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DOHC2300 16V Engine and Manual Gearbox Control Loom

Based on the DOHC2000 Engine, the 2.3 has similar control functions, but with a new composite inlet manifold Ford claimed that it was efficient enough without the Variable Resonance Inlet system fitted to the 24V, hence the VIS valve control is deleted. The manual has no need of a second bulkhead connector, and the C110 is all that is needed.

Note: Remember that in several locations the Scorpio uses very thin wires which carry multiplex signals at 5V rather than more traditional 12V analogue signals used in almost all other vehicles. This makes the wiring looms and connectors much more susceptible to damage and is considered one of the weaknesses of the cars now they are in the secondhand market.

Circuit Description 

The electronic engine control system uses a network of sensors, switches, and solenoids and the PCM (A147) to control fuel flow, exhaust gas recirculation (EGR), ignition system functions, engine idle speed, fuel evaporation to the atmosphere and feedback functions for emission-related components. 


Voltage Supply 

With the ignition off, voltage is present at pin 55 of the PCM (A147) to protect the data stored in memory. With the ignition in run, the DIS ignition coils (T4, T5), and the fuel pump relay (K4) receive voltage. All other components of the engine control system receive voltage from the fuel pump relay (K4). Pins 71 and 97 of the PCM (A147) also obtain voltage from the fuel pump relay (K4). 

Ignition 

The ignition system is controlled by the PCM (A147). The DIS ignition coils (T4, T5) are controlled at pins 26 and 52 of the PCM (A147). The crankshaft position sensor (B43) is controlled at pins 21 and 22 of the (A147). 


Fuel Pump 

The fuel pump relay (K4) receives voltage from the ignition switch (N278) and is controlled by pin 80 (pin 54 with passive anti-theft system (PATS)) of the PCM (A147). Pin 40 of the PCM (A147) is used as a fuel pump monitor input. Current flows to the inertia switch (N61) which shuts off the fuel pump in the fuel tank unit (A31) in case of an accident. The fuel pump runs constantly during normal operation, and the system pressure is preserved when the engine is shut off. 

Power Steering Pressure Switch 

The power steering pressure switch (N96) sends a signal to pin 31 of the PCM (A147) when the pressure is high. Under high power steering pressure the PCM (A147) increases the idle speed. 

Engine Cooling Fan 

The engine cooling fan relay (K45) and the engine cooling fan motors (M37, M38) are controlled by pins 17 and 68 of the PCM (A147). 

Instrument Cluster 

The instrument cluster (A30) with integrated trip computer obtains a "fuel flow" value from pin 43 of the PCM (A147) in order to calculate fuel economy and distance-to-empty displays for the driver. 

A/C Compressor Control 

The A/C Wide Open Throttle (WOT) relay (K32) can be energised when pin 69 of the PCM (A147) is connected to ground. This will cause the A/C compressor to be disengaged, thus reducing engine load. 
Voltage is applied to pin 41 of the PCM (A147) when the dual pressure switch (N76) is closed. This information is used to determine engine load and to control engine idle speed. 

Octane Adjust 

Pin 30 of the PCM (A147) measures the voltage drop across the octane adjust plug (D2) and uses this information to modify ignition spark advance. 

Diagnostic and Ground Connections 

Pins 13, 15 and 16 of the PCM (A147) lead to the Data Link Connector (DLC) (D20). 
Pins 23, 24, 51, 77 and 103 of the PCM (A147) are connected to ground G10. 
Pin 25 of the PCM (A147) is connected to ground G7. 

Solenoids 

The fuel injectors (Y108, Y109, Y110, Y111) obtain their voltage from the fuel pump relay (K4). The PCM (A147) (pins 75, 101, 74 and 100 or pins 70, 96, 20 and 95 with passive anti-theft system (PATS)) controls the four fuel injectors continuously and individually. The injection quantity, that is, the duration of the input signal, is determined by the temperature, load and rpm of the engine as well as by the composition of the exhaust gases. The longer the pulse, the greater the amount of fuel that passes through the injector. 

The idle speed control valve (Y13) obtains its distribution voltage from the fuel pump relay (K4). The PCM (A147) compares the stored desired engine idle speed value with the actual engine idle speed and regulates the idle speed control valve (Y13) from pin 83. The idle speed control valve (Y13) varies the air volume into the engine via an auxiliary air passage. 

The canister purge solenoid valve (Y1) is needed to open and close the activated carbon canister. When the valve is energised by connecting pin 56 of the PCM (A147) to ground, the fuel vapours from the fuel tank can be drawn into the engine, mixed with the intake air and burned. 

