Mitsubishi Lancer Evolution X. Manual - part 387

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-613

DTC P1603: Battery Backup Circuit Malfunction

.

TECHNICAL DESCRIPTION

• The ECM checks the open circuit of battery 

backup line.

NOTE: When the system detects an open circuit in 
the battery backup line, it makes 1 failure judgment 
of other diagnostic trouble codes (DTCs).

.

AK604256

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

104

2

7.5A

AD

WHITE

WHITE

RED

B-10

36

FUSIBLE LINK

BATTERY BACKUP CIRCUIT

RELAY BOX
(ENGINE COMPARTMENT)

ENGINE
CONTROL
MODULE

BATTERY
BACKUP

AK704235 AB

Connector: B-10

ECM

B-10 (GR)

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

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MULTIPORT FUEL INJECTION (MFI)

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DESCRIPTIONS OF MONITOR METHODS

Battery backup line voltage is under specified value.

.

MONITOR EXECUTION

Continuous

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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

• Engine starting sequence was completed.
• Battery positive voltage is higher than 10 volts.

Judgement Criterion

• Battery backup line voltage has continued to be 6 

volts or lower for 2 seconds.

.

AK604357

Start

Yes

Yes

Yes

No

No

No

Continuous

failure for 2secs

Malfunction

End

Good

Monitoring
conditions

Circuit voltage

< 6V

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

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MULTIPORT FUEL INJECTION (MFI)

13A-615

FAIL-SAFE AND BACKUP FUNCTION

• All diagnosis codes are stored once failure judg-

ment is completed.

.

OBD-II DRIVE CYCLE PATTERN

• None.

.

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

• Open or shorted battery backup line, 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

• MB992110: Power Plant ECU Check 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) Erase the DTC.
(4) Start the engine and run it at idle.
(5) Read the DTC.
(6) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is DTC P1603 set?

YES : Go to Step 2.
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 2. Check harness connector B-10 at ECM 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 5.

AC608435

Data link connector

MB991827

MB991824

MB991910

AB

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

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MULTIPORT FUEL INJECTION (MFI)

13A-616

STEP 3. Measure the backup power supply voltage at ECM 
connector B-10 by using power plant ECU check harness 
special tool MB992110.
(1) Disconnect all ECM connectors. Connect the power plant 

ECU check harness special tool MB992110 between the 
separated connectors.

(2) Measure the voltage between terminal No. 104 and ground.

• Voltage should be battery positive voltage.

Q: Is battery positive voltage (approximately 12 volts) 

present?
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 5.

NO :  Go to Step 4.

STEP 4. Measure the backup power supply voltage at ECM 
harness side connector B-10.
(1) Disconnect the ECM connector B-10 and measure at the 

harness side.

(2) Measure the voltage between terminal No. 104 and ground.

• Voltage should be battery positive voltage.

Q: Is battery positive voltage (approximately 12 volts) 

present?
YES : Repair harness wire between battery and ECM 

connector B-10 (terminal No. 104) because of 
harness damage. Then go to Step 5.

NO :  Repair harness wire between battery and ECM 

connector B-10 (terminal No. 104) because of open 
circuit or short circuit to ground. Then go to Step 5.

AK604171

ECM

AB

Body side harness 

MB992110

AK604045

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94 93 92 91 90 89 88 87 86 85 84 83

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100

101

102

103

104

105

106

112

113

114

109 108

107

110

111

115

116

117

118

AC

Power plant ECU
check harness connector

AK604223

82 81 80 79 78 77 76 75 74 73 72 71

94 93 92 91 90 89 88 87 86 85 84 83

99 98 97 96 95

100

101

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103

104

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112

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114

109 108

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118

AD

B-10 harness
connector: component side