DTC P0743. Cadillac Catera 2001

For 1990-2009 cars only

Makes 🢒 Cadillac 🢒 2001 🢒 Catera 🢒 Transmission/Transaxle 🢒 Automatic Transmission - 4L30-E 🢒 DTC P0743

Master Electrical Component List
Automatic Transmission Controls Schematics
OBD II Symbol Description Notice

Circuit Description

The torque converter clutch (TCC) solenoid is located in the transmission adapter case. The solenoid valve controls the engagement and disengagement of the torque converter clutch in 3rd and 4th gears. The TCC operation is dependent on transmission fluid temperature, selected shift program, and vehicle speed.

The transmission control module (TCM) provides voltage to the solenoid through an internal solid-state relay. The TCM uses a second driver to control the solenoid ground circuit. The ground control driver reports feedback voltage to the TCM. When the TCM commands the TCC ON, the voltage of the control circuit should be approximately 0 volts. When the TCM commands the TCC OFF, the voltage of the circuit should be approximately the system voltage. When the TCM detects a continuous open, short to ground, or a short to power in the TCC solenoid circuit or in the TCC solenoid valve, then DTC P0743 sets. DTC P0743 is a type B DTC.

Conditions for Running the DTC

•	The TCC is commanded OFF.

•	The TCM high side driver is closed.

Conditions for Setting the DTC

•	A short to ground:

TCM detects less than 2.45 volts for 0.18 seconds on the control circuit.

•	Open circuit:

TCM detects 2.45-3.53 volts for 0.18 seconds on the control circuit.

•	Short to battery:

TCM detects more than 4.02 volts for 0.18 seconds on the control circuit.

Action Taken When the DTC Sets

•	The TCM flashes the sport mode lamp and sends a MIL request to the ECM on the second consecutive drive trip that the diagnostic runs and fails. The ECM then illuminates the MIL.

•	The ECM records the operating conditions in the Freeze Frame at the time of the MIL request from the TCM.

•	The transmission operates in the default mode (maximum line pressure, command 4th gear, inhibit TCC, freeze shift adapts).

Conditions For Clearing the MIL/DTC

•	The ECM turns off the MIL after three consecutive drive trips during which the TCM sends no MIL request.

•	A History DTC clears after forty consecutive warm-up cycles, if no failures are present by this diagnostic or any other emission related diagnostic.

•	The scan tool clears the MIL/DTC.

•	The TCM cancels the DTC default mode actions when the ignition switch is Off long enough in order to power down the TCM.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

Listen for an audible click when the solenoid energizes.

Step

Action

Value(s)

Yes

Did you perform Powertrain On Board Diagnostic (OBD) System Check - Automatic Transmission ?

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check - Automatic Transmission

Install the Scan Tool .
Turn ON the ignition with the engine OFF.

Important: Record the Failure Records before clearing the DTCs. Using the Clear Info function erases the Failure Records from the ECM and the TCM.

Record the DTC Freeze Frame and Failure Records.
Clear the DTC.
Use the Scan Tool in order to command the TCC Solenoid ON.

Does the solenoid operate?

Go to Step 9

Go to Step 3

Turn OFF the ignition.
Disconnect the transmission adapter case 4-way harness connector.
Install the J 44539 jumper harness to the TCM side of the 4-way connector.
Turn ON the ignition with the engine OFF.
Use the Scan Tool in order to command the Power Control Relay ON.
With the J 35616-200 test light connected to ground, probe the TCM Power Relay output circuit (terminal D) of the jumper harness.

Does the test light illuminate?

Go to Step 4

Go to Step 7

Turn OFF the ignition.
Connect the J 44539 to the transmission side of the 4-way connector.
Measure the resistance between terminals A and D of the jumper harness with the J 39200 .

Refer to Component Resistance .

Is the resistance within the specified range?

Go to Step 5

Go to Step 8

Measure the resistance between terminal A of the J 44539 and a good ground on the transmission case with the J 39200 .

Is the resistance greater than the specified value?

50K ohms

Go to Step 6

Go to Step 8

Caution: When you are performing service on or near the SIR components or the SIR wiring, you must disable the SIR system. Refer to Disabling the SIR System. Failure to follow the correct procedure could cause air bag deployment, personal injury, or unnecessary SIR system repairs.

Turn OFF the ignition.
Disconnect the TCM.
Test the TCC Solenoid Valve Control circuit (CKT FB738) for the following conditions:

•	Open circuit. Refer to Testing for Continuity in Wiring Systems.

•	Short to voltage. Refer to Testing for a Short to Voltage in Wiring Systems.

•	Short to ground. Refer to Testing for Short to Ground in Wiring Systems.

Did you find a condition?

Go to Step 10

Go to Step 9

Turn OFF the ignition.
Disconnect the TCM.
Test the TCM Power Relay output circuit from the TCC Solenoid to the TCM (CKTs PF854 and PF754) for an open circuit. Refer to Testing for Continuity in Wiring Systems.

Did you find a condition?

Go to Step 10

Go to Step 9

Remove the adapter case oil pan.
Test the TCC solenoid wiring from the adapter case connector to the TCC solenoid connector for the following conditions: