C7 Industrial Engine Operation and Maintenance Manual – Sensors and Electrical Components | Caterpillar Engines Troubleshooting (2024)

Sensor Locations
Illustration 1 shows the typical locations of the sensors for a C7 Industrial Engine. Specific engines may appear different from the illustration due to differences in applications.

Left side view

(1) Injection actuation pressure sensor

(2) Inlet air temperature sensor

(3) Atmospheric pressure sensor

(4) Boost pressure sensor

(5) Engine oil temperature sensor

(6) Engine speed/timing sensor

(7) Coolant temperature sensor

(8) Engine oil pressure sensor

Failure of Sensors

All Sensors
A failure of any of the sensors may be caused by one of the following malfunctions:

Sensor output is open.
Sensor output is shorted to “- battery” or “+ battery”.
Measured reading of the sensor is out of the specification.

Atmospheric Pressure Sensor
Atmospheric pressure sensor (3) measures the atmospheric pressure in the crankcase. A signal is sent to the Electronic Control Module (ECM).

Boost Pressure Sensor
Boost pressure sensor (4) provides a signal which corresponds to turbocharger outlet pressure to the ECM. The air/fuel ratio control utilizes the actual engine speed and the turbocharger outlet pressure in order to control the transient smoke level. The ECM can control injection timing and the amount of fuel that is injected. When the throttle is increased and when the engine demands more fuel, the fuel limit is controlled in order to reduce overall smoke levels of the engine exhaust.

Failure of the Boost Pressure Sensor
The ECM will detect failure of the boost pressure sensor. The operator will be warned of the problem through the diagnostic lamp. The strategies that are related to the boost will be disabled. Engine power will be severely reduced in the event of a failure of the boost pressure sensor. A failure of the boost pressure sensor will not cause a shutdown of the engine.

Coolant Temperature Sensor
Coolant temperature sensor (7) monitors engine coolant temperature. The output of the ECM can indicate a high coolant temperature through a relay or a lamp. The coolant temperature sensor is used by the ECM to determine initiation of the Cold Start Strategy.

Failure of the Coolant Temperature Sensor
The ECM will detect a failure of the coolant temperature sensor. The diagnostic lamp will warn the operator about the status of the coolant temperature sensor. A failure of the coolant temperature sensor will not cause a shutdown of the engine or any horsepower change.

Engine Oil Pressure Sensor
Engine oil pressure sensor (8) is an absolute pressure sensor that measures the engine oil pressure in the main oil gallery. The engine oil pressure sensor detects engine oil pressure for diagnostic purposes. The engine oil pressure sensor sends a signal to the ECM.

Low Oil Pressure Warning
The setpoint is dependent upon the engine speed. The fault will be active and logged only if the engine has been running for more than 15 seconds.

Very Low Oil Pressure Warning
The very low oil pressure setpoint is dependent upon the engine speed. If the DERATE mode of the engine monitoring system is selected, the ECM will derate the engine power. The engine horsepower will be limited.

Failure of the Engine Oil Pressure Sensor
The ECM will detect failure of the engine oil pressure sensor. The diagnostic lamp warns the user about the status of the engine oil pressure sensor. The engine oil pressure related strategies will be disabled in the event of a failure of the engine oil pressure sensor. A failure of the engine oil pressure sensor will not cause a shutdown of the engine or any horsepower change.

Engine Oil Temperature Sensor
Engine oil temperature sensor (5) monitors the temperature of the engine oil. The ECM uses the information from the engine oil temperature sensor in order to adjust the timing of the fuel injection and the pressure of the fuel injection.

Engine Speed/Timing Sensor
If the ECM does not receive a signal from primary speed/timing sensor (6), the “DIAGNOSTIC” lamp will indicate a diagnostic fault code which will be logged in the ECM memory.

If the ECM does not receive a signal from the primary speed/timing sensor, the ECM will read the signal from the secondary speed/timing sensor. The ECM continually checks in order to determine if there is a signal from both sensors. If either sensor fails, the faulty sensor should be replaced.

Intermittent failure of the sensors will cause erratic engine control.

Injection Actuation Pressure Sensor
Injection actuation pressure sensor (1) provides a signal of the injection actuation pressure to the ECM. The ECM modifies the current to the injection actuation pressure control valve (not shown) in order to control the injection actuation pressure. The desired actuation pressure is based on the following engine parameters: quantity of fuel, injection timing, engine speed and engine operating mode.

Inlet Air Temperature Sensor
Inlet air temperature sensor (2) measures the inlet air temperature. A signal is sent to the Electronic Control Module (ECM). The inlet air temperature sensor is also used by the ECM to determine initiation of the Cold Start Strategy.

Throttle Position Sensor
The Throttle Position Sensor (TPS) sends a signal to the ECM. The signal from the TPS is required in order to govern engine speed. The throttle position sensor signal is used by the ECM in order to calculate the desired engine speed. The TPS is calibrated during the initial installation of the engine.

Note: The throttle position sensor is not shown in the illustration.

Failure of the Throttle Position Sensor
An intermittent failure in the TPS causes the engine speed to vary erratically. The ECM will perform the following process:

The ECM will detect the failure of the TPS.
The ECM will warn the operator of the failure through the diagnostic lamp.
The ECM will set the desired engine speed to low idle.