DTC 39

DTC 39 Flow Chart:

Torque Converter Clutch Schematic:

CIRCUIT DESCRIPTION
The purpose of the Torque Converter Clutch (TCC) feature is to eliminate the power loss of the torque converter when the vehicle is in a cruise condition. This allows the convenience of the automatic and the fuel economy of a manual transaxle. The heart of the system is two Powertrain Control Module (PCM) controlled solenoids located inside the transaxle.

When the TCC apply solenoid coil is activated "ON", the TCC is applied which results in a straight through mechanical coupling from the engine to the wheels. When the apply solenoid coil is deactivated "OFF", the TCC is released which allows the torque converter to operate in the conventional manner (fluidic coupling between engine and transaxle).
The TCC Pulse Width Modulated (PWM) solenoid is used to vary hydraulic pressure to the converter clutch regulator valve, allowing a smoother engagement of the converter clutch.

Diagnostic Trouble Code (DTC) 39 will set if:
a. TCC is commanded "ON" by the PCM.
b. Vehicle speed is greater than 35 MPH.
c. Throttle angle is 10% or greater.
d. Vehicle is in 3rd or 4th gear.
e. Engine RPM / vehicle speed ratio indicates TCC is not locked.
f. All above conditions exist for longer than 10 seconds.

NOTE: DTC 39 does not illuminate the MIL (Service Engine Soon) light.

TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.

1. Determines whether fault is caused by a bad solenoid or control circuit.
2. Checks availability of battery voltage on circuit 420.
3. Checks the PCM's capability to pulse the PWM solenoid "ON" and "OFF."
4. Electrical circuits have checked out.

DIAGNOSTIC AIDS
The Tech 1 "scan" tool only indicates when the PCM has commanded the TCC driver "ON". This does not confirm that the TCC is actually engaged. To determine if the TCC is engaging properly, road test the vehicle. When the TCC is commanded "ON" by the PCM (as indicated on the "scan" tool display), the engine speed (rpm) should drop slightly. If diagnosis indicates that all electrical circuits and components are OK, slippage may be occuring elsewhere in the transmission, (clutches and / or other mechanical failure.)