Diagnostic Aids

WARNING: This page is about a different car, the 2003 Ford Pickup, 2003 Ford F550 Super Duty, 2003 Ford F450 Super Duty, 2003 Ford Excursion, and 2003 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.

The Camshaft Position (CMP) signal source is a magnetic pickup sensor mounted on the left front side of the engine block. The sensor reacts to a peg on a target wheel that is positioned on the camshaft. The peg will pass the sensor once per camshaft revolution and produce a single pulse correspondingly. Camshaft speed is calculated from the frequency of the CMP sensor signal. Diagnostic information on the CMP input signal is obtained by performing accuracy checks on signal levels, frequency and duty cycle with software strategies. The Powertrain Control Module (PCM) needs the Crankshaft Position (CKP) sensor and CMP signal to calculate engine speed and position. The CMP creates a signal that the PCM uses to indicate a particular bank. The CMP sensor contains a permanent magnet that creates a magnetic field. The signal is created when the camshaft peg rotates past the sensor breaking the magnetic field. The PCM conditions the CMP signal and sends it out as a TACH signal for body builder use. The engine will not operate without a CMP signal.

Engine Speed

Is determined by counting the 12 windows on the cam gear each camshaft revolution.

Fuel Timing Control

The position of cylinders No. 1 and No. 4 is determined by distinguishing a narrow or wide window on the camshaft gear.

Engine Mode Selection

Allows the PCM to discern when the engine is in the off, crank or run mode.

Injection Control Pressure

Engine speed is one of the controlling variables in the calculation of desired injection control pressure.

Exhaust Back Pressure

Exhaust back pressure control is a function of engine speed and load.

Fuel Quantity Control/Torque Limiting

Engine torque and fuel is controlled and is dependent on engine speed. Fuel quantity is determined by engine speed.

Detection/Management

An inactive CMP signal during cranking is detectable by the PCM. An inactive CMP signal will cause a no-start condition. Electrical noise can also be detected by the PCM. If the level is sufficient to affect engine operation, a corresponding DTC will be set. Perform this test when directed by QUICK TEST. This test is only intended to diagnose the following components and circuits:
- Camshaft Position (CMP) Sensor
- Wiring Harness Circuits; (CMP, CMP GND & VREF)
- Powertrain Control Module (PCM)

Fig 1: Identifying CMP Sensor Connector Terminals

Courtesy of FORD MOTOR CO.