible Causes

- (K312) TTVA POSITION SENSOR SIGNAL CIRCUIT OPEN
- (K312) TTVA POSITION SENSOR SIGNAL CIRCUIT SHORT TO GROUND
- (K312) TTVA POSITION SENSOR SIGNAL CIRCUIT SHORT TO ANOTHER CIRCUIT
- (F856) 5 VOLT SUPPLY CIRCUIT OPEN
- (F856) 5 VOLT SUPPLY CIRCUIT SHORT TO GROUND
- (F856) 5 VOLT SUPPLY CIRCUIT SHORT TO ANOTHER CIRCUIT
- TRANSMISSION THROTTLE VALVE ACTUATOR
- ENGINE CONTROL MODULE

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.

Diagnostic Test
1. CHECK THE TTVA

Turn the ignition off to the lock position.
Disconnect the ECM C1 and C2 harness connectors.
Measure the resistance of the (K312) TTVA Position Sensor Signal circuit between the ECM C1 harness connector and the TTVA harness connector.

Is the resistance below 5.0 ohms?
Yes >>Go To 3
No >>Repair the (K312) TTVA Position Sensor Signal circuit for an open.
Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). Verification Tests

3. CHECK THE (K312) TTVA POSITION SENSOR SIGNAL CIRCUIT FOR A SHORT TO GROUND

Measure the resistance between ground and the (K312) TTVA Position Sensor Signal circuit.

Is the resistance below 5.0 ohms?
Yes >>Repair the (K312) TTVA Position Sensor Signal circuit for a short to ground.
Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). Verification Tests
No >>Go To 4

4. CHECK THE (K312) TTVA POSITION SENSOR SIGNAL CIRCUIT FOR A SHORT TO ANOTHER CIRCUIT

Measure the resistance between the (K312) TTVA Position Sensor Signal circuit and all other circuits in the ECM C1 and C2 harness connectors.

Is the resistance below 100 k ohms between the (K312) TTVA Position Sensor Signal circuit and any other circuit(s) in the ECM C1 or C2 harness connectors.
Yes >>Repair the (K312) TTVA Position Sensor Signal circuit for a short to another circuit(s).
Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). Verification Tests
No >>Go To 5

5. CHECK THE (F856) 5 VOLT SUPPLY CIRCUIT FOR AN OPEN

Measure the resistance of the (F856) 5-volt Supply circuit between the ECMC2 harness connector and the TTVA harness connector.

Is the resistance below 5.0 ohms?
Yes >>Go To 6
No >>Repair the (F856) 5-volt Supply circuit for an open.
Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). Verification Tests

6. CHECK THE (F856) 5 VOLT SUPPLY CIRCUIT FOR A SHORT TO GROUND

Measure the resistance between ground and the (F856) 5-volt Supply circuit.

Is the resistance below 5.0 ohms?
Yes >>Repair the (F856) 5-volt Supply circuit for a short to ground.
Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). Verification Tests
No >>Go To 7

7. (F856) 5 VOLT SUPPLY CIRCUIT SHORT TO ANOTHER CIRCUIT

Measure the resistance between the (F856) 5-volt Supply circuit and all other circuits in the ECM C1 and C2 harness connectors.

Is the resistance below 100 k ohms between the (F856) 5-volt Supply circuit and any other circuit(s) in the ECM C1 or C2 harness connectors.
Yes >>Repair the (F856) 5-volt Supply circuit for a short to another circuit(s).
Perform RE TRANSMISSION VERIFICATION TEST VER 1 (DIESEL). Verification Tests
No >>Go To 8

8. CHECK THE TTVA

Ignition on, engine not running. With the scan tool, record and erase Engine DTCs. Turn the ignition off to the lock position. Disconnect the TTVA harness connector.

NOTE: Check connectors - Clean/repair as necessary.

Connect a jumper wire between the (K312) TTVA Position Sensor Signal circuit and the (F856) 5-volt Supply circuit in the TTVA harness connector.
Ignition on, engine not running.
With the scan tool, read Engine DTCs.

Did the DTC P1750-Transmission Throttle Valve Position Sensor Circuit High set?
Yes >>Go To 9
No >>Using the schematics as a guide, check the Engine Control Module (ECM) pins, terminals, and connectors for corrosion, damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems are found, replace and program the ECM per the Service Information.
Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). Verification Tests

9. INTERMITTENT WIRING AND CONNECTORS
The conditions necessary set this DTC are not present at this time.
Use the Freeze Frame Data to help duplicate the conditions that set the DTC. Pay particular attention to the DTC set conditions, such as, VSS, MAP, ECT, and Load.
Visually inspect the related wiring harness. Look for any chafed, pierced, pinched, or partially broken wires.
Visually inspect the related wiring harness connectors. Look for broken, bent, pushed out, or corroded terminals.
Refer to any technical service bulletins that may apply.

Were there any problems found?
Yes >>Repair as necessary.
Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). Verification Tests
No >>Test Complete.