AUTOMATIC TRANSMISSION DIAGNOSIS
AUTOMATIC TRANSMISSION23A-13
A/T DIAGNOSTIC TROUBLESHOOTING STRATEGYM1231007600339
Use these steps to plan your diagnostic strategy. If
you follow them carefully, you will find most A/T mal-
functions.
1. Gather as much information as possible about the
complaint from the customer.
2. Verify that the condition described by the
customer exists.
3. Check the vehicle for any A/T Diagnostic Trouble
Codes (DTCs).
4. If you can not verify the condition and there are no
DTCs, the malfunction is intermittent. For
information on how to cope with intermittent
malfunctions, refer to GROUP 00, How to Use
Troubleshooting/Inspection Service Points
How
to Cope with Intermittent Malfunction P.00-14.
5. If you can verify the condition but there are no
DTCs, or the system can not communicate with
diagnostic tool, refer to the Symptom Chart
P.23A-35.6. If there is a DTC, record the number of the code,
then erase the code from memory using
diagnostic tool.
7. Reconfirm the symptom with a Road Test.
8. If a DTC is set again, go to the Inspection Chart
for Diagnostic Trouble Codes.
9. If a DTC is not set again, the malfunction is
intermittent. For information on how to cope with
intermittent malfunctions, refer to GROUP 00,
How to Use Troubleshooting/Inspection Service
Points
How to Cope with Intermittent
Malfunction P.00-14.
10.After repairs are completed, conduct a Road Test
duplicating the complaint conditions to confirm the
malfunction has been eliminated.
DIAGNOSTIC FUNCTIONM1231022500135
CHECK "N" RANGE LIGHT
The "N" range light flashes once per second if there is an
abnormality in any of the items in the table below which are
related to the A/T system. Check for diagnostic trouble codes if
the "N" range light is flashing once per second.
NOTE: The "N" indicator lamp warning function does not
operate with the selector lever in the "P" (PARK), "R"
(REVERSE) or "N" (NEUTRAL) position.
"N" range light flashing items
Input shaft speed sensor
Output shaft speed sensor
Each solenoid valve
Gear incorrect ratio
A/T control relay system
If the "N" range light is flashing rapidly (twice per second),
the transmission fluid temperature is too high. (It flashes
when the fluid is approximately 125
C or more and goes
off when the fluid is approximately 115
C or less)
ON-BOARD DIAGNOSTICS
The automatic transmission -electronic control unit
(A/T-ECU) monitors its input/output signals (some
signals all the time and others under specified condi-
tions). When an irregular signal is initially monitored,
the A/T-ECU decides that a malfunction has
occurred and records the occurrence as a diagnostic
trouble code. The diagnostic results can be read with diagnostic tool. Diagnostic trouble codes are kept in
memory by direct battery feed. The codes are
retained in memory even if the ignition switch is in
the "LOCK" (OFF) position. DTCs are not erased
even after the battery terminals and the A/T-ECU
connector are disconnected. In addition, the diagnos-
tic trouble code can also be erased by diagnostic
tool.
