Mitsubishi Lancer (4A9 engine). Manual - part 142

REVERSING SENSOR SYSTEM

CHASSIS ELECTRICAL

54A-230

YES : 

Replace the corner sensor/back sensor-

ECU.

NO : 

Replace the rear corner sensor (RH).

STEP 5. Diagnosis code recheck
Temporarily replace the rear corner sensor (LH), and 
then check if the diagnosis code No. B2531 is set.

Q: Is the diagnosis code set?

YES : 

Replace the corner sensor/back sensor-

ECU.

NO : 

Replace the rear corner sensor (LH).

STEP 6. Diagnosis code recheck
Temporarily replace the back sensor (RH), and then 
check if the diagnosis code No. B2533 is set.

Q: Is the diagnosis code set?

YES : 

Replace the corner sensor/back sensor-

ECU.

NO : 

Replace the back sensor (RH).

STEP 7. Diagnosis code recheck
Temporarily replace the back sensor (LH), and then 
check if the diagnosis code No. B2535 is set.

Q: Is the diagnosis code set?

YES : 

Replace the corner sensor/back sensor-

ECU.

NO : 

Replace the back sensor (LH).

Code No.U0001 Bus off (CAN-C)

CAUTION

• If there is any problem in the CAN bus lines, 

an incorrect diagnosis code may be set. Prior 
to this diagnosis, always diagnose the CAN 
bus lines.

• Before replacing the ECU, ensure that the 

power supply circuit, the earth circuit and the 
communication circuit are normal.

DIAGNOSTIC FUNCTION
This diagnosis code is set when corner sensor/back 
sensor-ECU has ceased the CAN communication 
(bus off).

JUDGEMENT CRITERIA
The corner sensor/back sensor-ECU judges the bus-
off error.

PROBABLE CAUSES

• Malfunction of the corner sensor/back sensor-

ECU

• Malfunction of wiring harness or connector

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnostics
Use the M.U.T.-III to diagnose the CAN bus lines.

Q: Is the check result normal?

YES : 

Go to Step 2.

NO : 

Repair the CAN bus line (Refer to GROUP 
54C 

− Troubleshooting ).

STEP 2. Check whether the diagnosis code is 
reset.
Check again if the diagnosis code is set to the corner 
sensor/back sensor-ECU.
(1) Erase the diagnosis code.
(2) Turn the ignition switch from "LOCK" (OFF) 

position to "ON" position.

(3) Check if diagnosis code is set.

Q: Is the diagnosis code set?

YES : 

Replace corner sensor/back sensor-ECU.

NO : 

The trouble can be an intermittent 
malfunction (Refer to GROUP 00 

− How to 

use Troubleshooting/inspection Service 
Points 

− How to Cope with Intermittent 

Malfunction ).

REVERSING SENSOR SYSTEM

CHASSIS ELECTRICAL

54A-231

Code No. U0100 Engine-ECU CAN timeout

CAUTION

• If the diagnosis code No. U0100 is set, be sure 

to diagnose the CAN bus line.

• Before replacing the ECU, ensure that the 

power supply circuit, the earth circuit and the 
communication circuit are normal.

DIAGNOSTIC FUNCTION
The corner sensor/back sensor-ECU sets diagnosis 
code No.U0100 when it cannot receive signals from 
the engine ECU.

JUDGEMENT CRITERIA
The corner sensor/back sensor-ECU cannot receive 
the signal from the engine-ECU via the CAN bus line.

PROBABLE CAUSES

• Malfunction of CAN bus line

• Malfunction of engine-ECU

• Malfunction of corner sensor/back sensor-ECU

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnostics
Use the M.U.T.-III to diagnose the CAN bus lines.

Q: Is the check result normal?

YES : 

Go to Step 2.

NO : 

Repair the CAN bus line (Refer to GROUP 
54C 

− Troubleshooting ).

STEP 2. M.U.T.-III other system diagnosis code
Check if diagnosis code is set to the engine-ECU.

Q: Is the diagnosis code set?

YES : 

Troubleshoot the engine (Refer to GROUP 

13A 

− Diagnosis Code Chart  <1600>, 

GROUP 13B 

− Diagnosis Code Chart  

<1800-PETROL-DOHC, 2000>, GROUP 
13C 

− Diagnosis Code Chart  <DIESEL> or 

GROUP 13F 

− Diagnosis Code Chart  

<1800-SOHC>).

