Section 107 (Engine Controls - Trouble Shooting - No Codes): Introduction

WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2003 Infiniti QX4, 2003 Infiniti Q45, 2003 Infiniti M45, 2003 Infiniti I35, and 2003 Infiniti G35. However, it is still accessible from the selected car via links, so may be relevant.

The engine has an ECM to control major systems such as fuel control, ignition control, idle air control system, etc. The ECM accepts input signals from sensors and instantly drives actuators. It is essential that both input and output signals are proper and stable. At the same time, it is important that there are no incidents such as vacuum leaks, fouled spark plugs, or other incidents with the engine.

It is much more difficult to diagnose an incident that occurs intermittently rather than continuously. Most intermittent incidents are caused by poor electric connections or improper wiring. In this case, careful checking of suspected circuits may help prevent the replacement of good parts.

A visual check only may not find the cause of the incidents. A road test with CONSULT-II (or GST) or a circuit tester connected should be performed. Before undertaking actual checks, take a few minutes to talk with a customer who approaches with a driveability complaint. The customer can supply good information about such incidents, especially intermittent ones. Find out what symptoms are present and under what conditions they occur. Start your diagnosis by looking for "conventional" malfunctions first. This will help troubleshoot driveability malfunctions on an electronically controlled engine vehicle.