Testing Ford Sensors Part 1

(PCM). The PCM receives data from a number of sensors and other electronic components (switches, relay, etc.).

Based on information received and information programmed in the PCM’s memory, it generates output signals to control various relay, solenoids and other actuators.

The PCM in the EEC system has calibration modules located inside the assembly that contain calibration specifications for optimizing emissions, fuel economy and drive ability.

The calibration module is called a PROM. (Programmable Read Only Memory)

The following are the electronic engine controls used by 1991–99 Taurus, Ranger/Explorer and Mountaineers:

Powertrain Control Module (PCM) (Dealership)

Throttle Position (TP) sensor

Mass Air Flow (MAF) sensor

Intake Air Temperature (IAT) sensor

Idle Air Control (IAC) valve

Engine Coolant Temperature (ECT) sensor

Heated Oxygen Sensor (HO2S)

Camshaft Position (CMP) sensor

Knock Sensor (KS) (No information)

Vehicle Speed Sensor (VSS) (No information)

Crankshaft Position (CKP) sensor

The MAF sensor (a potentiometer) senses the position of the airflow in the engine’s air induction system and generates a voltage signal that varies with the amount of air drawn into the engine.

The IAT sensor (a sensor in the area of the MAF sensor) measures the temperature of the incoming air and transmits a corresponding electrical signal.

Another temperature sensor (the ECT sensor) inserted in the engine coolant tells if the engine is cold or warmed up.

The TP sensor, a switch that senses throttle plate position, produces electrical signals that tell the PCM when the throttle is closed or wide open.

A special probe (the HO2S) in the exhaust manifold measures the amount of oxygen in the exhaust gas, which is in indication of combustion efficiency, and sends a signal to the PCM.

The sixth signal, camshaft position information, is transmitted by the CMP sensor, installed in place of the distributor (engines with distributorless ignition), or integral with the distributor.


MAF TESTING With the engine running at idle, use a DVOM to verify there is at least 10.5 volts between terminals A and B of the MAF sensor connector. This indicates the power input to the sensor is correct. Then, measure the voltage between MAF sensor connector terminals C and D. If the reading is approximately 0.34–1.96 volts, the sensor is functioning properly.

MAF sensor


MAF Sensor




Turn the ignition switch OFF.
Disengage the wiring harness connector from the IAT sensor
1.Using a Digital Volt-Ohmmeter (DVOM), measure the resistance between the two sensor terminals.
2. Compare the resistance reading with the accompanying chart.
If the reading for a given temperature is approximately that shown in the table, the IAT sensor is okay.
3. Attach the wiring harness connector to the sensor.


IAT Sensor

IAT Sensor




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This post was written by admin on July 2, 2010

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