NO : 

Go to Step 3.

STEP 3. Check the M.U.T.-III Diagnosis code for 
other systems
Check if the diagnosis code No. U0100 is set to 
ETACS-ECU.

Q: Is the diagnosis code set?

YES : 

Go to Step 4.

NO : 

Go to Step 5.

STEP 4. Diagnosis code recheck
Check again if the diagnosis code is set to the corner 
sensor/back sensor-ECU.
(1) Erase the diagnosis code.
(2) Turn the ignition switch from the LOCK (OFF) 

position to the ON position.

(3) Check if the diagnosis code is set.

Q: Is the diagnosis code set?

YES : 

Replace the engine-ECU.

NO : 

A poor connection, open circuit, or other 
intermittent malfunction in the CAN bus line 
between the corner sensor/back sensor-
ECU and the engine-ECU. (Refer to 
GROUP 00 

− How to Use Troubleshooting/

Inspection Service Points - How to Cope 
with Intermittent Malfunction .)

STEP 5. Diagnosis code recheck
Check again if the diagnosis code is set to the head-
lamp automatic levelling-ECU.
(1) Erase the diagnosis code.
(2) Turn the ignition switch from the LOCK (OFF) 

position to the ON position.

(3) Check if the diagnosis code is set.

Q: Is the diagnosis code set?

YES : 

Replace the corner sensor/back sensor-

ECU.

NO : 

A poor connection, open circuit, or other 
intermittent malfunction in the CAN bus line 
between the corner sensor/back sensor-
ECU and the engine-ECU. (Refer to 
GROUP 00 

− How to Use Troubleshooting/

Inspection Service Points - How to Cope 
with Intermittent Malfunction .)

REVERSING SENSOR SYSTEM

CHASSIS ELECTRICAL

54A-232

Code No.U0121 ASC/ABS-ECU CAN timeout

CAUTION

• If the diagnosis code No. U0121 is set, be sure 

to diagnose the CAN bus line.

• Before replacing the ECU, ensure that the 

power supply circuit, the earth circuit and the 
communication circuit are normal.

DIAGNOSTIC FUNCTION
The corner sensor/back sensor-ECU sets diagnosis 
code No.U0121 when it cannot receive signals from 
the ABS-ECU or ASC-ECU.

JUDGEMENT CRITERIA
The corner sensor/back sensor-ECU cannot receive 
the signal from the ABS-ECU or ASC-ECU via the 
CAN bus line.

PROBABLE CAUSES

• Malfunction of CAN bus line

• Malfunction of ABS-ECU or ASC-ECU

• Malfunction of corner sensor/back sensor-ECU

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnostics
Use the M.U.T.-III to diagnose the CAN bus lines.

Q: Is the check result normal?

YES : 

Go to Step 2.

NO : 

Repair the CAN bus line (Refer to GROUP 
54C 

− Troubleshooting ).

STEP 2. M.U.T.-III other system diagnosis code
Check if diagnosis code is set to the ABS-ECU or 
ASC-ECU.

Q: Is the diagnosis code set to the any of the above?

Set to the ABS-ECU. : 

Troubleshoot the ABS. 

Refer to GROUP 35B 

− Troubleshooting .

Set to the ASC-ECU. : 

Troubleshoot the ASC. 

Refer to GROUP 35C 

− Troubleshooting .

NO : 

Go to Step 3.

STEP 3. Check the M.U.T.-III Diagnosis code for 
other systems
Check if the diagnosis code No. U0121 is set to 
ETACS-ECU.

Q: Is the diagnosis code set?

YES : 

Go to Step 4.

NO : 

Go to Step 5.

STEP 4. Diagnosis code recheck
Check again if the diagnosis code is set to the corner 
sensor/back sensor-ECU.
(1) Erase the diagnosis code.
(2) Turn the ignition switch from the LOCK (OFF) 

position to the ON position.

(3) Check if the diagnosis code is set.

Q: Is the diagnosis code set?

YES : 

Replace the ABS-ECU or ASC-ECU.

