Electronic Engine Contol Sensors

Component description and operation, removal and installation.

This section deals with the control sensors affiliated with the Electronic Engine Control (EEC) and the Powertrain Control Module (PCM). Various switch and sensor failures were commonly responsible for some drivability problems with the 1989 - 1995 Taurus SHO's, however these problems have yet to repeat themselves with the Third Generation car's. The following is a list of sensors, their operational description, and the removal and installation procedure, where applicable.

POWERTRAIN CONTROL MODULE (PCM)

The powertrain control module (PCM) performs the following functions:

The PCM accepts input from various engine sensors to compute the required fuel flow rate necessary to maintain a prescribed air/fuel ratio throughout the entire engineoperational range.
Then the PCM outputs a command to the fuel injectors to meter the appropriate quantity of fuel.
The PCM determines and compensates for the age of the vehicle and its uniqueness, also automatically senses and compensates for changes in altitude (i.e. from sea level to mountains).

Removal

1. Disconnect battery ground cable.
2. Remove cowl deflector.
3. Remove screw securing the ground cable of the engine control sensor wiring to the dash panel.
4. Loosen engine control sensor wiring to PCM connector retainer bolt.
5. Remove engine control sensor wiring from PCM.
6. Remove retaining nuts and powertrain control module insulator from dash panel.
7. Remove powertrain control module.

Installation

1. Follow removal procedure in reverse order.
2. Tighten insulator retaining nuts to 8-12 N-m (71-106 lb-in).
3. Tighten engine control sensor wiring retainer bolt to 3.7 N-m (32 lb-in).
4. Tighten engine control sensor wiring ground retaining screw securely.

Powertrain Control Module - Mounting

Item Part Number Description

1 12A659 Powertrain Control Module Bracket

2 N606676-S2 Bolt

3 N807718-S36 Nut

4 01610 Dash Panel

5 12B523 Insulator

6 N621905-S2 Nut (2 Req'd)

7 12A650 Powertrain Control Module

8 N808062-S36 Stud Bolt (2 Req'd)

A -- Tighten to 8-12 N-m (71-106 Lb-In)

THROTTLE POSITION (TP) SENSOR

The throttle position sensor (TP sensor) is:

a potentiometer that provides a signal to the powertrain control module (PCM). This signal is directly proportional to the throttle plate position.
mounted to the throttle body and connected to the throttle plate shaft.

Removal

1. Disconnect battery ground cable.
2. Disconnect engine control sensor wiring from throttle position sensor (TP sensor).
3. Remove two throttle position sensor retaining screws.
4. Remove throttle position sensor.

Installation

1. CAUTION: Slide rotary tangs into position over throttle shaft blade, then rotate throttle position sensor clockwise to installed position only. Failure to install the throttle position sensor in this manner may result in damage to throttle position sensor or excessive idle speeds.
Note: This throttle position sensor is not adjustable. Install throttle position sensor. Make sure rotary tangs on sensor are in proper alignment.
2. Secure throttle position sensor to throttle body with two retaining screws. Tighten to 2.8-3.8 N-m (25-33 lb-in).
3. Connect engine control sensor wiring to throttle position sensor.
4. Connect battery ground cable.

MASS AIR FLOW (MAF) SENSOR

The mass air flow sensor (MAF sensor):

is located between the engine air cleaner (ACL) and the throttle body.
uses a hot wire sensing element to measure the amount of air entering the engine. Air passing over the hot wire causes it to cool.
sends an analog voltage signal to the powertrain control module (PCM) to determine the intake air mass. The powertrain control module will then calculate the required fuel injector pulse width in order to provide the desired air/fuel ratio.

The mass air flow sensor hot wire sensing element and housing are calibrated as a unit and must be serviced as a complete assembly.

CAUTION: The mass air flow sensor (MAF sensor) is a calibrated unit. Service hot wire engine element and housing as a complete assembly.

