Acura Coupes and Sedans 1994-2000 Repair Information

General Information


Since the computer control module is programmed to recognize the presence and value of electrical inputs, it will also note the lack of a signal or a radical change in values. It will, for example, react to the loss of signal from the vehicle speed sensor or note that engine coolant temperature has risen beyond acceptable (programmed) limits. Once a fault is recognized, a numeric code is assigned and held in memory. The dashboard warning lamp: CHECK ENGINE or SERVICE ENGINE SOON (SES), will illuminate to advise the operator that the system has detected a fault. This lamp is also known as the Malfunction Indicator Lamp (MIL).

More than one code may be stored. Keep in mind not every engine uses every code. Additionally, the same code may carry different meanings relative to each engine or engine family.

Depending upon the year of your vehicle, it is either On-Board Diagnostic I (OBD I) of On-Board Diagnostic II (OBD II) compliant. All 1994-95 Integras, Legends and Vigors are OBD I compliant. All other models covered by this guide are OBD II compliant. Before beginning any procedure, make sure you have the correct system for your vehicle.

In the event of an computer control module failure, the system will default to a pre-programmed set of values. These are compromise values which allow the engine to operate, although possibly at reduced efficiency. This is variously known as the default, limp-in or back-up mode. Driveability is almost always affected when the ECM enters this mode.


The scan tool allows any stored codes to be read from the ECM or PCM memory. The tool also allows the operator to view the data being sent to the computer control module while the engine is running. This ability has obvious diagnostic advantages; the use of the scan tool is frequently required for component testing. The scan tool makes collecting information easier; the data must be correctly interpreted by an operator familiar with the system.

See Figure 1

Click image to see an enlarged view

Fig. Fig. 1: The use of a scan tool can save lots of valuable diagnostic time

An example of the usefulness of the scan tool may be seen in the case of a temperature sensor which has changed its electrical characteristics. The ECM is reacting to an apparently warmer engine (causing a driveability problem), but the sensor's voltage has not changed enough to set a fault code. Connecting the scan tool, the voltage signal being sent to the ECM may be viewed; comparison to normal values or a known good vehicle reveals the problem quickly.


The most commonly required electrical diagnostic tool is the digital multimeter, allowing voltage, ohmage (resistance) and amperage to be read by one instrument. The multimeter must be a high-impedance unit, with 10 megohms of impedance in the voltmeter. This type of meter will not place an additional load on the circuit it is testing; this is extremely important in low voltage circuits. The multimeter must be of high quality in all respects. It should be handled carefully and protected from impact or damage. Replace batteries frequently in the unit.

A digital storage oscilloscope is become increasingly necessary to diagnose today's cars. Although they are expensive to purchase, you may be able to rent one from an auto parts store. The oscilloscope is capable of displaying an electrical pattern rather then just measuring its value. This enables you to catch intermittent problems which a digital multimeter will miss.

Other necessary tools include an unpowered test light and a quality tachometer with an inductive (clip-on) pick up. The Micro-Pack connectors are used at the ECM electrical connector. A vacuum pump/gauge may also be required for checking sensors, solenoids and valves.


Do not operate the fuel pump when the fuel lines are empty.
Do not operate the fuel pump when removed from the fuel tank.
Do not reuse fuel hose clamps.
The washer(s) below any fuel system bolt (banjo fittings, service bolt, fuel filter, etc.) must be replaced whenever the bolt is loosened. Do not reuse the washers; a high-pressure fuel leak may result.
Make sure all ECU harness connectors are fastened securely. A poor connection can cause an extremely high voltage surge and result in damage to integrated circuits.
Keep all ECU parts and harnesses dry during service. Protect the ECU and all solid-state components from rough handling or extremes of temperature.
Use extreme care when working around the ECU or other components; the airbag or SRS wiring may be in the vicinity. On these vehicles, the SRS wiring and connectors are yellow; do not cut or test these circuits.
Before attempting to remove any parts, turn the ignition switch OFF and disconnect the battery ground cable.
Always use a 12 volt battery as a power source for the engine, never a booster or high-voltage charging unit.
Do not disconnect the battery cables with the engine running.
Do not disconnect any wiring connector with the engine running or the ignition ON unless specifically instructed to do so.
Do not apply battery power directly to injectors.
Whenever possible, use a flashlight instead of a drop light.
Keep all open flame and smoking material out of the area.
Use a shop cloth or similar to catch fuel when opening a fuel system. Consider the fuel-soaked rag to be a flammable solid and dispose of it in the proper manner.
Relieve fuel system pressure before servicing any fuel system component.
Always use eye or full-face protection when working around fuel lines, fittings or components.
Always keep a dry chemical (class B-C) fire extinguisher near the area.