Mitsubishi Lancer Evolution IX. Manual — part 405
TROUBLESHOOTING
MULTIPORT FUEL INJECTION (MPI)
13A-95
Code No. P0141: Oxygen Sensor Heater (rear) System
OPERATION
• Power is supplied to the heater power terminal
(terminal No. 3) of the oxygen sensor (rear) con-
nector from the engine control relay (terminal No.
4).
• The heater (terminal No. 4) of the oxygen sensor
(rear) connector is controlled by the power tran-
sistor in the engine-ECU (terminal No. 26).
1
2
3
4
AK501808
3 4
2
1
2
3 4
5 6
7 8
9
11 12 13 14 15 16 17 18 19 20
30
21 22 23
24 25
26 27 28 29
3132 33
34 35
1
10
B-12X
B-Y
B-Y
B-Y
R-Y
Oxygen sensor (rear)
3
2
4
1
To engine-ECU
Engine-ECU
26
L-Y
R-Y
Engine
control
relay
Oxygen sensor heater (rear) circuit
Battery
Wire colour code
B: Black LG: Light green G: Green L: Blue W: White Y: Yellow SB: Sky blue BR: Brown O: Orange GR: Gray
R: Red P: Pink V: Violet PU: Purple
AB
C-121
(MU803783)
6 <A-13> (*1) or
13 <C-31> (*2)
2
1
C-137
MU801446
NOTE
*1: L.H. drive vehicles
*2: R.H. drive vehicles
28
29
J/C (6)
C-105
4
3
To engine-ECU
TROUBLESHOOTING
MULTIPORT FUEL INJECTION (MPI)
13A-96
FUNCTION
• The power supply to the oxygen sensor heater
(rear) is controlled by the ON/OFF control of the
power transistor in the engine-ECU.
• Heating the oxygen sensor heater (rear) enables
the oxygen sensor to provide good response
even when the exhaust emission temperature is
low.
TROUBLE JUDGMENT
Check Conditions
• The engine coolant temperature is 20°C or
higher.
• The oxygen sensor heater (rear) is ON.
• The engine speed is 50 r/min. or more.
• A/C relay: OFF
• Radiator fan: OFF
• The system voltage is 11 − 16 V.
Judgment Criterion
• The heater current of oxygen sensor (rear) heater
0.2 A or less or 3.5 A or more for 4 seconds.
PROBABLE CAUSES
• Failed oxygen sensor heater (rear)
• Open/short circuit in oxygen sensor (rear) circuit
or loose connector contact
• Failed engine-ECU
DIAGNOSIS PROCEDURE
STEP 1. Connector check: C-137 oxygen sensor
(rear) connector
Q: Is the check result normal?
YES :
Go to Step 2 .
NO :
Repair or replace the connector.
STEP 2. Perform resistance measurement at
C-137 oxygen sensor (rear) connector.
• Disconnect connector, and measure at sensor
side.
• Resistance between terminal No. 3 and No. 4.
OK: 11
− 18 Ω
Q: Is the check result normal?
YES :
Go to Step 3 .
NO :
Replace the oxygen (rear) sensor.
STEP 3. Perform voltage measurement at C-137
oxygen sensor (rear) connector.
• Disconnect connector, and measure at harness
side.
• Ignition switch: "ON"
• Voltage between terminal No. 3 and earth.
OK: System voltage
Q: Is the check result normal?
YES :
Go to Step 5 .
NO :
Go to Step 4 .
AK305013
2 1
3
4
AB
Oxygen sensor(rear)
Connector : C-137
Harness side
connector
C-137
AK305013
2 1
3
4
AB
Oxygen sensor(rear)
Connector : C-137
Harness side
connector
C-137
AK305013
2 1
3
4
AB
Oxygen sensor(rear)
Connector : C-137
Harness side
connector
C-137
TROUBLESHOOTING
MULTIPORT FUEL INJECTION (MPI)
13A-97
STEP 4. Connector check: B-12X engine control
relay connector
Q: Is the check result normal?
YES :
Check intermediate connector C-105, and
repair if necessary. If intermediate
connector are normal, check and repair
harness between C-137 (terminal No. 3)
oxygen sensor (rear) connector and B-12X
(terminal No. 4) engine control relay
connector.
• Check power supply line for
open/short circuit.
NO :
Repair or replace the connector.
STEP 5. Perform voltage measurement at C-121
engine-ECU connector.
• Measure engine-ECU terminal voltage.
• Ignition switch: "ON"
• Voltage between terminal No. 26 and earth.
OK: System voltage
Q: Is the check result normal?
YES :
Go to Step 8 .
NO :
Go to Step 6 .
AK305003
2
1
3
4
AB
Connector : B-12X
B-12X
Harness side
connector
Relay box’s
triangle marks
AK305013
2 1
3
4
AB
Oxygen sensor(rear)
Connector : C-137
Harness side
connector
C-137
AK501995
2
3
4
5
6
7
8
9
11
12
13
14
15
16
17
18
19
20
30
21
22
23
24
25
26
27
28
29
31
32
33
34
35
1
10
AB
Connector: C-121
C-121 (GR)
C-121 (GR)
Harness side connector
<L. H. drive vehicles>
<R. H. drive vehicles>
TROUBLESHOOTING
MULTIPORT FUEL INJECTION (MPI)
13A-98
STEP 6. Connector check: C-121 engine-ECU
connector
Q: Is the check result normal?
YES :
Go to Step 7 .
NO :
Repair or replace the connector.
STEP 7. Check harness between C-137 (terminal
No. 4) oxygen sensor connector and C-121
(terminal No. 26) engine-ECU connector.
• Check earthing line for open/short circuit.
Q: Is the check result normal?
YES :
Replace the engine-ECU.
NO :
Repair the damaged harness wire.
AK501995
2
3
4
5
6
7
8
9
11
12
13
14
15
16
17
18
19
20
30
21
22
23
24
25
26
27
28
29
31
32
33
34
35
1
10
AB
Connector: C-121
C-121 (GR)
C-121 (GR)
Harness side connector
<L. H. drive vehicles>
<R. H. drive vehicles>
AK305013
2 1
3
4
AB
Oxygen sensor(rear)
Connector : C-137
Harness side
connector
C-137
AK501995
2
3
4
5
6
7
8
9
11
12
13
14
15
16
17
18
19
20
30
21
22
23
24
25
26
27
28
29
31
32
33
34
35
1
10
AB
Connector: C-121
C-121 (GR)
C-121 (GR)
Harness side connector
<L. H. drive vehicles>
<R. H. drive vehicles>
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