Nissan Frontier. Manual — part 393
TROUBLE DIAGNOSIS - SPECIFICATION VALUE
EC-143
< DTC/CIRCUIT DIAGNOSIS >
[QR25DE]
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1. Start engine.
2. Select “A/F ALPHA-B1” in “DATA MONITOR (SPEC)” mode, and make sure that indication is within the
SP value.
OK or NG
OK
>> INSPECTION END
NG
>> GO TO 15.
15.
DISCONNECT AND RECONNECT ECM HARNESS CONNECTOR
1. Stop the engine.
2. Disconnect ECM harness connector. Check pin terminal and connector for damage, and then reconnect it.
>> GO TO 16.
16.
CHECK “A/F ALPHA-B1”
1. Start engine.
2. Select “A/F ALPHA-B1” in “DATA MONITOR (SPEC)” mode, and make sure that each indication is within
the SP value.
OK or NG
OK
>> INSPECTION END
NG
>> Detect malfunctioning part according to
EC-461, "Symptom Matrix Chart"
17.
CHECK “B/FUEL SCHDL”
Select “B/FUEL SCHDL” in “DATA MONITOR (SPEC)” mode, and make sure that indication is within the SP
value.
OK or NG
OK
>> INSPECTION END
NG (More than the SP value)>>GO TO 18.
NG (Less than the SP value)>>GO TO 25.
18.
DETECT MALFUNCTIONING PART
1. Check for the cause of large engine friction. Refer to the following.
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Engine oil level is too high
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Engine oil viscosity
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Belt tension of power steering, alternator, A/C compressor, etc. is excessive
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Noise from engine
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Noise from transmission, etc.
2. Check for the cause of insufficient combustion. Refer to the following.
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Valve clearance malfunction
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Intake valve timing control function malfunction
-
Camshaft sprocket installation malfunction, etc.
>> Repair or replace malfunctioning part, and then GO TO 30.
19.
CHECK INTAKE SYSTEM
Check for the cause of uneven air flow through mass air flow sensor. Refer to the following.
• Crushed air ducts
• Malfunctioning seal of air cleaner element
• Uneven dirt of air cleaner element
• Improper specification of intake air system
OK or NG
OK
>> GO TO 21.
NG
>> Repair or replace malfunctioning part, and then GO TO 20.
20.
CHECK “A/F ALPHA-B1” AND “B/FUEL SCHDL”
Select “A/F ALPHA-B1” and “B/FUEL SCHDL” in “DATA MONITOR (SPEC)” mode, and make sure that each
indication is within the SP value.
OK or NG
OK
>> INSPECTION END
EC-144
< DTC/CIRCUIT DIAGNOSIS >
[QR25DE]
TROUBLE DIAGNOSIS - SPECIFICATION VALUE
NG (“B/FUEL SCHDL” is more, “A/F ALPHA-B1” is less than the SP value)>>GO TO 21.
21.
DISCONNECT AND RECONNECT MASS AIR FLOW SENSOR HARNESS CONNECTOR
1. Stop the engine.
2. Disconnect mass air flow sensor harness connector. Check pin terminal and connector for damage and
then reconnect it again.
>> GO TO 22.
22.
CHECK “A/F ALPHA-B1”
1. Start engine.
2. Select “A/F ALPHA-B1” in “DATA MONITOR (SPEC)” mode, and make sure that each indication is within
the SP value.
OK or NG
OK
>> 1. Detect malfunctioning part of mass air flow sensor circuit and repair it. Refer to
2. GO TO 29.
NG
>> GO TO 23.
23.
CHECK “MAS A/F SE-B1”
Select “MAS A/F SE-B1” in “DATA MONITOR (SPEC)” mode, and make sure that the indication is within the
SP value.
OK or NG
OK
>> GO TO 24.
NG (More than the SP value)>>Replace mass air flow sensor, and then GO TO 29.
24.
REPLACE ECM
CAUTION:
Perform PROCEDURE AFTER REPLACING ECM. Refer to
EC-121, "Procedure After Replacing ECM"
.
Replace ECM.
>> GO TO 29.
25.
