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5A-68 AUTOMATIC TRANSMISSION Description / Cause The signal from the mode switch is unreliable. This fault is caused by too many changes in the mode input signal over a period of time. Typical causes would be an intermittent connec tion in the switch or wiring or an intermittent short to ground in the wiring. The data link between the TCU and the engine management module is found to be unreliable because the checksum, or the data received, did not match the correct checksum. This could be caused by an open circuit, short circuit to ground or a loose connection in the link wire itself. Each solenoid in turn is switched off if it was energised, or switched on if it was not energised by a very small 100 ms pulse. This pulse is too short for the solenoid to react so transmission operation is not af fected. The solenoid feedback voltage is measured before the 100 ms pulse and again during the pulse. If the difference is outside the acceptable limits the relevant fault messages are set. Typical causes would be an open circuit in the wiring to or within the solenoid, or a short circuit to ground in the wiring to, from or within the solenoid in question. If several of these fault codes are presents check the wiring or connectors that are common to the selected solenoids, especially the earth connections. The state of the solenoid feedback voltage is outside acceptable limits but the faulty solenoid could not be isolated. The current to solenoid 5 was outside acceptable limits. This fault results from a mismatch between the current set point for solenoid 5 and the current measured by the feedback within the TCU. Typical causes would be an open circuit or short circuit to ground in the wiring to, from or within the solenoid. It is also possible that there has been a fault in the solenoid output circuit. If this is the case however, the fault should be continually present. The closed throttle position has not been learnt. This fault may be caused by the transmission not having reached normal operating temperature or the engine idle speed being incorrect. The TCU will learn the closed throttle position automatically when the transmission is brought to normal operating temperature and the engine is allowed to idle in Drive with the ‘base idle’ correctly set and the air conditioner (if fitted) switched off. Condition Mode Switch Input Fault (Power/Economy Mode) Data Output Link Fault On/off Solenoid Fault (Solenoid 1,2,3,4,6,7) Solenoid 5 Fault (Variable Pressure Solenoid) Throttle Not Learnt Solenoid 9 10 11 12 13 |