Automotive Function Diagnosis
The Engine & ECT ECU is equipped with a built-in self diagnostic system, which allows the technician to easily and quickly locate malfunctioning parts or circuitry during troubleshooting of the ECT. The ECU detected a malfunction makes a diagnosis and memorizes the failed section.
HINT:
In some models, the “O/D OFF” indicator light blinkswhen the ECU detects a malfunction.When the O/D main switch is OFF, the “O/D OFF”indicator light will remain on in the event of a malfunction,but it will not blink.
There is no O/D OFF indicator light in models equipped with a gate type shift lever. Consequently, the driving pattern indicator light blinks to warn the driver.
The MIL (Malfunction Indicator Lamp) turns on when a malfunction is detected in the speed sensor, solenoid valve, or their circuits.
2. Memory function
Once a malfunction is stored in the ECU memory system, it will be retained until cancelled even after the malfunction has been corrected.
Once a malfunction is stored by the ECU, back-up current from the battery will keep it retained in memory even if the ignition switch is turned OFF.
3. Diagnostic codes
The DTCs (Diagnostic Trouble Codes) are stored in memory. The DTCs can be read by connecting a hand-held tester to the DLC3 to communicate with the ECU directly or causing a short between the TE1(TC) and E1(CG) terminals of the DLC and observing the blinking pattern of the MIL. The DTCs can be cleared by connecting the handheld tester to the DLC3 or removing a specified fuse with the ignition switch OFF. For details, refer to the Repair Manual.
Fail-Safe
The Engine & ECT ECU has several failsafe functions to allow the vehicle to continue running even if a malfunction occurs in the electrical system during driving.
1. Solenoid valve back-up function
The vehicle can continue running if either one or both of the No.1 and No.2 solenoid valves malfunctions. This is because the ECU controls the transaxle using the solenoid valve that has not malfunctioned. Furthermore, if both solenoid valves malfunction, the driver can still drive the vehicle by operating the shift lever manually.
HINT:
The gear controlled by the fail-safe differs depending on the model.
2. Back-up speed sensing function
If the speed sensor becomes faulty, the ECU performs shift control by using the engine speed signal instead of the vehicle speed signal. In this case, control is much rougher than that under normal circumstances.
3. Manual operation function
If the electronic control system becomes totally deactivated for some reason, the ECT allows the gears to be mechanically shifted to the shift lever position.
2 Responses to “Automotive Function Diagnosis”
By nori on Apr 30, 2010 | Reply
i want documentation concerning modern cars differnt sensors and how they function
By nori on Apr 30, 2010 | Reply
i would like receive kindly from you documentation concerning modern cars their sensors how they work and how we remediat