Code No.U1570 No bus activity error for LIN
TROUBLE JUDGEMENT
The ETACS-ECU will set diagnosis code No. U1570 when no communication has been carried out for more than a certain period after it received last valid data.
PROBABLE CAUSES
- Malfunction of the ETACS-ECU
- Malfunction of the slave ECU
- LIN bus lines shorted to power supply
- LIN bus lines shorted to earth
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STEP 1. Check the following wiring harness.
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- Check of open circuit in LIN line between ETACS-ECU connector and column switch connector.
- Check of open circuit in LIN line between ETACS-ECU connector and lighting control sensor connector. <Vehicles with auto lamp>
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Q.
Are all the wiring harness wires in good condition?
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 Go to Step 2.
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 Repair the connector(s) or wiring harness.
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STEP 2. Measure the voltage at the LIN bus lines.
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Check the LIN bus lines for short to power supply.
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(1)Disconnect all the ECU connectors which are connected to the LIN bus lines.
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(2)Turn the ignition switch from "LOCK" (OFF) to "ON" position.
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(3)Measure the voltage between column switch connector (wiring harness side: DATA terminal) and earth.
- The voltmeter needle does not swing.
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If the LIN bus lines are short to power supply, the voltmeter indicates a constant value.
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Q.
Is the check result normal?
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Go to Step 3.
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Repair the connector(s) or wiring harness.
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STEP 3. Measure the resistance at the LIN bus lines.
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Check the LIN bus lines for short to earth.
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(1)Disconnect all the ECU connectors which are connected to the LIN bus lines.
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(2)Measure the resistance value between column switch connector (wiring harness side: DATA terminal) and earth.
- No continuity (1 kΩ or more)
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Q.
Is the check result normal?
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Go to Step 4.
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Repair the connector(s) or wiring harness.
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STEP 4. Check the column switch.
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Disconnect column switch connector, and recheck whether diagnosis code No. U1570 is set.
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(1)Connect all the relevant ECUs, and disconnect column switch connector only.
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(2)Erase the diagnosis code.
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(3)Turn the ignition switch from "LOCK" (OFF) to "ON" position.
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(4)Check whether diagnosis code No. U1570 is set.
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If diagnosis code No. U1570 is not set, diagnosis code No. U1500 is set because the column switch is disconnected. This is normal.
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(5)Turn the ignition switch to the "LOCK" (OFF) position.
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Q.
Is diagnosis code No. U1570 set?
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YES <Vehicles with auto lamp> : Reconnect the column switch connector, and go to Step 5.
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YES <Vehicles without auto lamp> : Reconnect the column switch connector, and go to Step 6.
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Replace the column switch (Refer to GROUP 54A - Column switch  ).
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STEP 5. Check the lighting control sensor.
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Disconnect lighting control sensor connector, and recheck whether diagnosis code No. U1570 is set.
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(1)Connect all the relevant ECUs, and disconnect lighting control sensor connector only.
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(2)Erase the diagnosis code.
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(3)Turn the ignition switch from "LOCK" (OFF) to "ON" position.
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(4)Check whether diagnosis code No. U1570 is set.
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If diagnosis code No. U1570 is not set, diagnosis code No. U1504 is set because the lighting control sensor is disconnected. This is normal.
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(5)Turn the ignition switch to the "LOCK" (OFF) position.
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Q.
Is diagnosis code No. U1570 set?
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Reconnect the lighting control sensor connector, and go to Step 6.
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Replace the lighting control sensor (Refer to GROUP 51 - Lighting control sensor ).
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STEP 6. Recheck for diagnosis code.
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Check again if the diagnosis code is set in the ETACS-ECU.
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(1)Erase the diagnosis code.
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(2)Turn the ignition switch from "LOCK" (OFF) to "ON" position.
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(3)Check whether diagnosis code No. U1570 is set.
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(4)Turn the ignition switch to the "LOCK" (OFF) position.
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Q.
Is the diagnosis code set?
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Replace the ETACS-ECU (Refer to GROUP 54A - ETACS-ECU ).
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The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction ).
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