4AT(diag)-77
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
AUTOMATIC TRANSMISSION (DIAGNOSTICS)
4
CHECK HARNESS CONNECTOR BETWEEN
TCM AND TRANSMISSION.
Measure the resistance of harness between
TCM connector and chassis ground.
Connector & terminal
(B54) No. 15 — Chassis ground:
Is the resistance 1 M
: or
more?
Go to step 5.
Repair the short
circuit of harness
between TCM and
rear vehicle speed
sensor connector.
5
CHECK HARNESS CONNECTOR BETWEEN
TCM AND TRANSMISSION.
Measure the resistance of harness between
TCM connector and chassis ground.
Connector & terminal
(B54) No. 26 — Chassis ground:
Is the resistance 1 M
: or
more?
Go to step 6.
Repair the short
circuit of harness
between TCM and
rear vehicle speed
sensor connector.
6
PREPARE OSCILLOSCOPE.
Do you have an oscilloscope?
Go to step 8.
Go to step 7.
7
CHECK INPUT SIGNAL FOR TCM.
1) Connect the connectors to TCM and trans-
mission.
2) Lift up the vehicle.
3) Start the engine and set vehicle in 20 km/h
(12 MPH) condition.
NOTE:
The speed difference between front and rear
wheels may illuminate the ABS warning light,
but this does not indicate a malfunction. When
AT control diagnosis is finished, perform the
ABS or VDC clear memory of on-board diag-
nostics system. <Ref. to ABS(diag)-20, Clear
Memory Mode.> <Ref. to VDC(diag)-23, Clear
Memory Mode.>
4) Measure the AC voltage between TCM con-
nector terminals.
Connector & terminal
(B54) No. 26 (+) — No. 15 (–):
Is the voltage approx. 2 V or
more?
Go to step 9.
Replace the rear
vehicle speed sen-
sor.
8
CHECK INPUT SIGNAL FOR TCM USING
OSCILLOSCOPE.
1) Connect the connectors to TCM and trans-
mission.
2) Lift up the vehicle.
3) Set the oscilloscope to TCM connector ter-
minals.
Connector & terminal
Positive probe; (B54) No. 26:
Ground lead; (B54) No. 15:
4) Start the engine and set vehicle in 20 km/h
(12 MPH) condition.
NOTE:
The speed difference between front and rear
wheels may illuminate the ABS warning light,
but this does not indicate a malfunction. When
AT control diagnosis is finished, perform the
ABS or VDC clear memory of on-board diag-
nostics system. <Ref. to ABS(diag)-20, Clear
Memory Mode.> <Ref. to VDC(diag)-23, Clear
Memory Mode.>
5) Measure the signal voltage indicated on
oscilloscope.
Is the pulse voltage approx. 5 V? Go to step 9.
Replace the rear
vehicle speed sen-
sor.
9
CHECK POOR CONTACT.
Is there poor contact in rear
vehicle speed sensor circuit?
Repair the poor
contact.
Replace the TCM.
<Ref. to 4AT-61,
Transmission Con-
trol Module
(TCM).>
Step
Check
Yes
No