Mitsubishi Lancer Evolution X. Manual - part 395

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-645

TROUBLESHOOTING HINTS (The most 
likely causes for this code to be set are:)

• Accelerator pedal position sensor failed.

• Open accelerator pedal position sensor (main) 

circuit, harness damage or connector damage.

• ECM failed.

DIAGNOSIS

Required Special Tools:

• MB991958: Scan tool (M.U.T.-III Sub Assembly)

• MB991824: V.C.I.
• MB991827: USB Cable
• MB991910: Main Harness A

STEP 1. Using scan tool MB991958, check data list item 11: 
Accelerator Pedal Position Sensor (main).

CAUTION

To prevent damage to scan tool MB991958, always turn the 
ignition switch to the "LOCK" (OFF) position before con-
necting or disconnecting scan tool MB991958.
(1) Connect scan tool MB991958 to the data link connector.
(2) Turn the ignition switch to the "ON" position.
(3) Set scan tool MB991958 to the data reading mode for item 

11, Accelerator Pedal Position Sensor (main).

• Output voltage is between 0.9 and 1.1 volts when foot is 

released from accelerator pedal.

• Output voltage is 4.0 volts or higher when accelerator 

pedal is fully depressed.

(4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the sensor operating properly?

YES : It can be assumed that this malfunction is intermittent. 

Refer to GROUP 00, How to Use 
Troubleshooting/Inspection Service Points − How to 

Cope with Intermittent Malfunctions 

P.00-15

.

NO :  Go to Step 2.

STEP 2. Check harness connector C-01 at accelerator 
pedal position sensor for damage.
Q: Is the harness connector in good condition?

YES : Go to Step 3.
NO :  Repair or replace it. Refer to GROUP 00E, Harness 

Connector Inspection 

P.00E-2

. Then go to Step 8.

AC608435

Data link connector

MB991827

MB991824

MB991910

AB

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-646

STEP 3. Check the continuity at accelerator pedal position 
sensor harness side connector C-01.
(1) Disconnect the connector C-01 and measure at the harness 

side.

(2) Measure the continuity between terminal No. 2 and ground.

• Continuity (2 ohms or less)

Q: Does continuity exist?

YES : Go to Step 7.
NO :  Go to Step 4.

STEP 4. Check harness connector B-10 at ECM for 
damage.
Q: Is the harness connector in good condition?

YES : Go to Step 5.
NO :  Repair or replace it. Refer to GROUP 00E, Harness 

Connector Inspection 

P.00E-2

. Then go to Step 8.

STEP 5. Check for open circuit and harness damage 
between accelerator pedal position sensor connector C-01 
(terminal No. 2) and ECM connector B-10 (terminal No. 76).
Q: Is the harness wire in good condition?

YES : Go to Step 6.
NO :  Repair it. Then go to Step 8.

STEP 6. Using scan tool MB991958, check data list item 11: 
Accelerator Pedal Position Sensor (main).
(1) Turn the ignition switch to the "ON" position.
(2) Set scan tool MB991958 to the data reading mode for item 

11, Accelerator Pedal Position Sensor (main).

• Output voltage is between 0.9 and 1.1 volts when foot is 

released from accelerator pedal.

• Output voltage is 4.0 volts or higher when accelerator 

pedal is fully depressed.

(3) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the sensor operating properly?

YES : It can be assumed that this malfunction is intermittent. 

Refer to GROUP 00, How to Use 
Troubleshooting/Inspection Service Points − How to 

Cope with Intermittent Malfunctions 

P.00-15

.

NO :  Replace the ECM. When the ECM is replaced, 

register the ID code. Refer to GROUP 42B, ID Code 
Registration Necessity Judgment Table <Vehicles 
with KOS> 

P.42B-11

 or GROUP 42C, ID Codes 

Registration Judgment Table <Vehicles with WCM> 

P.42C-9

. Then go to Step 8.

AK704747

1

6 5 4 3 2

AB

C-01 harness
connector:
component side 

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-647

STEP 7. Replace the accelerator pedal position sensor.
(1) Replace the accelerator pedal position sensor.
(2) Turn the ignition switch to the "ON" position.
(3) After the DTC has been deleted, read the DTC again.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is DTC P2123 set?

YES : Replace the ECM. When the ECM is replaced, 

register the ID code. Refer to GROUP 42B, ID Code 
Registration Necessity Judgment Table <Vehicles 
with KOS> 

P.42B-11

 or GROUP 42C, ID Codes 

Registration Judgment Table <Vehicles with WCM> 

P.42C-9

. Then go to Step 8.

NO :  The inspection is complete.

STEP 8. Using scan tool MB991958, read the diagnostic 
trouble code (DTC).
(1) Turn the ignition switch to the "ON" position.
(2) After the DTC has been deleted, read the DTC again.
(3) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is DTC P2123 set?

YES : Retry the troubleshooting.
NO :  The inspection is complete.

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-648

DTC P2127: Accelerator Pedal Position Sensor (sub) Circuit Low Input

.

CIRCUIT OPERATION

• A 5-volt power supply is applied on the accelera-

tor pedal position sensor (sub) power terminal 
(terminal No. 4) from the ECM (terminal No. 78).

• A voltage that is according to the accelerator 

opening angle is sent to the ECM (terminal No. 
77) from the accelerator pedal position sensor 
(sub) output terminal (terminal No. 6).

• The ground terminal (terminal No. 5) is grounded 

with ECM (terminal No. 79).

.

AK604257

71 72 73 74 75 76 77 78 79 80 81 82

83 84 85 86 87 88 89 90 91 92 93 94

95 96 97 98 99

100 101 102 103 104

112 113 114

109

108

107

110 111

115 116

106

105

118

117

6

1 2 3 4 5

AH

5 V

78

4

YELLO

W

-RED

YELLO

W

-BLA

CK

BR

O

WN

77

79

6

5

B-10

C-01

HALL IC

ENGINE
CONTROL
MODULE

ACCELERATOR PEDAL POSITION SENSOR (SUB) CIRCUIT

ACCELERATOR PEDAL
POSITION SENSOR (SUB)

AK704235 AB

Connector: B-10

ECM

B-10 (GR)

AK704296

Accelerator pedal 
position sensor

Accelerator
pedal

AB

C-01 (B)

Connector: C-01