Nissan Frontier. Manual — part 420
P0300, P0301, P0302, P0303, P0304 MISFIRE
EC-251
< DTC/CIRCUIT DIAGNOSIS >
[QR25DE]
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When disconnecting each fuel injector harness connector one at a
time, is there any cylinder which does not produce a momentary
engine speed drop?
Yes or No
Yes
>> GO TO 4.
No
>> GO TO 9.
4.
CHECK FUNCTION OF FUEL INJECTOR
Does each fuel injector make an operating sound at idle?
Yes or No
Yes
>> GO TO 5.
No
>> Check fuel injector(s) and circuit(s).
5.
CHECK FUNCTION OF IGNITION COIL-I
CAUTION:
Never the following procedure in a place with no combusyible objects and good ventilation.
1. Turn ignition switch OFF.
2. Remove fuel pump fuse in IPDM E/R to release fuel pressure.
NOTE:
Do not use CONSULT to release fuel pressure, or fuel pressure
applies again during the following procedure.
3. Start engine.
4. After engine stalls, crank it two or three times to release all fuel
pressure.
5. Turn ignition switch OFF.
6. Remove all ignition coil harness connectors to avoid the electri-
cal discharge from the ignition coils.
7. Remove ignition coil and spark plug of the cylinder to be
checked.
8. Crank engine for 5 seconds or more to remove combustion gas in the cylinder.
9. Connect spark plug and harness connector to ignition coil.
10. Fix ignition coil using a rope etc. with gap of 13 - 17 mm
between the edge of the spark plug and grounded metal portion
as shown in the figure.
11. Crank engine for about three seconds, and check whether spark
is generated between the spark plug and the grounded metal
portion.
CAUTION:
BBIA0604E
PBIB1986E
Spark should be generated.
BBIA0534E
PBIB2325E
EC-252
< DTC/CIRCUIT DIAGNOSIS >
[QR25DE]
P0300, P0301, P0302, P0303, P0304 MISFIRE
• Never place the spark plug and the ignition coil within 50 cm (19.7 in) each other. Be careful not
to get an electrical shock while checking, because the electrical discharge voltage becomes 20
kV or more.
• It might damage the ignition coil if the gap of more than 17 mm is made.
NOTE:
When the gap is less than 13 mm, a spark might be generated even if the coil is malfunctioning.
OK or NG
OK
>> GO TO 9.
NG
>> GO TO 6.
6.
CHECK FUNCTION OF IGNITION COIL-II
1. Turn ignition switch OFF.
2. Disconnect spark plug and connect a non-malfunctioning spark plug.
3. Crank engine for about 3 seconds, and recheck whether spark is generated between the spark plug and
the grounded metal portion.
OK or NG
OK
>> GO TO 7.
NG
>> Check ignition coil, power transistor and their circuits.
7.
CHECK SPARK PLUG
Check the initial spark plug for fouling, etc.
OK or NG
OK
>> Replace spark plug(s) with standard type one(s). Refer
to
EM-36, "Removal and Installation"
NG
>> 1. Repair or clean spark plug.
2. GO TO 8.
8.
CHECK FUNCTION OF IGNITION COIL-III
1. Reconnect the initial spark plugs.
2. Crank engine for about 3 seconds, and recheck whether spark is generated between the spark plug and
the grounded portion.
OK or NG
OK
>> INSPECTION END
NG
>> Replace spark plug(s) with standard type one(s). For spark plug type. Refer to
.
9.
CHECK COMPRESSION PRESSURE
Check compression pressure.
.
OK or NG
OK
>> GO TO 10.
NG
>> Check pistons, piston rings, valves, valve seats and cylinder head gaskets.
10.
CHECK FUEL PRESSURE
1. Install all removed parts.
2. Release fuel pressure to zero. Refer to
3. Install fuel pressure gauge kit [SST (J-44321)] and check fuel pressure. Refer to
.
Spark should be generated.
SEF156I
Spark should be generated.
P0300, P0301, P0302, P0303, P0304 MISFIRE
EC-253
< DTC/CIRCUIT DIAGNOSIS >
[QR25DE]
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OK or NG
OK
>> GO TO 12.
NG
>> GO TO 11.
11.
DETECT MALFUNCTIONING PART
Check the following.
• Fuel pump and circuit.
• Fuel pressure regulator (Refer to
• Fuel lines
• Fuel filter for clogging
>> Repair or replace.
12.
CHECK IGNITION TIMING
Check the following items. Refer to
.
OK or NG
OK
>> GO TO 13.
NG
>> Follow the
.
13.
CHECK A/F SENSOR 1 INPUT SIGNAL CIRCUIT
1. Turn ignition switch OFF.
2. Disconnect ECM harness connector and A/F sensor 1 harness
connector.
3. Check harness continuity between the following terminals. Refer
to Wiring Diagram.
4. Check harness continuity between ECM terminals 45, 49 or A/F sensor 1 terminals 1, 2 and ground. Refer
to Wiring Diagram.
5. Also check harness for short to power.
OK or NG
OK
>> GO TO 14.
NG
>> Repair open circuit, short to ground or short to power in harness or connectors.
14.
CHECK A/F SENSOR 1 HEATER
EC-157, "Component Inspection"
OK or NG
OK
>> GO TO 15.
NG
>> Replace A/F sensor 1. Refer to
At idle: Approximately 350 kPa (3.57 kg/cm
2
, 51 psi)
Items
Specifications
Target idle speed
A/T: 700
± 50 rpm (in P or N position)
M/T: 625
± 50 rpm (in Neutral position)
Ignition timing
A/T: 15
± 5° BTDC (in P or N position)
M/T: 15
± 5° BTDC (in Neutral position)
A/F sensor 1 terminal
ECM terminal
1
45
2
49
Continuity should exist.
Continuity should not exist.
BBIA0617E
EC-254
< DTC/CIRCUIT DIAGNOSIS >
[QR25DE]
P0300, P0301, P0302, P0303, P0304 MISFIRE
15.
CHECK MASS AIR FLOW SENSOR
With CONSULT
Check “MASS AIR FLOW” in “DATA MONITOR” mode with CONSULT.
With GST
Check mass air flow sensor signal in SERVICE $01 with GST.
OK or NG
OK
>> GO TO 16.
NG
>> Check connectors for rusted terminals or loose connections in the mass air flow sensor circuit or
grounds.Refer to
16.
CHECK SYMPTOM MATRIX CHART
Check items on the rough idle symptom in
EC-461, "Symptom Matrix Chart"
.
OK or NG
OK
>> GO TO 17.
NG
>> Repair or replace.
17.
ERASE THE 1ST TRIP DTC
Some tests may cause a 1st trip DTC to be set.
Erase the 1st trip DTC from the ECM memory after performing the tests. Refer to
>> GO TO 18.
18.
CHECK INTERMITTENT INCIDENT
Perform
GI-42, "Intermittent Incident"
.
>> INSPECTION END
At idling
: 1.0 - 4.0 g/s
At 2,500 rpm
: 4.0 - 12.0 g/s
At idling
: 1.0 - 4.0 g/s
At 2,500 rpm
: 4.0 - 12.0 g/s
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