Section 584 (Engine Control System - Component Testing (VQ40DE)): Precaution: Precautions: Precaution

WARNING: This page is about a different car, the 2012 Nissan Pathfinder. However, it is still accessible from the selected car via links, so may be relevant.

Always use a 12 volt battery as power source .
Never attempt to disconnect battery cables while engine is running .
Before connecting or disconnecting the ECM harness connector, turn ignition switch OFF and disconnect negative battery cable. Failure to do so may damage the ECM because battery voltage is applied to ECM even if ignition switch is turned OFF .
Before removing parts, turn ignition switch OFF and then disconnect negative battery cable .

Fig 1: Disconnecting Battery Negative Terminal
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Never disassemble ECM .
If a battery cable is disconnected, the memory will return to the ECM value .
The ECM will now start to self-control at its initial value. Engine operation can vary slightly when the terminal is disconnected. However, this is not an indication of a malfunction. Never replace parts because of a slight variation .
If the battery is disconnected, the following emission-related diagnostic information will be lost within 24 hours .

Diagnostic trouble codes
1st trip diagnostic trouble codes
Freeze frame data
1st trip freeze frame data
System readiness test (SRT) codes
Test values
<Flexible Fuel Vehicle>
Presumed ethanol mixture ratio

When connecting ECM harness connector, fasten it securely with levers as far as they will go as shown in the figure .

Fig 2: Fastening ECM Protector Lever
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When connecting or disconnecting pin connectors into or from ECM, take care not to damage pin terminals (bends or break) .
Check that there are not any bends or breaks on ECM pin terminal, when connecting pin connectors .
Securely connect ECM harness connectors .
A poor connection can cause an extremely high (surge) voltage to develop in coil and condenser, thus resulting in damage to ICs .
Keep engine control system harness at least 10 cm (4 in) away from adjacent harness, to prevent engine control system malfunctions due to receiving external noise, degraded operation of ICs, etc .

Fig 3: Identifying Bend And Break Pin Connector
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Keep engine control system parts and harness dry .
Before replacing ECM, perform "ECM Terminals and Reference Value" inspection and make sure ECM functions properly. Refer to "ECM TERMINAL AND REFERENCE VALUE ".
Handle mass air flow sensor carefully to avoid damage .
Never clean mass air flow sensor with any type of detergent .
Never disassemble electric throttle control actuator .
Even a slight leak in the air intake system can cause serious incidents .
Never shock or jar the camshaft position sensor (PHASE), crankshaft position sensor (POS) .

Fig 4: Precaution Before Replacing Transfer Control Unit
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After performing each TROUBLE DIAGNOSIS, perform DTC Confirmation Procedure or Overall Function Check .
The DTC should not be displayed in the DTC Confirmation Procedure if the repair is completed. The Overall Function Check should be a good result if the repair is completed .

Fig 5: Identifying Malfunction Indicator Lamp
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When measuring ECM signals with a circuit tester, never allow the two tester probes to contact .
Accidental contact of probes will cause a short circuit and damage the ECM power transistor .

Fig 6: Checking Harness Connector For Solenoid Valve Using Circuit Tester
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B1 indicates bank 1, B2 indicates bank 2 as shown in the figure .

Fig 7: Identifying Cylinder Number And Bank Layout
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Never operate fuel pump when there is no fuel in lines .
Tighten fuel hose clamps to the specified torque .

Fig 8: Identifying Fuel Level Sensor Unit And Fuel Pressure Regulator
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Never depress accelerator pedal when starting .
Immediately after starting, Never rev up engine unnecessarily .
Never rev up engine just prior to shutdown .

Fig 9: Caution Do Not Depress Accelerator Pedal When Starting
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When installing C.B. ham radio or a mobile phone, Always observe the following as it may adversely affect electronic control systems depending on installation location .

Keep the antenna as far as possible from the electronic control units .
Keep the antenna feeder line more than 20 cm (8 in) away from the harness of electronic controls .
Never let them run parallel for a long distance .
Adjust the antenna and feeder line so that the standing-wave radio can be kept smaller .

Fig 10: Identifying C.B. Ham Radio
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Always ground the radio to vehicle body .

Fig 11: Fastening ECM Protector Lever

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