Ford F4TZ-12A697-A Sensor Assembly

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When working with the PCM (also known as the EEC-V module) or associated harness, exercise caution to avoid direct contact with the electrical connector terminals, as static electricity can damage delicate electronic components inside the PCM. It is recommended to wear a static discharging wrist strap and avoid working on electronics when relative humidity is under 25 percent. General EEC-IV power relay and ground checks are essential to prevent confusion and inaccurate diagnosis. The EEC relay and associated circuits provide battery power (VPWR) to fuel injection and electric fuel pump-related components requiring 10.5 volts or greater. The PCM (EEC-IV) reduces the input voltage to four-to-six volts for output to sensors requiring a specific reference voltage (VREF). For fuel delivery component and circuit checks, verify proper electrical operation of the fuel pump relay, inertia switch, fuel pump(s), fuel injectors, and fuel tank selector switch on dual tank models. Information sensors and output actuators include the engine coolant temperature sensor, which is a thermistor varying its voltage output based on temperature changes. Resistance values change with temperature, and failure in the coolant sensor circuit may set a diagnostic code. To check the sensor, measure its resistance values when cold and at operating temperature, ensuring correct values. Verify the signal voltage to the sensor from the PCM, which should be approximately 5.0 volts. Before installing a new sensor, wrap the threads with Teflon sealing tape. The Manifold Absolute Pressure (MAP) sensor monitors intake manifold pressure changes and converts them into a voltage output. There are voltage-varying and frequency-varying types of MAP sensors. A failure in the MAP sensor circuit may set a diagnostic code. Check the reference voltage to the MAP sensor and back probe the harness to determine the sensor type. Test the sensor response with a tachometer and a handheld vacuum pump, ensuring a smooth transition between readings. Replace the MAP sensor if test results are incorrect. The heated oxygen sensor (HO2S) monitors the oxygen content of the exhaust gas stream, producing a voltage output that varies with the air-to-fuel ratio. Diagnostic codes indicate problems in the oxygen sensor system. Check the sensor's steady signal voltage between 0.35 and 0.55 volts at normal operating temperature. The sensor's proper operation depends on electrical connections, outside air supply, operating temperature, and the use of unleaded fuel. Take special care during sensor service to avoid damage. When replacing the oxygen sensor, use caution due to the sensor's location in the exhaust manifold or pipe. Start and run the engine briefly before removal to facilitate loosening. Disconnect the battery, raise the vehicle, disconnect the electrical connector, unscrew the sensor, apply anti-seize compound to the threads, install the new sensor, and reconnect the electrical connector. The Throttle Position Sensor (TPS) is located on the throttle body and monitors throttle valve angle, affecting fuel delivery. Problems in the TPS or circuit may set a diagnostic code. To check the TPS, measure the signal voltage at idle and full-open throttle positions. Verify the TPS reference voltage and resistance of the potentiometer within the TPS. Adjust the TPS if necessary. The Intake Manifold Temperature Sensor, also known as the Air Charge Temperature (ACT) sensor, is located in the intake manifold and acts as a resistor changing value with air temperature. Problems with the IAT sensor may set a diagnostic code. Check the reference voltage and measure resistance across the sensor terminals at different temperatures. Power steering pressure switch issues may cause timing to retard at idle or engine stalling under heavy power steering use. A pressure switch that fails to open or close may impact engine performance. Check for battery voltage to the power steering pressure switch and continuity to brake light bulbs. The Brake On/Off (BOO) switch indicates brake application to the PCM. Issues with the BOO switch or circuit may affect idle quality. Check for battery voltage to the BOO switch and continuity to brake light bulbs. The EGR Valve Position (EVP) sensor attached to the EGR valve produces a signal indicating the EGR valve's position. Check for reference voltage and resistance of the EVP sensor. Apply vacuum and check resistance change. Replace the EVP sensor if necessary. The Knock Sensor (KS) detects engine detonation, sending a voltage signal to the PCM to retard spark timing. Check for reference voltage to the knock sensor and simulate operating conditions to observe timing response. Replace the knock sensor if it does not respond. The Idle Air Control (IAC) or Bypass Air Idle Speed Control (BPA-ISC) solenoid controls idle speed by regulating air bypassing the throttle body. Check for the PCM signal voltage, inspect the pintle for carbon deposits, and check the resistance of the solenoid. Clean the IAC valve housing and install a new O-ring during replacement. The Mass Airflow (MAF) sensor measures air entering the engine using a hot wire sensing element. Check for power to the MAF sensor and voltage signals at idle and increased engine speed. Disconnect the MAF sensor and check for resistance. Replace the MAF sensor if necessary. The Manual Lever Position (MLP) sensor on the transmission indicates the gear position to the PCM. Check for power to each signal wire and adjust the switch if necessary. Further diagnostics require specialized equipment.

If the following tests indicate that a sensor is good, and not the cause of a driveability problem or OTC, check the wiring harness and connectors between the sensor and the PCM for an open or short circuit. If no problems are found, have the vehicle checked by a dealer service department or other qualified repair shop. The Intake Manifold Temperature Sensor is a thermistor that changes resistance as temperature changes. The sensor is installed in the intake air duct to sense air temperature. As temperature increases, sensor resistance decreases and vice versa. The PCM uses this information to compute the intake temperature and fine tune fuel metering. A problem in the Intake Manifold Temperature Sensor circuit fault may be in the circuit wiring or connections or in the sensor itself. With the engine cool, disconnect the Intake Manifold Temperature Sensor and use an ohmmeter to measure sensor. For example, at 68-degrees F the ohms (Intake Manifold Temperature and Engine Coolant Temperature (ECT) sensors approximate temperature vs. resistance values). Next, start the engine and warm it up until it reaches operating temperature. Turn the engine off, disconnect the sensor and measure the resistance again. It should be lower. If the sensor resistance doesn't change as described, replace it. If the resistance values of the sensor are correct, check for reference voltage from the PCM to the sensor connector. The open-circuit voltage at the sensor connector should be approximately 5 volts. Disconnect the electrical connector, then carefully remove the Intake Manifold Temperature Sensor from the air intake duct. Be careful not to damage any of the plastic parts. Install and connect the new sensor.

A faulty power steering pressure switch may cause timing to retard at idle or engine stalling under heavy power steering use. Check for voltage and continuity to diagnose the issue.