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DTC U1570: No bus activity error for LIN
 
 
cautionWhenever the ECU is replaced, ensure that the power supply circuit, the ground circuit and the communication circuit are normal.
 
 
TROUBLE JUDGMENT
The ETACS-ECU will store DTC No. U1570 when no communication has been carried out for more than a certain period after it received last valid data.
 
 
TROUBLESHOOTING HINTS
  • The ETACS-ECU may be defective
  • The slave ECU may be defective
  • LIN bus lines shorted to power supply
  • LIN bus lines shorted to ground
 
 
DIAGNOSIS
Required Special Tools:
  • MB991223: Harness Set
  • MB992006: Extra Fine Probe
STEP 1. Check of open circuit in LIN line between ETACS-ECU connector and column switch connector.
Is the check result normal?
Go to Step 2.
Repair the connector(s) or wiring harness.
 
STEP 2. Measure the voltage at the LIN bus lines.
Check the LIN bus lines for short to power supply.
(1) Disconnect all the ECU connectors which are connected to the LIN bus lines.
(2) Turn the ignition switch from "LOCK" (OFF) to "ON" position.
(3) Measure the voltage between column switch connector (wiring harness side: DATA terminal) and ground.
  • The voltmeter needle does not swing.
noteIf the LIN bus lines are short to power supply, the voltmeter indicates a constant value.
Is the check result normal?
Go to Step 3.
Repair the connector(s) or wiring harness.
 
STEP 3. Measure the resistance at the LIN bus lines.
Check the LIN bus lines for short to ground.
(1) Disconnect all the ECU connectors which are connected to the LIN bus lines.
(2) Measure the resistance value between column switch connector (wiring harness side: DATA terminal) and ground.
  • No continuity (1 kΩ or more)
Is the check result normal?
Go to Step 4.
Repair the connector(s) or wiring harness.
 
STEP 4. Check the column switch.
Disconnect column switch connector, and recheck whether DTC No. U1570 is set.
(1)
cautionTo prevent damage to scan tool (M.U.T.-III), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool (M.U.T.-III).
Connect scan tool (M.U.T.-III). Refer to "How to connect the Scan Tool (M.U.T.-III) ."
(2) Connect all the relevant ECUs, and disconnect column switch connector only.
(3) Erase the DTC.
(4) Turn the ignition switch from "LOCK" (OFF) to "ON" position.
(5) Check whether DTC No. U1570 is set.
noteIf DTC No. U1570 is not set, DTC No. U1500 is set because the column switch is disconnected. This is normal.
(6) Turn the ignition switch to the "LOCK" (OFF) position.
Is DTC No. U1570 set?
Reconnect the column switch connector, and go to Step 5.
Replace the column switch.
 
STEP 5. Recheck for diagnostic trouble code.
Check again if the DTC is set in the ETACS-ECU.
(1) Erase the diagnostic trouble code.
(2) Turn the ignition switch from "LOCK" (OFF) to "ON" position.
(3) Check whether DTC No. U1570 is set.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is the DTC set?
Replace the ETACS-ECU.
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction ).