Description

Infiniti G35 2004 Diagnostics Manual

Pulling a DTC on a 2004 Infiniti G35 and getting a generic code description from a parts-store printout isn’t diagnosis – it’s a gamble. The ECM can throw a P0300 that means five different things, and without the factory diagnostic procedure you’re wasting hours swapping parts. This 648-page Infiniti G35 2004 Diagnostics Manual is the same binder the dealer techs use. It tells you exactly which sensor to test, what resistance range to expect, and how to interpret freeze frame data. No aftermarket shortcut – just the OEM logic.

For a home mechanic or a shop owner, the difference between a paid job and a comeback is whether you can confirm a repair by the book. The manual gives you the step sequence: start with Basic Inspection, move through the Symptom Matrix Chart, then check the DTC index. Page references are built into the procedures so you don’t flip blind. The wiring diagrams are sectioned by system – engine, SRS, OBD – so you isolate circuits without pulling the wrong harness.

I’ve been wrenching for 28 years, and I’ve watched guys burn three hours chasing a ground fault that the factory flow chart would have nailed in twenty minutes. That’s what this Diagnostic Manual prevents.

Diagnostic Code Index and DTC No. Index

The INDEX FOR DTC section breaks codes two ways: alphabetical by symptom name, and numeric by DTC number. If you have a P1130, the DTC No. Index sends you directly to the trouble diagnosis page that covers the HO2S circuit. No need to thumb through every system description. The alphabetical index is useful when you only know the symptom – “rough idle”, “hesitation” – and need the associated DTC list. For a 2004 Infiniti G35, the factory index is the fastest path to the right diagnostic routine.

Precautions for SRS, Battery, and OBD System

Before you touch anything on the G35, the manual opens with PRECAUTIONS. That includes the SRS “AIR BAG” and “SEAT BELT PRE-TENSIONER” disabling procedure. If you ignore the steps and pop an airbag, you’re looking at a $1200 module replacement and possible injury. It also covers battery service – terminal disconnection order – and the OBD system of engine and A/T. The wiring diagrams and trouble diagnosis section on page 19 gives a base rule: never probe a connector with a test light unless the manual says you can. Sensitive circuits on the CAN bus can be shorted by a careless back-probe.

These precautions aren’t boilerplate – they’re specific to the 2004 Infiniti G35 and the way the Nissan electrical architecture works.

Engine Control System – MFI, EI, CAN Communication

The ENGINE CONTROL SYSTEM chapter covers the Multiport Fuel Injection (MFI) and Electronic Ignition (EI) systems. It includes input/output signal charts, closed-loop mixture control, and the self-learning logic. The CAN communication section explains how the ECM talks to the TCM and BCM, and distinguishes M/T and A/T models. If you have a no-start or a drivability issue that points to fuel or spark, this chapter gives you the system description first, then the diagnostic procedure. That order matters – understanding the intended function helps you recognize an abnormal reading.

For example, the MFI system’s MIXTURE RATIO SELF-LEARNING CONTROL adjusts long-term fuel trim. If the self-learning value is maxed out, you don’t replace the oxygen sensor – you look for a vacuum leak or fuel pressure issue. The manual tells you that on page 25.

Basic Service Procedure – Idle Speed, Ignition Timing, Fuel Pressure

The BASIC SERVICE PROCEDURE section is where you set idle speed, adjust ignition timing, and check fuel pressure. It lists the required tools: a CONSULT-II or GST, a tachometer, a timing light, and a fuel pressure gauge with the Nissan adapter. The procedure for Idle Air Volume Learning is critical after a throttle body cleaning or ECM replacement – and the manual gives both the CONSULT-II and the non-CONSULT-II method. Without this, the G35 will idle high or stall on deceleration.

Fuel pressure release steps are included, with a warning about residual pressure in the line. Test pressure spec is given on page 48. Use the factory spec – aftermarket manuals often skip the exact pressure range for the 2004 VQ35DE.

On Board Diagnostic (OBD) System – Two Trip Logic, MIL, SRT Codes

The ON BOARD DIAGNOSTIC (OBD) SYSTEM chapter explains the two-trip detection logic, how the Malfunction Indicator Lamp (MIL) operates, and how to read System Readiness Test (SRT) codes. The G35 uses a specific drive pattern to set SRT codes – the manual spells out the speed and load conditions. If you’re prepping for an emissions inspection, you can use this section to confirm all monitors are complete without driving 50 miles randomly. It also covers the IVIS (Infiniti Vehicle Immobilizer System – NATS) and how to clear DTCs without wiping learned adaptations.

For a $20 access that saves you a smog failure, this chapter pays for itself.

Why OEM Factory Documentation Matters

Aftermarket diagnostics manuals are written by editors who reverse-engineer the repair sequence. They often merge wiring diagrams from different model years, mislabel connector views, or omit the specific test values that the Infiniti ECM expects. This manual is the original factory document — scanned from the same PDF the dealer network uses. Every DTC index entry, every torque spec (where applicable), every SRS precaution is verbatim from Nissan. No guesswork, no third-party interpretation. If you’re serious about repairing a 2004 G35, this is the source.

Does this manual cover the fuel injection system?

The MFI system is detailed on pages 25-27 with input/output signal charts, closed-loop feedback, and fuel shut-off logic. Yes, it covers the entire fuel injection circuit.

What about wiring diagrams – are they complete?

The manual includes wiring diagrams and trouble diagnosis in the PRECAUTIONS section on page 19. However, the ENGINE CONTROL SYSTEM chapter contains system diagrams for the ECM, sensors, and actuators. If you need body wiring, check the related Body, Lock & Security System manual.

Can I use this for the 2003 G35?

This manual is for the 2004 model year. The 2003 G35 has a similar engine control system, but component locations and connector pinouts changed slightly. For a 2003, look at the Infiniti G35 Coupe 2006 Service Manual or the Infiniti G35 2003 Automatic Transmission Service Manual for transmission-specific diagnostics.

Does it include torque specs for engine components?

This is a diagnostics manual – it focuses on electrical and electronic diagnostics. Torque values for mechanical components like cylinder head bolts are in the service repair manual. For body and security system details, see the G35 Body, Lock & Security System Manual 2003-2004.

After 28 years in the trade, I’ve learned that the fastest way to fix a car is to start with the right data. That means a factory diagnostic manual – not a generic service data subscription. The 2004 G35 ECM has enough complexity to trip up even experienced techs. The DTC index, the SRS precautions, the OBD drive patterns – they’re all in this manual. No wasted time, no re-diagnosis. Access the Factory Manual and get it on your workbench.

For broader context on diagnostics technology, see Automotive Industry Overview and On-board Diagnostics (OBD).