Acura 3.5 RL, Manual

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PGM-FI System
System Description (cont'd)
3. Fuel Cut-off Control
• During deceleration with the throttle valve closed, current to the injectors is cut off to improve fuel economy at
speeds over 1,000 rpm.
• Fuel cut-off action also takes place when engine speed exceeds 5,900 rpm, regardless of the position of the throttle
valve, to protect the engine from over-revving.
4. A/C Compressor Clutch Relay
When the PCM receives a demand for cooling from the air conditioning system, it delays the compressor from being
energized, and enriches the mixture to assure a smooth transition to the A/C mode.
5. Evaporative Emission (EVAP) Control.
When the engine coolant temperature is above 99°F (37°C): '96 - 99 models, 140°F (60°C): '00 - 04 models, the PCM
controls the EVAP canister purge valve which controls vacuum to the EVAP canister.
6. Intake Manifold Runner Control (IMRC)
When engine speed is below 3,200 rpm, the IMRC Solenoid Valve 1 and IMRC Solenoid Valve 2 are activated by a sig-
nal from the PCM. Intake air flows through a long chamber path, increasing torque at low RPM.
When engine speed is 3,200 - 3,800 rpm, the IMRC Solenoid Valve is deactivated by the PCM. Intake air flows through a
short chamber path, increasing mid-range torque.
When the engine rpm is above 3,800 rpm, the IMRC Solenoid Valve 1 and IMRC Solenoid Valve 2 are deactivated by the
PCM. This creates a very short intake path and increases high-speed torque.
7. Exhaust Gas Recirculation (EGR) Control
When the EGR is required for control of oxides of nitrogen (NOx) emissions, the PCM controls the EGR control valve
vacuum solenoid valve which supplies regulated vacuum to the EGR valve.
ECM Fail-safe/Back-up Functions
1. Fail-safe Function
When an abnormality occurs in a signal from a sensor, the PCM ignores that signal and assumes a pre-programmed
value for that sensor that allows the engine to continue to run.
2. Back-up Function
When an abnormality occurs in the PCM itself, the fuel injectors are controlled by a back-up circuit independent of the
system in order to permit minimal driving.
3. Self-diagnosis Function [Malfunction Indicator Lamp (MIL)]
When an abnormality occurs in a signal from a sensor, the PCM supplies ground for the MIL and stores the DTC in
erasable memory. When the ignition is initially turned on, the PCM supplies ground for the MIL for 2 seconds to check
the MIL bulb condition.
4. Two Trip Detection Method ('96 - 97 models)
To prevent false indications, the Two Trip Detection Method is used for the HO2S, fuel metering-related, idle control
system, ECT sensor, EGR system self-diagnostic functions and EVAP control system. When an abnormality occurs, the
PCM stores it in its memory. When the same abnormality recurs after the ignition switch is turned OFF and ON (II)
again, the PCM informs the driver by lighting the MIL.
However, to ease troubleshooting, this function is cancelled when you short the service check connector. The MIL will
then blink immediately when an abnormality occurs.
5. Two Driving Cycle Detection Method ('96 - 97 models)
A "Driving Cycle" consists of starting the engine, beginning closed loop operation, and stopping the engine. If misfir-
ing that increases emissions, EVAP control system malfunction or TWC deterioration is detected during two consecu-
tive driving cycles, the PCM turns the MIL on.
However, to ease troubleshooting, this function is cancelled when you short the service check connector. The MIL will
then blink immediately when an abnormality occurs.
6. Two Driving Cycle Detection Method ('98 - 04 models)
To prevent false indications, the "two driving cycle detection method" is used for the HO2S, fuel metering-related, idle
control system, ECT sensor, EGR system, TWC and EVAP control system and other self-diagnostic functions. When an
abnormality occurs, the PCM stores it in its memory. When the same abnormality recurs after switch is turned OFF and
ON (II) again, the PCM informs the driver by turning on the MIL.