Pontiac Fiero 1988 Service Manual page 565

6E2-C8-4 DRIVEABILITY A M D EMISSIONS - FUEL INJECTION (TBI)
ECM
I.P. HARNESS CONNECTOR
15 W A Y . (FRONT VIEW)
I —
420 PPL
AUTO
TRANSMISSION
(125 C)
5-1-87
15-WAY I.P.
CONNECTOR
— » —
BRAKE
SWITCH
IGN
N.C.
PNK/
BLK
39
GAGE
t
3 R D GEAR OIL
APPLY SWITCH.
(CLOSES IN 3 r d
GEAR)
m—
TAN/BLK 422
T C C
SOLENOID
H
^ 1 5 - W A Y I.P.
V C O N N E C T O R
TCC
CONTROL
DRIVER
ALDL CONNECTOR
* 7 S 3 3 1 1 - 6 E
4-21-87
CHART C-8A
125C TRANSMISSION CONVERTER CLUTCH (TCC)
(ELECTRICAL DIAGNOSIS)
231 "P" SERIES (TBI)
Circuit Description:
The purpose of the automatic transmission torque converter clutch 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
transmission and the fuel economy of a manual transmission.
Fused battery ignition is supplied to the TCC solenoid through the brake switch and transmission third
gear apply switch. 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 70°C, 156°F).
Throttle position sensor output not changing, indicating a steady road speed.
Transmission third gear switch closed.
Brake switch closed.
Test Description:
Numbers below refer to circled 3.
numbers on the diagnostic chart. 4.
1. Light "OFF" confirms transmission third gear
apply switch is open.
2. At 48 km/h (30 mph), the transmission third gear
switch should close. Test light will come on and
confirm battery supply, and close brake switch.
3. Grounding the diagnostic terminal, with engine
"OFF", should energize the TCC solenoid. This
test checks the capability of the ECM to control
the solenoid.
Check TCC solenoid resistance as follows:
1. Disconnect TCC at transmission.
2. Connect ohmmeter between transmission
connector, opposite harness connector terminal
"A" and "D".
5.
Raise drive wheels.
Run engine in drive about 48 km/h (30 mph) to
close third gear apply switch.
Replace the TCC solenoid, and ECM, if resistance
measures less than 20 ohms, when switch is
closed.
Diagnostic Aids:
An engine coolant thermostat that is stuck open,
or opens at too low a temperature, may result in an
inoperative TCC.