Technical Description of OBD-II Trouble Code
Intermittent Circuit Issue with Torque Converter Clutch
This diagnostic trouble code (DTC) is a standard OBD-II powertrain code. It is considered standard because it applies to all makes and models of vehicles (1996-newer), although the specific repair steps may vary depending on the model.
What does that mean?
Modern vehicles with automatic transmissions / transaxles use a torque converter to increase engine torque output and drive the rear wheels.
The engine and transmission are connected by a fluid coupling mechanism inside the torque converter, which multiplies the torque until the speeds equalize and create a “stall” speed where the difference in actual engine RPM and transmission input RPM is around 90% efficient. Torque converter clutch (TCC) solenoids, commanded by the Powertrain control module/Engine control module (PCM/ECM) or the Transmission control module (TCM), direct hydraulic fluid and engage the torque converter clutch to create a solid coupling and increase efficiency.
The transmission control module has detected a fault with the circuit that operates the torque converter clutch solenoid.
Note: This code is similar to codes P0740, P0741, P0742, P0743, P2769, and P2770.
There may be other diagnostic trouble codes associated with the transmission control module that can only be accessed by using an advanced scan tool. If any additional transmission related DTC’s appear in addition to the P0744, an electrical failure is likely.
Symptoms
Symptoms of a P0744 trouble code may include:
Potential Causes
Possible causes of this DTC may include:
Diagnostic Steps for P0744 DTC
Wiring harness – Check the transmission wiring harness for damage or loose connections. Use a factory wiring diagram to locate the appropriate power source and all connection points between circuits. The transmission may be powered by a fuse or relay, and triggered by the TCM. Disconnect the transmission harness at the transmission connector, power source, and TCM. Check for a short to ground inside the transmission internal wiring harness by locating the appropriate + and – pins for the torque converter clutch solenoid.
Using a digital volt ohm meter (DVOM) set to the ohms scale, check for a short to ground in the circuit with the positive lead on either pin and the negative lead to a known good ground. If the resistance is low, suspect a short to ground in the internal harness or the TCC solenoid – removing the transmission oil pan may be necessary to further diagnose the TCC solenoid.
Test the wiring between the TCM and the wiring harness connector at the transmission case using the DVOM set to the ohms scale. Check for a possible short to ground by moving the negative lead on the DVOM to a known good ground, resistance should be very high or over limit (OL).
Test the wiring for the control circuit between the TCM and the wiring harness connector at the transmission case using the DVOM set to the volts scale – it may be necessary to remove the pin from each side of the harness connector to isolate it from the harness while it is still plugged into the TCM and transmission case. With the positive lead on either end of the wiring and the negative lead to a known good ground, check for the presence of battery voltage with the key on/engine off. If voltage is present, suspect a short to power and determine the source of the short circuit in the wire harness assembly.
Hint: Wiggling the wire harness and connectors while testing may help locate an intermittent short to power or ground.
Torque converter clutch (TCC) solenoid – Check the resistance in the TCC solenoid and internal transmission wiring at the transmission case after removing the transmission harness plug (if applicable, some makes/models use a TCM bolted directly to the transmission case). Some makes/models use a transmission wire harness with the TCC solenoid and internal harness as a single unit. The DVOM should be set to the ohms scale with the positive lead and negative lead on the pins for the TCC power and control circuit. Resistance should be within the manufacturer’s specifications, if it is very high or over limit (OL), remove the transmission oil pan to inspect the solenoid inside the transmission if possible.
Check for voltage on the power side circuit of the TCC solenoid with the key on/engine off and harnesses plugged or at the wire harness connector at the TCM with the DVOM set to the volts scale, positive lead on the control side of the solenoid and the negative to a known good ground with the vehicle’s key on/engine off, battery voltage should be present. Tap the solenoid and wiggle the wiring to determine if a short to power or ground exists.
Transmission control module (TCM) – Since the torque converter clutch is only activated during certain driving conditions, it will be necessary to monitor the TCM with an advanced scan tool to determine if the TCM is commanding the TCC solenoid and what the actual feedback reading is at the TCM. The TCC solenoid is normally controlled by a duty cycle to engage a more comfortable torque converter clutch engagement
To test if the TCM is actually sending the signal, a graphing multimeter set to duty cycle or a digital storage oscilloscope will be required as well. The positive lead is probed into the wiring harness plugged into the TCM and the negative lead to a known good ground. The duty cycle should be the same as being commanded by the TCM in the advanced scan tool reading. If the cycle is intermittent on rough road conditions, it may be a wiring fault. Re-check connections and if all wiring / solenoid is OK or if road conditions do not coincide with the intermittent readings, the TCM may be at fault.
