Mercury FOVY-7A247-A Switch - Neutral Sensing

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To check the operation of the neutral safety switch, apply the parking brake and try to start the engine in each position of the selector lever. The engine should start only in Park and Neutral. If it starts in any other position, adjust the shift linkage and retest. If the engine still starts in any position other than Park or Neutral, replace the switch. To replace the switch, disconnect the cable from the negative battery terminal, place the shift lever in Low and apply the parking brake. Raise the vehicle and place it securely on jackstands. Unplug the electrical connector from the neutral safety switch. Carefully unscrew the switch and O-ring. Install the switch and new O-ring, tightening it to the specified torque. Be cautious not to crush or puncture the walls of the switch. Install the electrical connector and connect the negative battery cable. Verify that the engine starts only when the selector is in the Neutral and Park positions. The AODE transmission used on 1992 through 1994 models does not have a neutral safety switch. That function has been incorporated into an information sensor known as the Manual Lever Position (MLP) sensor. And 1995 and later models, which are equipped with a 4R70W transmission, use a transmission range (TR) sensor, a similar device.

To check the operation of the neutral safety switch, apply the parking brake and try to start the engine in each position of the selector lever. The engine should start only in Park and Neutral. If it starts in any other position, adjust the shift linkage and retest. If the engine still starts in any position other than Park or Neutral, replace the switch. To replace the switch, disconnect the cable from the negative battery terminal, place the shift lever in Low and apply the parking brake. Raise the vehicle and place it securely on jackstands. Unplug the electrical connector from the neutral safety switch. Carefully unscrew the switch and O-ring. Install the switch and new O-ring, tightening it to the specified torque. Be cautious not to crush or puncture the walls of the switch. Install the electrical connector and connect the negative battery cable. Verify that the engine starts only when the selector is in the Neutral and Park positions. The AODE transmission used on 1992 through 1994 models does not have a neutral safety switch. That function has been incorporated into an information sensor known as the Manual Lever Position (MLP) sensor. And 1995 and later models, which are equipped with a 4R70W transmission, use a transmission range (TR) sensor, a similar device.

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.

Engine can be started in every gear. The engine should only run if the clutch pedal has been stepped on (for manual cars) or when the car is in either Park or Neutral (for automatic vehicles). Ensure that the steering column lock will allow the key to turn to "Lock" position only when the shift lever is in Park. The key must not be released unless it is turned to Lock.

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 Transmission Range (TR) sensor informs the PCM about gear positions and activates the back-up lights. If the engine starts in any gear other than Park or Neutral, the TR sensor might be faulty. To test, raise the vehicle, switch the ignition to On, and shift into Reverse. If back-up lights don't come on, detach the shift cable, adjust the sensor until lights illuminate, then reattach the cable. If lights still don't come on, check the circuit and back-up lights. To replace the sensor, raise the vehicle, unplug the sensor's electrical connector, detach the shift cable, and remove the sensor. Install a new sensor, ensure correct adjustment, tighten the screws, then lower the vehicle.

The Transmission Range (TR) sensor informs the PCM about gear positions and activates the back-up lights. If the engine starts in any gear other than Park or Neutral, the TR sensor might be faulty. To test, raise the vehicle, switch the ignition to On, and shift into Reverse. If back-up lights don't come on, detach the shift cable, adjust the sensor until lights illuminate, then reattach the cable. If lights still don't come on, check the circuit and back-up lights. To replace the sensor, raise the vehicle, unplug the sensor's electrical connector, detach the shift cable, and remove the sensor. Install a new sensor, ensure correct adjustment, tighten the screws, then lower the vehicle.

Engine can be started in every gear. The engine should only run if the clutch pedal has been stepped on (for manual cars) or when the car is in either Park or Neutral (for automatic vehicles). Ensure that the steering column lock will allow the key to turn to "Lock" position only when the shift lever is in Park. The key must not be released unless it is turned to Lock.

Place the shift lever in Low.

The TR sensor serves as an information sensor for the powertrain control module (PCM) and performs functions similar to a Park/Neutral switch. It prevents the engine from starting in any gear other than Park or Neutral and activates the back-up lights when the shift lever is in Reverse. It also includes the sensing circuit for Neutral in 4X4 Low range on 4WD models.

Disconnect the electrical connector from the neutral start switch.

Deactivate the air suspension system by turning off the air suspension switch, which is located on the right kick panel.

The function has been incorporated into an information sensor known as the Manual Lever Position (MLP) sensor.

Codes 21, 51, or 61 (two-digit) or 116, 117, 118 (three-digit) indicate a failure in the coolant sensor circuit.

It is easy to crush or puncture the walls of the switch.

No, the AODE and 4R70W transmissions used on these vehicles do not have a neutral switch. That function has been incorporated into an information sensor known as the Manual Lever Position (MLP) sensor or, on 1995 and later models, the Transmission Range (TR) sensor.

Follow the transmission shift control cable adjustment and check for a distinct "click" when the shift lever selects each gear (Park, Reverse, Neutral, Drive, etc.).

To check the operation of the neutral start switch, apply the parking brake and try to start the engine in each position of the selector lever. The engine should start only in Park and Neutral. If it starts in any other position, adjust the shift linkage and retest. If the engine still starts in any position other than Park or Neutral, replace the switch.