NO : 

A poor connection, open circuit, or other 
intermittent malfunction in the CAN bus line 
between the corner sensor/back sensor-
ECU and the ABS-ECU or ASC-ECU. 
(Refer to GROUP 00 

− How to Use 

Troubleshooting/Inspection Service Points - 
How to Cope with Intermittent Malfunction .)

STEP 5. Diagnosis code recheck
Check again if the diagnosis code is set to the corner 
sensor/back sensor-ECU.
(1) Erase the diagnosis code.
(2) Turn the ignition switch from the LOCK (OFF) 

position to the ON position.

(3) Check if the diagnosis code is set.

Q: Is the diagnosis code set?

YES : 

Replace the corner sensor/back sensor-

ECU.

NO : 

A poor connection, open circuit, or other 
intermittent malfunction in the CAN bus line 
between the corner sensor/back sensor-
ECU and the ABS-ECU or ASC-ECU. 
(Refer to GROUP 00 

− How to Use 

Troubleshooting/Inspection Service Points - 
How to Cope with Intermittent Malfunction .)

REVERSING SENSOR SYSTEM

CHASSIS ELECTRICAL

54A-233

Code No. U0141 ETACS-ECU CAN timeout

CAUTION

• If the diagnosis code No. U0141 is set, be sure 

to diagnose the CAN bus line.

• Before replacing the ECU, ensure that the 

power supply circuit, the earth circuit and the 
communication circuit are normal.

DIAGNOSTIC FUNCTION
The corner sensor/back sensor-ECU sets diagnosis 
code No.U0141 when it cannot receive signals from 
the ETACS-ECU.

JUDGEMENT CRITERIA
The corner sensor/back sensor-ECU cannot receive 
the signal from the ETACS-ECU via the CAN bus 
line.

PROBABLE CAUSES

• Malfunction of CAN bus line

• Malfunction of ETACS-ECU

• Malfunction of corner sensor/back sensor-ECU

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnostics
Use the M.U.T.-III to diagnose the CAN bus lines.

Q: Is the check result normal?

YES : 

Go to Step 2.

NO : 

Repair the CAN bus line (Refer to GROUP 
54C 

− Troubleshooting ).

STEP 2. M.U.T.-III other system diagnosis code
Check again if the diagnosis code is set to the 
ETACS-ECU.

Q: Is the diagnosis code set?

YES : 

Troubleshoot the ETACS-ECU. (Refer to 

GROUP 54A 

− ETACS-ECU − 

Troubleshooting .)

NO : 

Go to Step 3.

STEP 3. Check the M.U.T.-III Diagnosis code for 
other systems
Check if the diagnosis code No. U0141 is set to 
engine-ECU.

Q: Is the diagnosis code set?

YES : 

Go to Step 4.

NO : 

Go to Step 5.

STEP 4. Diagnosis code recheck
Check again if the diagnosis code is set to the corner 
sensor/back sensor-ECU.
(1) Erase the diagnosis code.
(2) Turn the ignition switch from the LOCK (OFF) 

position to the ON position.

(3) Check if the diagnosis code is set.

Q: Is the diagnosis code set?

YES : 

Replace the ETACS-ECU.

NO : 

A poor connection, open circuit, or other 
intermittent malfunction in the CAN bus line 
between the corner sensor/back sensor-
ECU and the ETACS-ECU. (Refer to 
GROUP 00 

− How to Use Troubleshooting/

Inspection Service Points - How to Cope 
with Intermittent Malfunction .)

STEP 5. Diagnosis code recheck
Check again if the diagnosis code is set to the corner 
sensor/back sensor-ECU.
(1) Erase the diagnosis code.
(2) Turn the ignition switch from the LOCK (OFF) 

position to the ON position.

(3) Check if the diagnosis code is set.

Q: Is the diagnosis code set?

YES : 

Replace the headlamp automatic levelling-

ECU.

NO : 

A poor connection, open circuit, or other 
intermittent malfunction in the CAN bus line 
between the corner sensor/back sensor-
ECU and the ETACS-ECU. (Refer to 
GROUP 00 

− How to Use Troubleshooting/

Inspection Service Points - How to Cope 
with Intermittent Malfunction .)