DOHC2000 16V Engine and Auto Gearbox Control Looms

Circuit Description 

The electronic engine control system uses a network of sensors, switches, and solenoids and the powertrain control module (PCM) (A147) to control fuel flow, exhaust gas recirculation (EGR), ignition system functions, engine idle speed, fuel evaporation to the atmosphere, transmission control 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 

With automatic transmission, the ignition system is controlled by the electronic Distributorless Ignition System (DIS) module (A23). The electronic DIS module (A23) controls the DIS ignition coils (T4, T5) and the crankshaft position sensor (B43) and is connected to pins 23, 48, 49, and 50 of the PCM (A147). The signal from pin 50 is used to detect intermittent ignition system faults. Pin 49 receives a Profile Ignition Pickup (PIP) value which is used by the PCM (A147) to determine crankshaft position. The PCM (A147) also uses the PIP-Signal to control gear shifting times (engine speed). 

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. 

Transmission Control 

The transmission hardware unit THU (A40) consists of the Transmission Speed Sensor (TSS), the Transmission Oil Temperature (TOT) sensor and five solenoids. The PCM (A147) provides outputs to the transmission through pins 1, 53, 54 (pins 72 and 80 with passive anti-theft system (PATS)) to control the shifting operations of the transmission. 

The stop lamp switch (N15) sends a "brake applied" signal to pin 92 of the PCM (A147). This data is used to adjust the engine operations during deceleration. 

Pins 10, 79 and 80 of the PCM (A147) lead to the instrument interface module (A35). 

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 pin 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 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 Electronic 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. 

The intake air control valve (Y67) receives voltage from the fuel pump relay (K4) and is controlled by pin 44 of the PCM (A147). 

Sensors 

Pin 91 of the PCM (A147) serves as ground for the Exhaust Pressure Transducer (EPT) sensor (B40), the Barometric Air Pressure (BAP) sensor (B70), 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 transmission range sensor (B120), the oil temperature sensor of the transmission hardware unit (A40), the power steering pressure switch (N96) and the octane adjust plug (D2). 

The Exhaust Pressure Transducer (EPT) sensor (B40), the Barometric Air Pressure (BAP) sensor (B70) and the Throttle Position Sensor (TPS) (B8) all 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 Barometric Air Pressure (BAP) sensor (B70) measures barometric pressure and sends its signal information to pin 34 of the PCM (A147). This information is used to help calculate fuel delivery. 

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 60 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 speed warm-up time. 

The post-catalyst heated oxygen sensor (HO2S) (B90) is installed behind the catalytic converter and sends bounce signals to pin 35 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 transmission range sensor (B120) sends a start input signal to pin 64 of the PCM (A147). The PCM (A147) will not allow the engine to start unless the transmission is in park (P) position. 

The Transmission Oil Temperature (TOT) sensor of the transmission hardware unit (A40) sends its signal to pin 37 of the PCM (A147). 

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 the electronic DIS module (A23), pins 5 and 6, with the position of the crankshaft. This data is used for correct timing of the injectors at engine start-up. 

The Transmission Speed Sensor (TSS) of the transmission hardware unit (A40) provides the PCM (A147), pin 84, with the transmission shaft speed. The data is used to control the shifting sequence for the transmission. 

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. 

Connectors

Below is the figure showing the locations of the connectors on the DOHC 2000 engine.

Gearbox (THU) Loom Connections

[Without PATS]

Engine Loom Connections

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

In addition, some modules or sensors essential for engine management are not connected directly to the PCM. The Electronic Distribution & Ignition System is one: terminal numbers on the EDIS module connector C766 are given in column 1.

Several other elements are not actually part of the loom. These can be checked by reference to the C402 connector on the PCM and the appropriate wire on the instrument - Terminal nos on each multiplug given in the 3rd Column.:

So, following these tables, we can see that Shift Solenoid #3 is connected to pin 53 on the PCM with a Black/Orange wire which goes through Terminal 27 on the large square connector C112 on the LH engine bulkhead. Looking at the figure of C112 we see that pin 27 is the right of the topmost two pins on the lower half, left of the top two on the upper half of the connector. This wire terminates in Pin 7 of the C604 connector on the gearbox, which is the the second row from the top, one from the right.

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. The owner will also be in a much stronger position when deciding if a fault really is a gearbox before paying for a new one!

Many thanks to Ford (Europe), without whose help these pages would not be possible.