Acura RL. Manual - part 514

Fig. 29: Identifying CKP Sensor And CKP Sensor Subharness
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Engine Coolant Temperature (ECT) Sensors 1 and 2

ECT sensors 1 and 2 are temperature dependent resistors (thermistors). The resistance of the thermistor
decreases as the engine coolant temperature increases.

Fig. 30: Identifying Terminal And O-Ring Of Engine Coolant Temperature Sensors
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Ignition Timing Control

The PCM contains the memory for basic ignition timing at various engine speeds and manifold absolute
pressures. It also adjusts the timing according to engine coolant temperature.

Injector Timing and Duration

The PCM contains the memory for basic discharge duration at various engine speeds and manifold
pressures. The basic discharge duration, after being read out from the memory, is further modified by
signals sent from various sensors to obtain the final discharge duration.

By monitoring long term fuel trim, the PCM detects long term malfunctions in the fuel system and sets a
diagnostic trouble code (DTC).

Intake Air Temperature (IAT) Sensor

The IAT sensor is a temperature dependent resistor (thermistor). The resistance of the thermistor decreases
as the intake air temperature increases.

2007 Acura RL

2005-08 ENGINE PERFORMANCE Fuel and Emissions Systems - RL

Friday, June 05, 2009 2:33:27 PM

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Fig. 31: Identifying O-Ring, Terminal And Thermistor Of Intake Air Temperature Sensor
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Knock Sensor

The knock control system adjusts the ignition timing to minimize knock.

Fig. 32: Identifying Piezo Ceramic Element, Diaphragm Of Knock Sensor
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Malfunction Indicator Lamp (MIL) Indication (In relation to Readiness Codes)

The vehicle has certain "readiness codes" that are part of the on-board diagnostics for the emissions systems.
If the vehicle's battery has been disconnected or gone dead, if the DTCs have been cleared, or if the PCM
has been reset, these codes are reset. In some states, part of the emissions testing is to make sure these codes
are set to complete. If all of them are not set to complete, the vehicle may fail the test, or the test cannot be
finished.

To check if the readiness codes are set to complete, turn the ignition switch ON (II), but do not start the
engine. The MIL will come on for 15-20 seconds. If it then goes off, the readiness codes are complete. If it
flashes five times, one or more readiness codes are not complete. To set each code, drive the vehicle or run
the engine as described in How to Set Readiness Codes (see MALFUNCTION INDICATOR LAMP
(MIL) INDICATION (IN RELATION TO READINESS CODES) ).

Manifold Absolute Pressure (MAP) Sensor

The MAP sensor converts manifold absolute pressure into electrical signals to the PCM.

2007 Acura RL

2005-08 ENGINE PERFORMANCE Fuel and Emissions Systems - RL

Friday, June 05, 2009 2:33:27 PM

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Fig. 33: Identifying Terminal And O-Ring Of Manifold Absolute Pressure Sensor
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Secondary Heated Oxygen Sensor (Secondary HO2S)

The secondary HO2S detects the oxygen content in the exhaust gas downstream of the warm up three way
catalytic converter (WU-TWC), and sends signals to the PCM. To stabilize its output, the sensor has an
internal heater. The PCM compares the HO2S output with the A/F sensor output to determine catalyst
efficiency. The secondary HO2S is on the WU-TWC.

Fig. 34: Identifying Secondary Heated Oxygen Sensor Parts Location
Courtesy of AMERICAN HONDA MOTOR CO., INC.

ELECTRONIC THROTTLE CONTROL SYSTEM

The throttle is electronically controlled by the electronic throttle control system. Refer to the system diagram
to see a functional layout of the system.

Idle control: When the engine is idling, the PCM controls the throttle actuator to maintain the proper idle
speed according to engine loads.

Acceleration control: When the accelerator pedal is pressed, the PCM opens the throttle valve depending on
the accelerator pedal position (APP) sensor signal.

Cruise control: The PCM controls the throttle actuator to maintain set speed when the cruise control is
operating. The throttle actuator takes the place of the cruise control actuator.

Accelerator Pedal Position (APP) Sensor

As the accelerator pedal position changes, the sensor varies the signal voltage to the PCM.

2007 Acura RL

2005-08 ENGINE PERFORMANCE Fuel and Emissions Systems - RL

Friday, June 05, 2009 2:33:27 PM

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Fig. 35: Identifying APP Sensor A/B And Accelerator Pedal
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Throttle Body

The throttle body is a single-barrel side draft type. The lower portion of the throttle valve is heated by
engine coolant from the cylinder head to prevent icing of the throttle plate.

Fig. 36: Identifying Throttle Valve, Throttle Position (TP) Sensor A/B And Throttle Actuator
Courtesy of AMERICAN HONDA MOTOR CO., INC.

IDLE CONTROL SYSTEM

When the engine is cold, the A/C compressor is on, the transmission is in gear, the brake pedal is pressed,
the power steering load is high, or the alternator is charging, the PCM controls current to the throttle
actuator to maintain the correct idle speed.

Brake Pedal Position Switch

The brake pedal position switch signals the PCM when the brake pedal is pressed.

2007 Acura RL

2005-08 ENGINE PERFORMANCE Fuel and Emissions Systems - RL

Friday, June 05, 2009 2:33:27 PM

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