Mercury E7FZ-12A644-A Sensor Assembly

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The engine coolant temperature sensor is a thermistor that varies its voltage output based on temperature changes. Resistance values decrease as the sensor temperature increases and vice versa. Failure in the coolant sensor circuit triggers codes 21, 51, or 61 (two-digit) or 116, 117, 118 (three-digit). Resistance values should be checked while cold (58,750 to 40,500 ohms) and at operating temperature (3,600 to 1,840 ohms). Signal voltage to the sensor from the PCM should be around 5.0 volts. During replacement, wait for the engine to cool, use Teflon tape on threads, and handle the sensor with care.The Manifold Absolute Pressure (MAP) sensor monitors intake manifold pressure changes, converting them into a voltage output. A failure triggers codes 22 or 72 (two-digit) or 126, 128, 129 (three-digit). Check reference voltage (4.0 to 6.0 volts), backprobe the MAP/BP Signal wire, and apply vacuum to observe tachometer readings. Incorrect results indicate MAP sensor replacement.Oxygen sensors monitor exhaust oxygen content, adjusting air/fuel mixture. Check for a steady signal voltage between 0.35 and 0.55 volts at normal operating temperature. Codes 41, 42, 91, 92 (two-digit) or 136, 137, 139, 144, 171-178 (three-digit) indicate issues. Ensure the oxygen sensor heater receives battery voltage. Special care during service is essential.The Throttle Position Sensor (TPS) monitors throttle angle. Check for proper signal voltage (0.50 to 1.0 volts at idle, 4.0 to 5.0 volts at full throttle) and reference voltage (approximately 5.0 volts). Check potentiometer resistance (0.8 to 1.0 K ohms at closed throttle, 3.0 to 4.0 K ohms at full throttle). Replace if readings are incorrect.The Mass Air Flow (MAF) sensor, for 4.6L engines, measures air entering the engine. Check for power, signal voltage (0.2 to 1.5 volts at idle, increasing to about 2.0 volts at 60 mph), and use an ohmmeter for resistance checks. Replacement involves disconnecting the electrical connector, removing the air cleaner assembly, and uninstalling the MAF sensor.The Manual Lever Position (MLP) sensor, now Transmission Range (TR) sensor, indicates transmission gear. Check terminal connectors for attachment, verify power, and adjust if necessary. Diagnostics require special tools.The air conditioning clutch control involves PCM control of the compressor clutch. If the air conditioning does not function, check relays and switches. To test, remove the relay and bridge the battery feed and compressor clutch terminals. The Vehicle Speed Sensor (VSS) monitors speed, usually setting Code 24 if faulty. Check for signal voltage (10 volts or more). Replacement involves disconnecting the electrical connector, removing the retaining bolt, and lifting the VSS from the transmission. The Intake Manifold Temperature Sensor measures air temperature entering the engine. Check for correct reference voltage (5 volts) and resistance changes with temperature. Code 54 indicates issues.The power steering pressure switch affects idle quality. Problems may set Code 52. Check for open or closed circuits affecting engine timing.The crankshaft position sensor defines engine position for the PCM, and any issues require professional diagnosis. Replacement involves removing the electrical connector and retaining bolt.The camshaft position sensor is triggered by the camshaft sprocket's high point. Diagnostic work should be done by professionals.The Brake Light Switch informs the PCM when brakes are applied. Ensure proper voltage and continuity, and replace if needed. Brake light circuit and bulb conditions can impact idle quality.

The Electronic Engine Control (EEC-IV) system features an onboard computer called the Electronic Control Assembly (ECA) and various information sensors that monitor engine functions and relay data to the ECA, which then generates output signals to manage engine operations. The ECA, positioned inside the dashboard near the steering column, acts as the system's brain, processing data from multiple sensors and electronic components to optimize emissions, fuel economy, and drivability. Due to a federally mandated warranty covering the ECA and its components, diagnosing or replacing the ECA at home is discouraged; professional service is recommended for malfunctions. Input sensors include the compressor clutch signal, Air Charge Temperature sensor, Engine Coolant Temperature sensor, Manifold Absolute Pressure sensor, barometric pressure sensor, oxygen sensor, Profile Ignition Pick-up, and Throttle Position Sensor, all of which provide critical data for engine management. Output devices controlled by the ECA include the A/C and cooling fan controller module, EEC power relay, canister purge solenoid, EGR control solenoid, fuel injectors, fuel pump relay, and Idle Speed Control motor, with the TFI ignition module managing ignition timing. Diagnosing issues with these sensors and devices typically requires specialized equipment, making it advisable to seek dealer service for any driveability concerns. Component replacement should generally be avoided while under warranty, but after expiration, procedures for replacing the Air Charge Temperature sensor, Manifold Absolute Pressure sensor, Exhaust Gas Oxygen sensor, and canister purge solenoid can be performed, with specific steps outlined for each. However, replacing the Throttle Position Sensor is not recommended due to the need for specialized calibration equipment.

The MAP sensor monitors intake manifold pressure changes. To check it, verify the reference voltage, determine the sensor type, and test the sensor's response with a vacuum pump.