Acura TSX / Honda Accord CL. Manual - part 562

Fig. 38: Cutaway View Of Engine Coolant Temperature (ECT) Sensor 

IGNITION TIMING CONTROL 

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

INJECTOR TIMING & DURATION 

The ECM/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 ECM/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. 

 

2004 Acura TSX 

2004 ENGINE PERFORMANCE Fuel & Emissions Systems - TSX

  

 

Fig. 39: Cutaway View Of Intake Air Temperature (IAT) Sensor 

KNOCK SENSOR 

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

 

2004 Acura TSX 

2004 ENGINE PERFORMANCE Fuel & Emissions Systems - TSX

  

 

Fig. 40: Cutaway View Of Knock Sensor 

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 ECM/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 

 

2004 Acura TSX 

2004 ENGINE PERFORMANCE Fuel & Emissions Systems - TSX

  

 

times, one or more readiness codes are not complete. To set each code, drive the vehicle or run the engine as 
described in the procedures in this section (see HOW TO SET READINESS CODES ). 

MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR 

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

Fig. 41: Cutaway View Of Manifold Absolute Pressure (MAP) Sensor 

SECONDARY HEATED OXYGEN SENSOR (SECONDARY HO2S) 

The secondary HO2S detects the oxygen content in the exhaust gas downstream of the three way catalytic 
converter (TWC), and sends signals to the ECM/PCM which varies the duration of fuel injection accordingly. 
To stabilize its output, the sensor has an internal heater. The ECM/PCM compares the HO2S output with the 
A/F sensor output to determine catalyst efficiency. The secondary HO2S is located on the TWC.

 

2004 Acura TSX 

2004 ENGINE PERFORMANCE Fuel & Emissions Systems - TSX