Diagnostic Procedure

WARNING: This page is about a different car, the 2005 Infiniti QX56. However, it is still accessible from the selected car via links, so may be relevant.

CHECK FOR INTAKE AIR LEAK AND PCV HOSE
1. Start engine and run it at idle speed.
2. Listen for the sound of the intake air leak.
3. Check PCV hose connection.
OK or NG
1. OK: GO TO 2.
2. NG: Discover air leak location and repair.
CHECK FOR EXHAUST SYSTEM CLOGGING
Stop engine and visually check exhaust tube, three way catalyst and muffler for dents.

OK or NG
1. OK: GO TO 3.
2. NG: Repair or replace it.
PERFORM POWER BALANCE TEST
With CONSULT-II
1. Perform "POWER BALANCE" in "ACTIVE TEST" mode.
2. Is there any cylinder which does not produce a momentary engine speed drop?
  
  Fig 1: CONSULT-II Display - "POWER BALANCE" In "ACTIVE TEST" Mode
  Courtesy of NISSAN MOTOR CO., U.S.A.
Without CONSULT-II

When disconnecting each injector harness connector one at a time, is there any cylinder which does not produce a momentary engine speed drop?

Fig 2: Locating Injector Harness Connectors
Courtesy of NISSAN MOTOR CO., U.S.A.

Yes or No
1. Yes: GO TO 4.
2. No: GO TO 7.
CHECK INJECTOR
Does each injector make an operating sound at idle?

Yes or No
1. Yes: GO TO 5.
2. No: Check injector(s) and circuit(s). Refer to "INJECTOR CIRCUIT ".
Fig 3: Listening To Each Injector Operating Sound
Courtesy of NISSAN MOTOR CO., U.S.A.
CHECK FUNCTION OF IGNITION COIL-1
CAUTION: Do the following procedure in the place where ventilation is good without the combustible.
1. Turn ignition switch OFF.
2. Remove fuel pump fuse in IPDM E/R to release fuel pressure.
  NOTE: Do not use CONSULT-II 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 electrical discharge from the ignition coils.
  
  Fig 4: Removing Fuel Pump Fuse In IPDM E/R To Release Fuel Pressure
  Courtesy of NISSAN MOTOR CO., U.S.A.
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 3 seconds, and check whether spark is generated between the spark plug and the grounded metal portion.
  1. Spark should be generated.
  CAUTION:
  - Do not approach to the spark plug and the ignition coil within 50cm. Be careful not to get an electrical shock while checking, because the electrical discharge voltage becomes 20kV or more.
    
    Fig 5: Checking Ignition Spark
    Courtesy of NISSAN MOTOR CO., U.S.A.
  - It might cause to damage the ignition coil if the gap of more than 17 mm is taken.
  NOTE: When the gap is less than 13 mm, the spark might be generated even if the coil is malfunctioning.
OK or NG
1. OK: GO TO 9.
2. NG: GO TO 6.
CHECK FUNCTION OF IGNITION COIL-II
1. Turn ignition switch OFF.
2. Disconnect spark plug and connect a known-good spark plug.
3. Crank engine for about 3 seconds, and recheck whether spark is generated between the spark plug and the grounded metal portion.
  1. Spark should be generated.
OK or NG
1. OK: GO TO 7.
2. NG: Check ignition coil, power transistor and their circuits. Refer to "IGNITION SIGNAL ".
CHECK SPARK PLUG
Check the initial spark plug for fouling, etc.

