Troubleshooting
TROUBLESHOOTINGCAUTIONS REGARDING FAIL-SAFE FUNCTION
The TCM has an electrical fail-safe mode. This mode makes it possible to operate safe driving even though a input/output signal circuit of electronic controls has been compromised. Under the fail-safe mode, the select lever is fixed in 2nd, 4th or 5th gear (depending on malfunction position) either being "D" or "M" Range, so customers should feel "slipping" or "poor accelerating".
Transmission can go into the fail-safe mode under the special conditions even when electronic circuit is normal. In such a case, turn key switch OFF and ON again after 5 seconds so that you can return to normal shift pattern.
Therefore the vehicle can go back to normal function, so handle according to "Diagnosis flow". performing self diagnosis results in:
At first, vehicle speed sensor 1 or vehicle speed sensor 2 indicates. No indication after the second time of self diagnosis after having checked sensors.
FAIL-SAFE FUNCTION
If any malfunction occurs in each sensor or solenoid, this function controls the A/T to make driving possible.
INPUT/OUTPUT SIGNAL OF TCM
Vehicle speed sensor 1 (The output shaft rotation sensor)
^ Signals are input from two systems from vehicle speed sensor 1 (revolution sensor) installed on the transmission and from combination meter.
Accelerator sensor signal
^ If an error occurs in the accelerator sensor signal, detect accelerator opening angle in response to accelerator angle opening signal (input according to CAN communication) that is transmitted from ECM, control line pressure as below to enable driving.
Inhibitor switch
^ If an abnormal signal enters TCM, turn range indicator OFF and N-P relay OFF (Starter start disabled), and the position is fixed to the "D" range to make driving possible.
N-P relay
^ Turn N-P relay OFF (Starter start disabled)
A/T Inter lock determination
If there is an A/T Inter lock judgment malfunction, fix to 2nd, 4th, or 5th gear so that driving is enabled.
CAUTION:
It will indicate a turbine sensor error when driving with 2nd gear or 5th gear on, but turbine sensor has no problem.
When the coupling pattern below is detected, the fail-safe action corresponding to the pattern is performed
A/T INTER LOCK ENGAGEMENT PATTERN TABLE
A/T 1st gear engine braking
^ If there is an A/T 1st gear engine brake judgment malfunction, turn OFF the low coast brake solenoid so that the engine brake does not operate.
Line pressure solenoid
^ Turn solenoid OFF and make line pressure maximum so that driving is enabled.
Lock-up solenoid
^ Turn solenoid OFF and release lock-up.
Low coast brake solenoid
^ If an error occurs in solenoid ON (electrical, functional errors), fix to 2nd gear, and if OFF, fix to 4th gear so that driving is enabled.
Input clutch solenoid
^ If an error occurs in solenoid ON or OFF (electrical, functional errors), fix to 4th gear so that driving is enabled.
Direct clutch solenoid
^ If an error occurs in solenoid ON or OFF (electrical, functional errors), fix to 4th gear so that driving is enabled.
Front brake clutch solenoid
^ If an error occurs in solenoid ON (electrical error), fix to 5th gear, and if OFF (electrical error), fix to 4th gear so that driving is enabled.
^ If an error occurs in solenoid ON (functional error), fix to 2nd gear, and if OFF (functional error), fix to 4th gear so that driving is enabled.
High & low reverse clutch solenoid
^ If an error occurs in solenoid ON, OFF (electrical, functional errors), fix to 4th gear so that driving is enabled.
Turbine sensor 1, 2
^ The control is the same as if there were no turbine revolution sensors, 5th gear is prohibited.
Troubleshooting procedures
To perform failure diagnosis faster and more accurately, it is crucial to exactly understand what is the problem. Generally each customer takes in the same problem in a different way. It is necessary to exactly understand trouble symptoms or the conditions for a customer complaint.
To perform the best troubleshooting possible, utilize information from customer and diagnosis sheet.
To start
^ TCM receives a signal from vehicle speed sensor, accelerator sensor, inhibitor switch and controls shift and lock-up by solenoid valve, Therefore, input/output signal shall be exactly stable during A/T operation. And, there shall be no problem with valve and solenoid valve for A/T system to normally operate.
^ It is more difficult to diagnose troubles that occur intermittently rather than continuously. Many intermittent troubles can be caused by electrical connection or wiring failures. In such cases, check thoroughly the relevant circuits and take caution not to replace normal part by mistake.
6 A visual check only may not find the cause for the errors. A road test with hi-scan or circuit tester connected should be performed.
^ When there is a trouble with driveability, take a few minutes to talk with customers before checking. Especially, it is expected to obtain information that is helpful to diagnose the intermittent errors.
^ Find out what symptoms are present and under what conditions they occur using the diagnostic sheet.
^ Start your diagnosis by looking for conventional errors first. This will help troubleshoot driveability errors on an electronically controlled engine vehicle.