CHECK INTAKE SYSTEM
Check for the cause of uneven air flow through mass air flow sensor. Refer to the following.
• Crushed air ducts
• Malfunctioning seal in air cleaner element
• Uneven dirt in air cleaner element
• Improper specification in intake air system
OK or NG
OK
>> GO TO 27.
NG
>> Repair or replace malfunctioning part, and then GO TO 26.
26.
CHECK “B/FUEL SCHDL”
Select “B/FUEL SCHDL” in “DATA MONITOR (SPEC)” mode, and make sure that indication is within the SP
value.
OK or NG
OK
>> INSPECTION END
NG (Less than the SP value)>>GO TO 27.
27.
CHECK “MAS A/F SE-B1”
Select “MAS A/F SE-B1” in “DATA MONITOR (SPEC)” mode, and make sure that indication is within the SP
value.
OK or NG
OK
>> GO TO 28.
NG (Less than the SP value)>>Replace mass air flow sensor, and then GO TO 30.
28.
CHECK INTAKE SYSTEM
Check for the cause of air leak after the mass air flow sensor. Refer to the following.
TROUBLE DIAGNOSIS - SPECIFICATION VALUE
EC-145
< DTC/CIRCUIT DIAGNOSIS >
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• Disconnection, looseness, and cracks in air duct
• Looseness of oil filler cap
• Disconnection of oil level gauge
• Open stuck, breakage, hose disconnection, or cracks in PCV valve
• Disconnection or cracks in EVAP purge hose, stuck open of EVAP canister purge volume control solenoid
valve
• Malfunctioning seal of rocker cover gasket
• Disconnection, looseness, or cracks in hoses, such as a vacuum hose, connecting to intake air system parts
• Malfunctioning seal in intake air system, etc.
>> GO TO 30.
29.
CHECK “A/F ALPHA-B1” AND “B/FUEL SCHDL”
Select “A/F ALPHA-B1” and “B/FUEL SCHDL” in “DATA MONITOR (SPEC)” mode, and make sure that each
indication is within the SP value.
OK or NG
OK
>> INSPECTION END
NG
>> Detect malfunctioning part according to
EC-461, "Symptom Matrix Chart"
30.
CHECK “B/FUEL SCHDL”
Select “B/FUEL SCHDL” in “DATA MONITOR (SPEC)” mode, and then make sure that indication is within the
SP value.
OK or NG
OK
>> INSPECTION END
NG
>> Detect malfunctioning part according to
EC-146
< DTC/CIRCUIT DIAGNOSIS >
[QR25DE]
POWER SUPPLY AND GROUND CIRCUIT
POWER SUPPLY AND GROUND CIRCUIT
Diagnosis Procedure
INFOID:0000000009480772
1.
INSPECTION START
Start engine.
Is engine running?
Yes or No
Yes
>> GO TO 8.
No
>> GO TO 2.
2.
CHECK ECM POWER SUPPLY CIRCUIT-I
1. Turn ignition switch OFF and then ON.
2. Check voltage between ECM terminal 93 and ground with CONSULT or tester.
OK or NG
OK
>> GO TO 4.
NG
>> GO TO 3.
3.
DETECT MALFUNCTIONING PART
Check the following.
• Fuse block (J/B) connector M4
• 10A fuse (No.1)
• Harness connectors M31, E152
• Harness for open or short between ECM and fuse
>> Repair open circuit, short to ground or short to power in harness or connectors.
4.
CHECK GROUND CONNECTIONS
1. Turn ignition switch OFF.
2. Loosen and retighten two ground screws on the body. Refer to
.
OK or NG
OK
>> GO TO 5.
NG
>> Repair or replace ground connections.
5.
CHECK ECM GROUND CIRCUIT FOR OPEN AND SHORT-I
1. Disconnect ECM harness connector.
2. Check harness continuity between ECM terminals 12, 16, 107, 108, 111, 112 and ground.
Refer to Wiring Diagram.
3. Also check harness for short to power.
OK or NG
OK
>> GO TO 7.
NG
>> GO TO 6.
Voltage: Battery voltage
BBIA0614E
Continuity should exist.
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