PART A - Engine, Engine Management and Turbocharger

2. Electronic Engine Management - System Sensors and Actuators

System Sensors (input) and Actuators (outputs)

Sensors

1 = Throttle Position Sensor (TPS)
2 = Manifold Absolute Pressure Sensor (MAP)
3 = Air Charge Temperature Sensor (ACT)
4 = Engine Coolant Temperature Sensor (ECT)
5 = Engine RPM / TDC-Sensor
6 = Distributor-Phase Sensor

Actuators
7 = Fuel Pump
8 = Fuel Injectors
9 = Idle Speed Control Valve (ISCV)
10 = Boost Pressure Control Valve (sometimes called AMAL)
11 = Ignition Module

General Description

The ECU module controls all fuel and ignition requirements of the engine by receiving, comput*ing and comparing sensor signals with its own permanent memory. Then it sends out signals to a series of actuators which control spark timing and fuel release.

The ECU is fitted behind the glove box and can be reached easily through a separate access lid. A 35 pin plug connects the ECU to the wiring loom.

Located next to the module are:
- the CO adjusting screw,
- a green, a blue and white cable for retarding the spark timing to meet fuels with lower octane rating
- and a self test connector:

Power to the ECU is supplied with a feed from the battery, via a relay.
For details see "Maintenance, Service Adjustments and System Checks".

ECU
1 = CO adjusting screw
2 = Module with multiplug
3 = Cable for retarding the spark timing
4 = Self test connector

The system sensors (inputs) are:

The Throttle Position Sensor (TPS)

This unit is fitted to the throttle shaft and senses the throttle position. At idle speed voltage is 5.0-4.5 volts and at full throttle the voltage drops to 0.5 volt.

The switch can be adjusted within the limits of its elongated fastening holes. (See "Service Adjustments".)

The Manifold Absolute Pressure (MAP) Sensor

The MAP-Sensor is fitted to the left fender apron and connected to the air chamber by a hose.
Depending on the manifold pressure, the Sensor regulates between 0.25 to 4.75 volts. If manifold pressure exceeds 0.9 bar, the sensor signals the ECU to cut-off fuel discharge by the injector valves.
The sensor cannot be adjusted or repaired.

The Air Charge Temperature (ACT) Sensor

This sensor is of the NTC resistor type, its resistance decreases as tempera*tures increase.
The ACT is screwed into the air chamber and can only be replaced as a unit if defective.
At 0° C, for example, the resistance is 9.75 kOhm and at 70° C the reading is 0.53 kOhm. Depending on the signal received from the ACT, the ECU module will vary the injection and ignition timing and also affect operation of the Turbocharger: (For further details see section "Turbocharger".)


Engine Coolant Temperature (ECT) Sensor

The ECT is also of NTC resistor type and its operating range is identical to that of the ACT.
The ECT is screwed into the cylinder*head and its signal to the module affects injector open time and idle speed.

Engine RPM and tdc Sensor

This sensor is bolted to the engine front end. The crankshaft pulley has 4 identical teeth spaced at precisely 90°. The sensor sends a signal to the module whenever a tooth passes the sensor. From this signal the module determines engine speed (RPM) and the TDC*position of each piston (crankshaft position) .
The gap between the sensor and the teeth on the crankshaft pulley is 0.4 to 1.0 mm and is factory set (see service adjustments).

The Phase Sensor-Distributor

This sensor is located inside the distributor. It's signals (and the signals from the RPM/TDC sensor) enable the ECU to identify the phase of each cylinder following the firing order.
The gap between the sensor and the teeth of the distributor cam is 0.2 to 0.3 mm and is factory set (see service adjustments).

RPM/TDC-Sensor
1 = Tooth on crankshaft pulley
2 = Sensor
A = 0 to 1.0mm

Phase Sensor-Distributor
1 = Sensor
2 = Tooth
A = 0.2 to 0.3 mm

After comparing sensor signals with its own permanent memory, the ECU sends out signals to a number of actuators (outputs).

These actuators are:

The Fuel Pump
The fuel pump is switched on and off via a relay when the engine is started or stalled.

The Fuel Injectors
The ECU provides accurate control of the solenoid operated fuel injectors to discharge fuel.

The Idle Speed Control (ISC) Valve
This unit regulates the engine demand for air depending on engine temperature, engine load, or switched on accessories.
When the throttle plate is in the closed position and engine speed is within the controlled idle speed range, air is allowed to bypass by means of the idle speed control valve. The valve, which is controlled by a variable current from the ECU, adjusts the air flow into the engine in order to maintain a constant idle speed.
With cold engine, the valve regulates speed above 1200 RPM.
With hot engine, the valve regulates speed below 1200 RPM only.
The valve is non-adjustable.

The Boost Pressure Control Valve (AMAL)

This solenoid valve is directly connect*ed to the high pressure side of the turbocharger by a hose. Depending upon whether the valve is open or closed it will either "vent-off" a portion of the boost to the inlet side of the compressor (valve open) or direct it to the waste gate actuator (valve closed). For further information see section "Turbocharger",

The Ignition Module

This module receives a signal from the ECU module to release a spark.