Mitsubishi Lancer Evolution X. Manual - part 378

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-577

DTC P1234: Throttle Position Sensor (Sub) Plausibility

.

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 (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

.

DTC SET CONDITIONS

Logic Flow Chart

Check Conditions

• The engine speed is between 750 and 3,000 

r/min. Or, the throttle position sensor (main) out-
put voltage is 3 volts or lower.

• Except while fuel is being shut off.

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

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-578

Judgment Criterion

• For 0.8 second, the difference between the actual 

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

.

FAIL-SAFE AND BACKUP FUNCTION

• Throttle opening degree is restricted.
• Throttle opening degree position is in default 

position if throttle position sensor (main) fails.

.

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:)

• Throttle position sensor (sub) system failed.
• Intake system vacuum leak.
• 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

• MB991658: Test Harness

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 P1234 set?

YES : Refer to, Diagnostic Trouble Code Chart 

P.13A-48

. 

NO :  Go to Step 2. 

AC608435

Data link connector

MB991827

MB991824

MB991910

AB

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-579

STEP 2. Using scan tool MB991958, check data list item 15: 
Throttle Position Sensor (sub).
(1) Turn the ignition switch to the "ON" position.
(2) Detach the intake air hose at the throttle body.
(3) Disconnect the connector of the throttle position sensor.
(4) Use test harness special tool (MB991658) to connect only 

terminals No. 3, No. 4, No. 5, and No. 6.

(5) Set scan tool MB991958 to the data reading mode for item 

15, Throttle Position Sensor (sub).

• Output voltage should be 4.0 volts or more when the 

throttle valve is fully closed with your finger.

• Output voltage should be 1.0 volt or less when the throt-

tle valve is fully open with your finger.

(6) 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 3.

STEP 3. Check for intake system vacuum leak.
Q: Are there any abnormalities?

YES : Repair it. Then go to Step 5.
NO :  Go to Step 4.

STEP 4. Check the trouble symptoms.
(1) Carry out a test drive with the drive cycle pattern. Refer to 

Diagnostic Function − OBD-II Drive Cycle − Pattern 16 

P.13A-9

.

(2) Check the diagnostic trouble code (DTC).
Q: Is DTC P1234 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

. The go to Step 5.

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 5. Test the OBD-II drive cycle.
(1) Carry out a test drive with the drive cycle pattern. Refer to 

Diagnostic Function − OBD-II Drive Cycle − Pattern 16 

P.13A-9

.

(2) Check the diagnostic trouble code (DTC).
Q: Is DTC P1234 set?

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

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-580

DTC P1235: Mass Airflow Sensor Plausibility

.

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

.

DTC SET CONDITIONS

Logic Flow Chart

Check Conditions

• The plausibility error of the throttle position sen-

sor (main) is detected.

• The plausibility error of the throttle position sen-

sor (sub) is detected.

AK801295

Start

Yes

Yes

Yes

No

No

No

Continuous failure

for 0.76sec

Malfunction

End

Good

Monitoring
conditions

|Calculated Ec {TPS (main)}

-calculated Ec {TPS (sub)}| 

< 8.8 percent

Ec: load value