Removal

1. Disconnect battery ground cable.
2. Remove air cleaner outlet tube as described in.
3. Disconnect engine control sensor wiring connector from mass air flow sensor.
4. Remove four retaining nuts from air cleaner cover.
5. Carefully remove mass air flow sensor. Discard gasket.

Installation

1. Position mass air flow sensor with new gasket onto air cleaner cover.
2. Install four retaining nuts. Tighten to 8-12 N-m (71-106 lb-in).
3. Install air cleaner outlet tube.
4. Connect engine control sensor wiring connector to mass air flow sensor.
5. Connect battery ground cable.
6. Start engine and check for vacuum leaks.

Item Part Number Description

1 9B659 Air Cleaner Outlet Tube

2 12B579 Mass Air Flow Sensor

3 -- Gasket

4 9600 Engine Air Cleaner

5 -- Nut (4 Req'd)

A -- Tighten to 8-12 N-m (71-106 Lb-In)

INTAKE AIR TEMPERATURE (IAT) SENSOR

The intake air temperature sensor (IAT sensor) changes resistance in response to intake air temperature. Resistance decreases as the surrounding air temperature increases, providing a signal to the powertrain control module (PCM) that indicates the temperature of the incoming intake air.

Note: The intake air temperature sensor (IAT sensor) is located in the engine air cleaner cover. When installing, use care not to damage plastic locking tabs.

Removal

1. Disconnect battery ground cable.
2. Disconnect engine control sensor wiring from intake air temperature sensor.
3. Turn intake air temperature sensor 90 degrees counterclockwise and remove from engine air cleaner cover.
4. Inspect intake air temperature sensor O-ring for damage or deterioration and replace as necessary.

Installation

1. Follow removal procedure in reverse order.

IDLE AIR CONTROL (IAC) VALVE

The idle air control valve (IAC valve):

is used to control engine idle speed.
is mounted on the intake manifold or throttle body (depending upon application) and allows air to bypass the throttle plate. The amount of air allowed to bypass is determined by the powertrain control module (PCM) and controlled by a duty-cycle signal.

Removal

1. Disconnect battery ground cable.
2. Disconnect the engine control sensor wiring from the idle air control valve (IAC valve) at the idle air control valve electrical connector.
3. Remove the two idle air control valve retaining bolts.
4. Remove the idle air control valve and idle air control gasket (IAC gasket).

Installation

1. Note: If scraping is necessary, be careful not to damage idle air control valve gasket surface or drop material into intake manifold or throttle body (depending upon application). Clean idle air control valve gasket mating surfaces.
2. Follow removal procedure in reverse order.
3. Tighten the idle air control valve retaining bolts to 8-12 N-m (71-106 lb-in).

ENGINE COOLANT TEMPERATURE (ECT) SENSOR

The engine coolant temperature sensor (ECT sensor) changes resistance in response to the temperature of the engine coolant. Resistance decreases as the surrounding temperature increases, providing a signal to the powertrain control module (PCM) that indicates the temperature of the engine coolant.

Removal

1. Drain engine cooling system.
2. Disconnect battery ground cable.
3. Remove the engine intake air resonator.
4. Disconnect engine control sensor wiring from engine coolant temperature sensor .
5. Remove engine coolant temperature sensor.

Installation

1. Follow removal procedure in reverse order.
2. Tighten engine coolant temperature sensor to 14-19 N-m (11-14 lb-ft).
3. Install the engine intake air resonator.

HEATED OXYGEN SENSOR (HO2S)

The heated oxygen sensors (HO2S):

are located in the exhaust system
react with the oxygen in the exhaust gases and generate a voltage based on this reaction.

A low voltage indicates too much oxygen or a lean condition.
A high voltage indicates not enough oxygen or a rich condition.