The Electr. Vacuum Regulator (EVR) solenoid valve (Y33) allows a measured quantity of exhaust gas to be directed back into the intake manifold. The exhaust gas introduced into the intake manifold dilutes the incoming mixture and reduces peak gas temperatures, thus reducing NOx emissions. The valve is controlled by pin 47 of the PCM (A147). The EGR system does not operate during conditions of over-run or wide open throttle. 

Sensors 

Pin 91 of the PCM (A147) serves as ground for the Exhaust Pressure Transducer (EPT) sensor (B40), the clutch pedal switch (N81), the transmission switch (N276), the Throttle Position Sensor (TPS) (B8), the heated oxygen sensors (HO2S) (B89, B90), the Engine Coolant Temperature (ECT) sensor (B10), the Air Charge Temperature (ACT) sensor (B5), the power steering pressure switch (N96) and the octane adjust plug (D2). 

The Exhaust Pressure Transducer (EPT) sensor (B40) and the Throttle Position Sensor (TPS) (B8) receive a reference voltage of 5 V from pin 90 of the PCM (A147). 

The Exhaust Pressure Transducer (EPT) sensor (B40) measures the pressure difference in the feed exhaust and sends its signal to pin 65 of the PCM (A147). The sensor is part of the EGR system. 

The Throttle Position Sensor (TPS) (B8) consists of a potentiometer mounted on the throttle blade shaft that sends its signal to pin 89 of the PCM (A147). Using this signal, the module can compute the position of the throttle valve (idle, partial load, or wide open) and use the input to help calculate fuel delivery. 

The pre-catalyst heated oxygen sensor (HO2S) (B89) measures the amount of oxygen in the exhaust gases. Bounce signals are sent from the pre-catalyst heated oxygen sensor (HO2S) (B89) to pin 93 of the PCM (A147). This measurement is made so that the PCM (A147) can maintain the air/fuel mixture composition close to the value of Lambda=1 for correct operation of the catalytic converter. Since the sensor does not function until it has reached its operating temperature, it contains a heating element to shorten warm-up time. 

The post-catalyst heated oxygen sensor (HO2S) (B90) is installed behind the catalytic converter and sends bounce signals to pin 95 (pin 100 with passive anti-theft system (PATS)) of the PCM (A147) to ensure correct operation of the pre-catalyst heated oxygen sensor (HO2S) (B89). 

The Engine Coolant Temperature (ECT) sensor (B10) (a temperature-dependent resistor) receives its input voltage from pin 38 of the PCM (A147). The sensor provides the PCM (A147) with the engine operating temperature needed to help calculate fuel delivery. 

The Air Charge Temperature (ACT) sensor (B5) provides the PCM (A147), pin 39, with a signal proportional to the temperature of the incoming air charge. The data is used to help calculate fuel delivery. 

The Vehicle Speed Sensor (VSS) (B11) sends a square wave signal, whose frequency is proportional to the vehicle road speed, to pin 58 of the PCM (A147). 

The Mass Air Flow (MAF) sensor (B22) measures the quantity of air passing into the engine via the air filter. The information is then fed back to the PCM (A147), pins 36 and 88, and is used to help calculate fuel delivery. 

The crankshaft position sensor (B43) provides pins 21 and 22 of the PCM (A147) with the position of the crankshaft. This data is used for correct timing of the injectors at engine start-up. 

The camshaft position sensor (B41) provides the PCM (A147), pin 76, with a reference point for the number 1 cylinder, which is necessary to ensure the correct sequence of injector opening. 

Connections

The Powertrain Control Module is shown as C401 instead of C402 shown on the introduction page, but the two are identical.

Now a view of the connectors on the 2.3 engine.

Engine Loom Connections

Note, connections in square brackets indicate pins for vehicles not equipped with PATS.

Several other elements are not actually part of the loom. These can be checked by reference to the C401 connector on the PCM and the appropriate wire on the instrument - Terminal Nos on each multiplug given in the 3rd Column.:

Note, prior to 4/97 both Pre and Post catalysts are shown connected directly to the PCM. The post-catalyst is not shown on the diagrams for vehicles 4/97 on.

Using a digital multimeter it is hoped that this information will be sufficient to enable an owner to check his own looms for faults while leaving it in situ. Only if the Loom fails the tests will it be necessary to remove it. 

Don't forget to disconnect both ends of a loom before testing it, or you will be testing the apparatus it is connected to, rather than the loom.