Fuel and Emissions Systems
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11-15 |
ECM Data
You can retrieve data from the ECM by connecting the scan tool to the Data Link Connector (DLC). The items listed in the table below conform to SAE recommended practice.
NOTE:
| Data | Description | Operating Value | Freeze
Data |
| Engine Speed | Engine speed is computed by the ECM from the signals sent from the Crank 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: 850 + 50 rpm (min-1) | |
| 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: Nearly the same as ambient temperature and IAT.
With engine warmed up: about 80 – 100 °C (176 – 212 °F), 0.8 – 0.5 V. |
|
| Vehicle Speed | The ECM converts pulse signals from vehicle speed sensor (VSS). | Nearly the same as speedometer indication. | |
| Engine Load | The ECM calculates engine load based on injection rate.
Final injection (Q-Final)/Maximum permission injection (Q-Full) x 100 % = Engine load |
About 17 – 23 % at idle speed | |
| Manifold Absolute Pressure (MAP) | Boot pressure governing is used to control an exhaust turbocharger with Waste-Gate as well as a turbocharger with variable turbine geometry (VTG-turbocharger).
For governing an exhaust turbocharger with Waste-Gate the actuator is a bypass valve through which the exhaust flow is directed to or past the turbine. For governing a VTG-turbocharger the actuator is the variable turbine geometry. Boost pressure governing is subdivided into recognition of driving habits, setpoint valve calculation, boost pressure governor (closed-loop control), boost pressure open loop control, controlled adaption of governor parameters and monitoring and shut off. |
With engine stopped: Nearly the same as atmospheric pressure.
At idle engine: About 20 – 30 kPa (150 – 260 mmHg, 6 – 10 in. Hg), 0.7 – 1.1 V. |
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| Mass air Flow (MAF) | The ECM converts frequency signals from mass air flow sensor (MAF).
This indicates the amount of air entering the engine. |
About 8 – 13 g/sec at idle speed | |
| Throttle Position (TP) Sensor (Accelerator Pedal Position (APP) Sensor) | Based on the accelerator pedal position, the opening angle of the throttle valve is indicated. | About 0 – 10 % at idle speed | |
| Intake Air Temperature (IAT) | The IAT sensor converts intake air temperature into voltage and signals the ECM. When intake air temperature is low, the internal resistance of the sensor increases, and the voltage signal is higher. | With cold engine: Same as ambient temperature and ECT. | |
| Stored DTCs | Stored DTCs are used to detect to stored DTC quantity | 0 at normal | |
| OBD | Not used | Not used |