Chart C-8A Torque Converter Clutch (TCC) Electrical Diagnosis

CIRCUIT DESCRIPTION
The purpose of the automatic transmission Torque Converter Clutch (TCC) feature is to eliminate the power loss of the torque converter stage when the vehicle is in a cruise condition. This allows the convenience of the automatic transmission and the fuel economy of a manual transmission.

Fused battery ignition is supplied to the TCC solenoid through the TCC brake switch. a

The ECM will engage TCC by grounding CKT 422 to energize the solenoid.

TCC will engage when:
^ Vehicle speed above 30 mph (48 km/h).
^ Engine at normal operating temperature (above 65°C/149°F)
^ Throttle Position Sensor (TPS) output not changing, indicating a steady road speed.
^ Brake switch closed.
^ 3rd or 4th gears.

TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. A test light "ON" indicates battery voltage and continuity through the TCC solenoid is OK.
2. Checks for vehicle speed sensor signal to ECM using a "Scan" tool.

DIAGNOSTIC AIDS
Solenoid coil resistance must measure more than 20 ohms. Less resistance will cause early failure of the ECM "Driver." Refer to "ECM QDR" check CHART C-1A in "Electronic Control Module (ECM) and Sensors." Using an ohmmeter, check the sole noid coil resistance of all ECM controlled solenoids and relays before installing a replacement ECM. Replace any solenoid or relay that measures less than 20 ohms resistance. Chart C-1A Park/Neutral Switch Diagnosis

To prevent TCC over heat condition TCC, temperature switch closes at 279°F and reopens at 259°F.