Introduction
NCAT0023
The TCM receives a signal from the vehicle speed sensor, throttle
position sensor or PNP switch and provides shift control or lock-up
control via step motor and CVT solenoid valves.
The TCM also communicates with the ECM by means of a signal
sent from sensing elements used with the OBD-related parts of the
CVT system for malfunction-diagnostic purposes. The TCM is
capable of diagnosing malfunctioning parts while the ECM can
store malfunctions in its memory.
Input and output signals must always be correct and stable in the
operation of the CVT system. The CVT system must be in good
operating condition and be free of valve seizure, solenoid valve
malfunction, etc.
It is much more difficult to diagnose a problem that occurs intermit-
tently rather than continuously. Most intermittent problems are
caused by poor electric connections or improper wiring. In this
case, careful checking of suspected circuits may help prevent the
replacement of good parts.
A visual check only may not find the cause of the problems. A road
test with CONSULT-II (or GST) or a circuit tester connected should
be performed. Follow the “Work Flow”. Refer to AT-32.
Before undertaking actual checks, take a few minutes to talk with
a customer who approaches with a driveability complaint. The cus-
tomer can supply good information about such problems, espe-
cially intermittent ones. Find out what symptoms are present and
under what conditions they occur. A “Diagnostic Worksheet” like the
example (AT-31) should be used.
Start your diagnosis by looking for “conventional” problems first.
This will help troubleshoot driveability problems on an electronically
controlled engine vehicle.
Also check related Service bulletins for information.
SAT631IA
Sensors
TCM
ECM
Solenoid valves
SAT632I
INFO.
CAUSE
SEF234G
TROUBLE DIAGNOSIS — INTRODUCTION
Introduction
AT-29