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DTC B1731: Engine
Control Module communication timeout
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- When the DTC
B1731 is set, be sure to diagnose the CAN bus line.
- When replacing the ECU, always check that the communication circuit is normal.
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DTC SET CONDITION
KOS-ECU checks that the Engine Control Module data has been received via the CAN bus lines,
and if not, sets the DTC No. B1731.
TECHNICAL DESCRIPTION (COMMENT)
If no data [ETACS transmits engine random number data to KOS-ECU via the CAN
bus lines]
is received from the Engine Control Module via the CAN bus lines when the
ignition switch is turned to ON position, it is judged as abnormal.
TROUBLESHOOTING HINTS
- Malfunction of CAN bus line
- Malfunction of KOS-ECU
- Malfunction of engine control module
- Malfunction of ETACS-ECU
- Damaged wiring harness and connectors
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Required Special Tools:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: Vehicles Communication Interface (V.C.I.)
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A (Vehicles with CAN communication system)
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STEP 1. Using scan tool MB991958, diagnose the CAN bus
line.
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(1)
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To prevent damage to scan tool (MB991958), always turn the ignition switch to the "LOCK" (OFF)
position before connecting or disconnecting scan tool (MB991958).
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Connect scan tool MB991958 to the data link connector.
(2)Turn the ignition switch to the "ON" position.
(3)Diagnose the CAN bus line.
(4)Turn the ignition switch to the "LOCK" (OFF) position.
Q.
Is the CAN bus line found to be normal?
 Go to Step 2.
 Repair the CAN bus line. (Refer to GROUP 54C, Diagnosis  ).
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STEP 2. Using scan tool MB991958, read the Engine Control Module diagnostic
trouble code
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Check again if the DTC is set to the engine control module.
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Troubleshoot the MFI system (Refer to GROUP 13A, Diagnostic trouble code chart <2.0L
Engine Non-turbo>, GROUP 13B, Diagnostic trouble code chart <2.0L
Engine Turbo> or GROUP 13C, Diagnostic trouble code chart <2.4L
Engine> ).
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Go to Step 3.
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STEP 3. Using scan tool MB991958, read the other system diagnostic
trouble code.
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Check if DTC U0100 is set to ETACS-ECU.
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Go to Step 5.
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Go to Step 4.
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STEP 4. Recheck for diagnostic trouble code.
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Check again if the DTC is set to the KOS-ECU.
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(1)Turn the ignition switch from "LOCK" (OFF) position to "ON" position.
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(3)Turn the ignition switch to the "LOCK" (OFF) position.
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Replace KOS-ECU and register the ID codes. (Refer to .)
After registering the ID codes, go to Step 6.
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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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STEP 5. Recheck for diagnostic trouble code.
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Check again if the DTC is set to the KOS-ECU.
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(1)Turn the ignition switch from "LOCK" (OFF) position to "ON" position.
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(3)Turn the ignition switch to the "LOCK" (OFF) position.
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Replace the engine control module and record the VIN (Refer to GROUP 00 - How
To Perform Vehicle Identification Number (VIN) Writing ). Then
go to Step 6.
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The procedure is complete.
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STEP 6. Recheck for diagnostic trouble code.
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Check again if the DTC is set to the WCM.
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(1)Turn the ignition switch from "LOCK" (OFF) position to "ON" position.
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(3)Turn the ignition switch to the "LOCK" (OFF) position.
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Replace the ETACS-ECU.
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The procedure is complete.
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)