Fuel and Emissions Systems

System Descriptions (cont'd)


ECM Data

You can retrieve data from the ECM by connecting the scan tool or the Honda PGM Tester to the Data Link Connector (DLC). The items listed in the table below conform to SAE recommended practice. The Honda PGM Tester also reads data beyond that recommended by SAE so that this data may help you find the causes of intermittent problems.


  • The ''operating values'' listed are approximate and may vary depending on the environment and the individual vehicle.
  • Unless noted otherwise, ''at idle speed'' means idling with the engine completely warmed up in neutral position, and the A/C and all accessories turned off.
    Data Description Operating Value Freeze Data
    Diagnostic Trouble Code (DTC) If the ECM detects a problem, it will store it as a code consisting of one letter and four numbers. Depending on the problem, an SAE-defined code (P0xxx) or a Honda-defined code (P1xxx) will be output to the tester. If no problem is detected, there is no output. YES
    Engine Speed The ECM computes engine speed from the signals sent from the Crankshaft Position (CKP) sensor. This data is used for determining the time and amount of injected fuel. Nearly the same as tachometer indication

    At idle speed: 780 + 50 rpm (min-1)

    Vehicle Speed The ECM converts pulse signals from the Vehicle Speed Sensor (VSS). Nearly the same as speedometer indication YES
    Manifold Absolute Pressure (MAP) The absolute pressure caused in the intake manifold by engine load and speed. With engine stopped: Nearly the same as atmospheric pressure

    At idle speed: about 20 - 34 kPa (150 - 260 mmHg, 6 - 10 in.Hg), 0.7 - 1.1 V

    Engine Coolant Temperature (ECT) The ECT sensor converts coolant temperature into voltage and signals the ECM. The sensor is a thermistor whose internal resistance changes with coolant temperature. The ECM uses the voltage signals from the ECT sensor to determine the amount of injected fuel. With cold engine: Same as ambient temperature and IAT

    With engine warmed up: about 80 – 100°C (176 – 212°F), 0.5 - 0.8 V

    Primary Heated Oxygen Sensor (Primary HO2S) (Sensor 1), Secondary Heated Oxygen Sensor (Secondary HO2S) (Sensor 2) The HO2S detects the oxygen content in the exhaust gas and sends voltage signals to the ECM. Based on these signals, the ECM controls the air fuel ratio. When the oxygen content is high (that is, when the ratio is leaner than the stoichiometric ratio), the voltage signal is lower. When the oxygen content is low (that is, when the ratio is richer than the stoichiometric ratio), the voltage signal is higher. 0.0 - 1.25 V

    At idle speed:

    about 0.1 - 0.9 V