U1702

DTC U1702: Communication error in the front-ECU

NOTE:
This troubleshooting procedure requires the use of scan tool MB991958 and SWS monitor kit MB991813. For details on how to use the SWS monitor, refer to "How to use SWS monitor How to Use SWS Monitor."

CAUTION:
If DTC U1702 is set in the ETACS-ECU, always diagnose the CAN main bus line.

TROUBLE JUDGMENT

The ETACS-ECU communicates with the front-ECU through the SWS communication line. If there is any trouble in that communication, DTC U1702 will be set.

TECHNICAL DESCRIPTION (COMMENT)

Current trouble

- The front-ECU, the ETACS-ECU, connector(s), or wiring harness between the two may be defective.
Past trouble

- If DTC U1702 is set as past trouble, carry out diagnosis with particular emphasis on wiring and connector(s) between the front-ECU and the ETACS-ECU or power supply to the front-ECU. For diagnosis procedures, refer to "How to cope with past trouble" How to Treat Past Trouble ).

TROUBLESHOOTING HINTS

- The wiring harness or connectors may have loose, corroded, or damaged terminals, or terminals pushed back in the connector.

DIAGNOSIS

Required Special Tools:

- MB991223: Harness Set
- MB992006: Extra Fine Probe
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A
- MB991813: SWS Monitor Kit
- MB991806: SWS Monitor Cartridge
- MB991812: SWS Monitor Harness (For Column-ECU)
- MB991822: Probe Harness

STEP 1. Using scan tool MB991958, diagnose the CAN bus line.





(1)
CAUTION:
To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.

Connect scan tool MB991958. Refer to "How to connect SWS monitor How to Connect SWS Monitor."
(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?

YES Go to Step 2.

NO Repair the CAN bus line CAN Bus Diagnostics Chart).

STEP 2. Recheck for diagnostic trouble code.





Check again if the DTC is set.
(1)Erase the DTC.
(2)Turn the ignition switch to the "ON" position.
(3)Check if the DTC is set.
(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the DTC set?

YES Go to Step 3.

NO There is an intermittent malfunction such as poor engaged connector(s) or open circuit How to Cope With Intermittent Malfunctions).

STEP 3. Use scan tool MB991958 to select "ECU COMM Check" on the SWS monitor display.

Check the following ECUs:

- Front-ECU
- ETACS-ECU









(1)
CAUTION:
Connect special tool MB991910 before connecting special tool MB991812. Be sure to connect special tool MB991806 after turning on special tool MB991824.

Connect the SWS monitor. Refer to "How to connect SWS monitor How to Connect SWS Monitor."
(2)Turn the ignition switch to the "LOCK" (OFF) position.
(3)Operate scan tool MB991958 according to the procedure below to display "ECU COMM Check."

.....Select "Interactive Diagnosis."

.....Select "System select."

.....Select "SWS."

.....Select "SWS MONITOR."

.....Select "ECU COMM Check."
(4)Scan tool MB991958 should show "OK" on the "ECU COMM Check" menus for both the "ETACS ECU" and the "FRONT ECU" menus.

Q. Are "OK" displayed for both the "ETACS ECU" and "FRONT ECU" menus?

"OK" are displayed for all the items : It is determined that there is an intermittent malfunction such as poor engaged connector(s) or open circuit How to Cope With Intermittent Malfunctions).

"NG" is displayed for the "ETACS ECU" menu : Refer to Inspection Procedure A-3 "Communication with the ETACS ECU is not possible Inspection Procedure A-3."

"NG" is displayed for the "FRONT ECU" menu : Refer to Inspection Procedure A-4 "Communication with the front-ECU is not possible Inspection Procedure A-4."