Engine Sensors & Control

ICP Sensor

The injection control pressure (ICP) sensor is a variable capacitance sensor that, when supplied with a 5-volt reference signal from the powertrain control module (PCM), produces a linear analog voltage signal that indicates pressure.

The ICP sensor's primary function is to provide a feedback signal to indicate rail pressure so that the PCM can command the correct injector timing and pulse width and the correct injection control pressure for proper fuel delivery at all speed and load conditions.

Detection/Management

If the PCM detects a malfunctioning ICP sensor (sensor out of range high or low), the CHECK ENGINE light is illuminated and the PCM will go to open loop control of injection control pressure. (Operate from an estimated injection control pressure.)

Accelerator Pedal

Signal Functions

The accelerator pedal (AP) sensor provides the powertrain control module (PCM) with the driver's demand for power.

The AP signal is used in calculating desired fuel quantity, injection timing and injection control pressure.

Fault Detection/Management

Any detected malfunction of the AP sensor will illuminate the CHECK ENGINE light.

An AP signal that is detected out of range high or low by the PCM will cause the engine to ignore the AP signal and will only allow the engine to operate at low idle.

If a disagreement in the state of idle validation switch (IVS) and AP sensor is detected by the PCM, the engine will only be allowed to operate at low idle.

Camshaft Position Sensor

Signal Functions

The camshaft position (CMP) sensor is a Hall-effect type sensor that generates a digital frequency, as windows in a target wheel pass through its magnetic field. The frequency of the windows passing by the sensor as well as the width of selected windows allows the powertrain control module (PCM) to detect engine speed and position.

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 effect engine operation, a corresponding DTC will be set.

Signal Functions

The manifold absolute pressure (MAP) sensor is a variable capacitance sensor that, when supplied with a 5-volt reference signal from the powertrain control module (PCM), produces an analog voltage signal that indicates pressure.

Smoke Control — The MAP signal is used to control smoke by limiting fuel quantity during acceleration until a specified boost pressure is obtained.

Dynamic Injection Timing — Optimizes injection timing for boost pressure measured.

Fault Detection/Management

A MAP signal that is detected by the PCM to be out of range or at an incorrect value for specific conditions will cause the PCM to ignore the MAP signal and operate the engine from an inferred boost pressure signal.

Note

After removing connectors, always check for damaged pins, corrosion, loose terminals, etc.

Note: ± 0.3 volt from expected voltage reading is allowed.

Injection Pressure Regulator (IPR)

Output Functions

Injection Pressure Regulator (IPR) — A variable position valve that controls injection control pressure. The powertrain control module (PCM) uses many input variables to determine the desired injection control pressure.

Battery voltage is supplied to the IPR when the ignition key is in the ON position. Valve position is controlled by switching the output signal circuit to ground inside the PCM. ON/OFF time is modulated from 0 to 50% dependent upon the desired injection control pressure.

Detection/Management

An open or shorted to ground control circuit can be detected by an on demand output circuit check performed during the KOEO test. When the starter is engaged and the engine fails to start, the IPR command will increase toward its maximum until the engine starts. The normal range for the IPR at idle is between 8-16%. An above 16% range indicates high effort to achieve idle. A below 8% indicates low effort to achieve idle.

The PCM is capable of detecting whether desired injection control pressure is equal to measured injection control pressure while the engine is running. If the measured injection control pressure does not reasonably compare to the desired injection control pressure the PCM ignores the measured ICP sensor signal and attempts to control the engine with the desired value. (If the problem was in the sensor circuit this strategy causes little performance deterioration. If the problem is in the control circuit, engine performance will probably still be unsatisfactory).

An injection control pressure step test, in which the PCM commands and then measures specific preprogrammed pressures is performed during the KOER test.

The engine will not operate with an IPR circuit that is not functioning.

DTC Descriptions

P1209 = ICP system fault

P1211 = If set during normal engine operation, indicates engine is operating in open loop control and injection control pressure is above or below desired pressure. If set during KOER test, indicates ICP system failed step test and could not maintain commanded pressure.

P1282 = Injection control pressure was greater than 3675 psi for 1.5 seconds (possible grounded IPR control circuit). Refer to injection control pressure diagnostics if not electronic concern.

P1283 = Output circuit check detected during KOEO test; indicates high or low resistance in circuit.

Air Intake Temperature Sensor

Signal Functions

The intake air temperature (IAT) sensor is a thermistor-type sensor with a variable resistance that changes when exposed to different temperatures. When interfaced with the powertrain control module (PCM), it produces a 0-5 volt analog signal that will measure temperature.

The IAT sensor's primary function is to measure ambient air temperature in order to determine when the exhaust back pressure device is needed. It is also used as input to determine idle kicker function.

Detection/Management

An IAT signal that is detected out of range high or low by the PCM will cause the engine to ignore the IAT signal, disable exhaust back pressure operation and assume an ambient temperature of 15°C (59°F).

DTC Descriptions

P0113 = Intake Air Temperature Sensor circuit High Input.

P0112 = Intake Air Temperature Sensor circuit Low Input.

Engine Oil Temperature Sensor

Signal Functions

The engine oil temperature (EOT) sensor is a thermistor type sensor that has a variable resistance that changes when exposed to different temperatures. When interfaced with the powertrain control module (PCM), it produces a 0 to 5 volt analog signal that will deduce temperature.

Cranking Fuel Quantity/Timing Control — The EOT sensor signal is used to determine the timing and quantity of fuel required to optimize starting over all temperature conditions.

Idle Speed — At oil temperatures below 70°C (158°F) low idle is incrementally increased to a maximum of 950 rpm.

Temperature Compensation — Fuel quantity and timing is controlled throughout the total operating range to ensure adequate torque and power is available.

Glow Plug Control — The glow plug relay (federal) or Glow Plug Control Module (GPCM) (California) and lamp ON times are controlled by engine oil temperature.

Detection/Management

An EOT sensor signal that is detected out of range (high or low) by the PCM will cause the PCM to ignore the EOT sensor signal and assume an engine oil temperature of -20°C (-4°F) for starting and a temperature of 100°C (212°F) for engine-running conditions. The CHECK ENGINE light will also be illuminated as long as the condition exists.