Last update:

08/03/2005

  2.5 Tdi up to 9/96

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2.5 Tdi up to 9/96
2.5 Tdi 9/96 on

 

2.5 TDI Diesel to 9/96 (All Manual)

The TDI model was with manual transmission only until 9/96, when an automatic was announced. In the intervening period the Powertrain Control Module (PCM) changed, and some engine controls between 3/96 and 9/96 were revised.

Circuit Description (before 03/96) 

Cold Start System 

Ignition On 

With the ignition switch (N278) in position 2 (run), the diesel pre-glow relay (K70) receives voltage. The pre-glow warning light in the instrument cluster (A30) illuminates and the glow plugs (P20) receive voltage. The warning light remains on until the pre-glow period is over. 

Starting the Engine 

While the engine is being started (ignition switch (N278) in position 3 (start)), the glow plugs (P20) continue to receive current from the diesel pre-glow relay (K70). 

Engine Running 

During the engine warm-up period, the glow plugs (P20) continue to receive current until a certain engine temperature is reached. 

Powertrain Control Module (PCM) 

The powertrain control module (PCM) (A147) has been programmed specifically for various engine types. The module stores all information necessary to ensure precise exhaust gas recirculation. Based on input signals from various sensors, the actual values are compared to the stored desired values and if necessary, control or adjust signals are sent to the respective components. 

Injection Control 

The diesel cold advance valve solenoid (Y83) adjusts the injection timing to "early" with help from the injector valve (Y63). The injection timing must be adjusted to achieve optimal combustion under various load and rpm conditions. 
A needle motion sensor in the injector valve (Y63) adjusts the injection timing to "early". After the engine has reached its operating temperature, the diesel cold advance valve solenoid (Y83) is turned off. 

Exhaust Gas Recirculation (EGR) 

The Exhaust Gas Recirculation (EGR) system is controlled by the EGR solenoid valve (vacuum) (Y49) which is connected to pins 42 and 43 of the PCM (A147). The EGR solenoid valve (Y49) opens a bypass between the exhaust and intake manifolds. Additional signals to the PCM (A147) from the engine speed sensor (B7), the Engine Coolant Temperature (ECT) sensor (B10) and the Throttle Position Sensor (TPS) (B8) also influence the EGR system. 

Sensors 

The Fuel Lever Variable Resistor (FLVR) sensor (B98) is a potentiometer which sends a signal of the fuel lever position to pin 51 of the PCM (A147). Using this information, the PCM (A147) calculates fuel delivery depending on the engine load (idle, partial load, wide open). The Fuel Lever Variable Resistor (FLVR) sensor (B98) receives a 5 V reference voltage from pin 50 and is earthed at pin 52 of the PCM (A147). 

The engine speed sensor (B7), an inductive pulse generator, sends an alternating voltage signal to the PCM (A147). The signal serves as information about the engine rpm and is used in determining the injection timing. The engine speed sensor (B7) is connected to pins 54 and 55 of the PCM (A147). 

The Engine Coolant Temperature (ECT) sensor (B10), a temperature-dependent resistor, is connected to pins 53 and 58 of the PCM (A147). The ECT sensor (B10) provides the PCM (A147) with the engine temperature, which is then used to calculate the corresponding cold start adjustment, the amount of exhaust gas necessary for exhaust gas recirculation and, at high temperatures, air conditioning cut-off. 


Diagnostic and Ground Connections 

Pins 27 and 45 of the PCM (A147) lead to pins 3 and 11 of the Data Link Connector (DLC) (D20). 
Pins 40 and 60 of the PCM (A147) are connected to the negative battery terminal (ground). Pin 20 of the PCM (A147) is connected to ground G7 via splice S77. 

Fuel Heater 

The fuel heater (R32) warms the diesel fuel to prevent a paraffin separation at cold temperatures. The heating element consists of a ceramic resistor whose resistance increases with increasing temperature. The resistor is protected from overheating by an integrated thermoswitch and reaches a maximum temperature of 130 C. 

Connections.

The following tables are for the 2.5 TDI produced between 10/94 and 9/96. They should not be used for later models where there was a change of PCM and a completely different loom was introduced. 

Additional changes in engine controls between 3/96 and 9/96 are concerned with the wiring to the fuel shut-off valve and fuel heater and do not effect the wiring for the PCM.

The PCM multiplug, C464, is unique to this model. The location of the PCM is still behind the glovebox under the dash and is reached in the same way as the petrol models.

The engine connections are C132 and C135. They are also of a completely different design to petrol models, but are in the same location - on the driver's side engine bulkhead. Note - LHD model shown.

You will note that although the connections have identical numbering the wiring colours are different.

Engine Connections thru Engine Loom.

PCM C464 C and Pin No Colour & Useage Connector & Pin
52 C135    6 BN  Fuel Lever Variable Resistor (FLVR)  C869 Pin 1
51 C135  10 WH FLVR C869 Pin 2
50 C135    9 YE   FLVR C869 Pin 3
55 C132    5 BN/GN Engine Speed Sensor (ESS) C732 Pin 1
54 C132    2  WH/GN  ESS C732 Pin 2
46 C135    1  VT/BU Diesel Cold Advance solenoid (DCA) C887 Pin 1
41 C135    5 BK/BU DCA C887 Pin 2
53 C132    6 WH/VT Engine Coolant Temp (ECT) C886 Pin 2
58 C132    7 BN/WH ECT C886 Pin 1
56 C132    8 VT/WH Injector Valve C731 Pin 1
38 C132   12 BK/WH Injector Valve C731 Pin 2

Connections not thru Engine loom

Other sensors do not pass through the engine connectors and can be tested between the PCM connector and the unit itself.

PCM C464 Colour & Useage Connector Pin No
42 VT/BK  EGR solenoid valve C939 2
43 BK/GN EGR solenoid valve C939 1
22 BK/YE Pre Glow relay C786 Not shown
44 BK/YE Pre Glow relay C786 Not shown
40 Test for good ground - -
60 Test for good ground - -

When testing the loom remember to disconnect both ends of the wiring before running the test!

 

Good Luck

 

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

 

 

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