OK or NG
1. OK: Replace spark plug(s) with standard type one(s). For spark plug type, Refer to "SPARK PLUG (PLATINUM-TIPPED TYPE) ".
2. NG:
  1. Repair or clean spark plug.
  2. GO TO 8.
Fig 6: Checking Initial Spark Plug For Fouling
Courtesy of NISSAN MOTOR CO., U.S.A.
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.
  1. Spark should be generated.
OK or NG
1. OK: INSPECTION END
2. NG: Replace spark plug(s) with standard type one(s). For spark plug type, Refer to "CHANGING SPARK PLUGS ".
CHECK COMPRESSION PRESSURE
Check compression pressure. Refer to "CHECKING COMPRESSION PRESSURE ".
1. Standard: 1,275 kPa (13.0 kg/cm ² , 185 psi)/300 RPM
2. Minimum: 981 kPa (10.0 kg/cm ² , 142 psi)/300 RPM
3. Difference between each cylinder: 98 kPa (1.0 kg/cm ² , 14 psi)/300 RPM
OK or NG
1. OK: GO TO 10.
2. NG: Check pistons, piston rings, valves, valve seats and cylinder head gaskets.
CHECK FUEL PRESSURE
1. Install all removed parts.
2. Release fuel pressure to zero. Refer to "FUEL PRESSURE RELEASE ".
3. Install fuel pressure gauge and check fuel pressure. Refer to "FUEL PRESSURE CHECK ".
  1. At idle: Approximately 350 kPa (3.57 kg/cm ² , 51 psi)
OK or NG
1. OK: GO TO 12.
2. NG: GO TO 11.
DETECT MALFUNCTIONING PART
Check the following.
- Fuel pump and circuit (Refer to "FUEL PUMP CIRCUIT ".)
- Fuel pressure regulator (Refer to "FUEL PRESSURE CHECK ".)
- Fuel lines
- Fuel filter for clogging
  1. Repair or replace.

CHECK IGNITION TIMING

Check the following items. Refer to "BASIC INSPECTION ".

IGNITION TIMING SPECIFICATION

Items	Specifications
Target idle speed	650 +/-> 50 RPM (in P or N position)
Ignition timing	15 +/- 5+/- BTDC (in P or N position)

OK or NG

OK: GO TO 13.
NG: Follow the "BASIC INSPECTION ".

CHECK A/F SENSOR 1 INPUT SIGNAL
1. Turn ignition switch OFF.
2. Disconnect A/F sensor 1 harness connector.
  
  Fig 7: Checking A/F Sensor 1 Input Signal
  Courtesy of NISSAN MOTOR CO., U.S.A.
3. Disconnect ECM harness connector.
4. Check harness continuity between the following terminals. Refer to WIRING DIAGRAM .
  
  Fig 8: Terminals For Checking Harness Continuity
  Courtesy of NISSAN MOTOR CO., U.S.A.
  1. Continuity should exist.
5. Check harness continuity between the following terminals and ground. Refer to WIRING DIAGRAM .
  
  Fig 9: Terminals For Checking Harness Continuity
  Courtesy of NISSAN MOTOR CO., U.S.A.
  1. Continuity should not exist.
6. Also check harness for short to power.
OK or NG
1. OK: GO TO 14.
2. NG: Repair open circuit or short to ground or short to power in harness or connectors.
CHECK A/F SENSOR 1 HEATER
Refer to "COMPONENT INSPECTION ".

OK or NG
1. OK: GO TO 15.
2. NG: Replace (malfunctioning) A/F sensor 1.
CHECK MASS AIR FLOW SENSOR
Check mass air flow sensor signal in "DATA MONITOR" mode with CONSULT-II.
1. 3.0 - 9.0 g.m/sec: at idling
2. 9.0 - 28.0 g.m/sec: at 2,500 RPM
With GST

Check mass air flow sensor signal in Service $01 with GST.
1. 3.0 - 9.0 g.m/sec: at idling
2. 9.0 - 28.0 g.m/sec: at 2,500 RPM
OK or NG
1. OK: GO TO 16.
2. NG: Check connectors for rusted terminals or loose connections in the mass air flow sensor circuit or ground. Refer to "DTC P0101 MAF SENSOR ".
CHECK SYMPTOM MATRIX CHART
Check items on the rough idle symptom in "SYMPTOM MATRIX CHART ".

OK or NG
1. OK: GO TO 17.
2. NG: Repair or replace.
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 "HOW TO ERASE EMISSION-RELATED DIAGNOSTIC INFORMATION ".
1. OK: GO TO 18.
CHECK INTERMITTENT INCIDENT
Refer to "TROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENT ".
1. : INSPECTION END