Removal

1. Disconnect battery ground cable.
2. On 3.0L (4V) engine, remove cowl extension and right side of leaf screen.
3. Disconnect engine control sensor wiring from heated oxygen sensors (HO2S). Do not remove harness connectors from the brackets.
4. Raise vehicle.
5. Note: If excessive force is needed to remove a heated oxygen sensor, lubricate with penetrating oil prior to removal. Remove heated oxygen sensors from exhaust manifolds using Oxygen Sensor Wrench T94P-9472A.

Installation

1. Follow removal procedure in reverse order.
2. Apply a coating of anti-seize compound to threads of heated oxygen sensor. Tighten heated oxygen sensors to 34-46 N-m (26-33 lb-ft).

CAMSHAFT POSITION (CMP) SENSOR

The camshaft position sensor (CMP sensor) is:

a variable-reluctance sensor.
triggered by the high-point mark on the LH exhaust camshaft sprocket.

Removal

1. Disconnect battery ground cable.
2. Disconnect engine control sensor wiring from camshaft position sensor (CMP sensor.)
3. Remove camshaft position sensor retaining bolt and remove camshaft position sensor from engine.

Installation

1. Make sure camshaft position mounting sensor surface is clean and that camshaft position sensor O-ring is in proper location on camshaft position sensor .
2. CAUTION: Do not overtighten camshaft position sensor retaining bolt or damage to camshaft position sensor or engine mounting surface may occur. Position camshaft position sensor onto engine and install retaining bolt. Tighten retaining bolt to 8-12 N-m (71-106 lb-in).
3. Connect engine control sensor wiring to camshaft position sensor.
4. Connect battery ground cable.

KNOCK SENSOR (KS)

The knock sensor (KS):

is used to detect engine detonation (spark knock).
sends a voltage signal to the powertrain control module (PCM).
is able to provide a signal which retards the ignition timing, as necessary.

POWER STEERING PRESSURE (PSP) SWITCH

The power steering pressure switch (PSP switch) is:

a normally closed switch that opens as pressure increases.
used to send a signal to the powertrain control module (PCM) to adjust idle speed. This compensates for the additional load on the engine.

Removal

1. Open hood.
2. Disconnect battery ground cable.
3. Disconnect electrical connector at power steering pressure switch (PSP switch.)
4. Remove power steering pressure switch from power steering auxiliary actuator.

Installation

1. Follow removal procedure in reverse order.
2. Replace O-ring on power steering pressure switch. Tighten power steering pressure switch to 7-14 N-m (62-123 lb-in).
3. Fill and bleed power steering system with Motorcraft MERCON Multi-Purpose (ATF) Transmission Fluid XT-2-QDX or equivalent meeting Ford MERCON specification. Check system for leaks and proper operation.

Item Part Number Description

1 3N803 Power Steering Auxiliary Actuator

2 -- Rack and Pinion Steering Gear

3 3R608 Power Steering Pressure, Return and Pump Outlet Line Connector Kit (Power Steering Return Port)

4 -- Mounting Bolt (Part of 3N803)

5 3R608 Power Steering Pressure, Return and Pump Outlet Line Connector Kit (Power Steering Inlet Port)

6 3N824 Power Steering Pressure Switch (Electrical Connector)

7 -- Electrical Connector (Part of 3N803)

A -- Tighten to 33-41 N-m (25-30 Lb-Ft)

VEHICLE SPEED SENSOR (VSS)

The vehicle speed sensor (VSS) is:

a Hall-effect pickup that sends a signal to the powertrain control module (PCM).
able to provide the VSS signal which tells the powertrain control module vehicle speed.

Contact Information

Item	Part Number	Description
1	12A659	Powertrain Control Module Bracket
2	N606676-S2	Bolt
3	N807718-S36	Nut
4	01610	Dash Panel
5	12B523	Insulator
6	N621905-S2	Nut (2 Req'd)
7	12A650	Powertrain Control Module
8	N808062-S36	Stud Bolt (2 Req'd)
A	--	Tighten to 8-12 N-m (71-106 Lb-In)