Mitsubishi Lancer Evolution X. Manual - part 380

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-585

DTC SET CONDITIONS

Logic Flow Chart

Check Condition

• Change of accelerator pedal position sensor 

(sub) output voltage per 40 milliseconds is lower 
than 0.06 volt.

• Range/performance error of accelerator pedal 

position sensor (main and sub) circuit is not 
detected.

Judgment Criterion

• Voltage obtained with the formula given below is 

0.4 volt or higher for 0.5 second: accelerator 
pedal position sensor (main) output voltage − 

accelerator pedal position sensor (sub) output 
voltage.

NOTE: The accelerator pedal position sensor volt-
age used for the judgement is converted into the 
accelerator pedal position sensor voltage for the 
internal processing by the ECM.

.

FAIL-SAFE AND BACKUP FUNCTION

• Throttle opening degree position is in default 

position.

.

OBD-II DRIVE CYCLE PATTERN

• None.

.

AK604353

Start

Yes

Yes

Yes

No

No

No

|APS (main) - APS (sub)| 

>= 0.4V

Continuous

failure for 0.5sec

Malfunction

End

Good

Monitoring
conditions

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-586

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

• Accelerator pedal position sensor failed.
• 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, read the diagnostic 
trouble code (DTC).

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) Read the DTC.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the diagnostic trouble code other than P1237 set?

YES : Refer to, Diagnostic Trouble Code Chart 

P.13A-48

. 

NO :  Go to Step 2. 

STEP 2. Using scan tool MB991958, check data list.
(1) Turn the ignition switch to the "ON" position.
(2) Check the following item in the data list. Refer to Data List 

Reference Table 

P.13A-818

.

a. Item 11: Accelerator pedal position sensor (main)
b. Item 12: Accelerator pedal position sensor (sub)

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

YES : Go to Step 3.
NO :  Repair or replace it. Then go to Step 4.

AC608435

Data link connector

MB991827

MB991824

MB991910

AB

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-587

STEP 3. 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 P1237 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 4.

NO :  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

.

STEP 4. Using scan tool MB991958, read the diagnostic 
trouble code (DTC).
(1) Turn the ignition switch to the "ON" position.
(2) Read the DTC.
(3) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is DTC P1237 set?

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

DTC P1238: Mass Airflow Sensor Plausibility (Torque Monitor)

.

TECHNICAL DESCRIPTION

Compare the actual measurement of volumetric effi-
ciency by a mass airflow sensor signal with volumet-
ric efficiency estimated from a throttle position 
sensor (main or sub) signal.

.

MONITOR EXECUTION

Continuous

.

MONITOR EXECUTION CONDITIONS 
(Other monitor and Sensor)

Other Monitor (There is no temporary DTC stored 

in memory for the item monitored below)

• Not applicable

Sensor (The sensor below is determined to be 

normal)

• Not applicable

.

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-588

DTC SET CONDITIONS

Check Conditions

• Engine speed is 750 r/min or higher.
• Except while fuel is being shut off.

Judgment Criterion

• For 0.9 second, the difference between the actual 

volumetric efficiency and the volumetric efficiency 
estimated by the throttle position sensor (main) is 
45 percent or more.

or

• For 0.9 second, the difference between the actual 

volumetric efficiency and the volumetric efficiency 
estimated by the throttle position sensor (sub) is 
45 percent or more.

.

FAIL-SAFE AND BACKUP FUNCTION

• Throttle opening degree position is in default 

position.

.

OBD-II DRIVE CYCLE PATTERN

Refer to Diagnostic Function − OBD-II Drive Cycle − 

Pattern 16 

P.13A-9

.

.

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

• Mass airflow sensor system failed.
• ECM failed.

AK604351

Start

Yes

Yes

Yes

No

No

No

Continuous failure

for specified time

Malfunction

End

Good

Monitoring
conditions

|Ec-calculated Ec| 
> specified value

Ec: load value