Jeep Cherokee (XJ): Power grounds. Power steering pressure switch- pcm input. Sensor return-pcm input

Jeep Cherokee (XJ) 1984 - 2001 Service Manual > Fuel system > Fuel injection system > Description and operation > Power grounds. Power steering pressure switch- pcm input. Sensor return-pcm input

Power grounds


The Powertrain Control Module (PCM) has 2 main grounds. Both of these grounds are referred to as power grounds. All of the high-current, noisy, electrical devices are connected to these grounds as well as all of the sensor returns. The sensor return comes into the sensor return circuit, passes through noise suppression, and is then connected to the power ground.

The power ground is used to control ground circuits for the following PCM loads:

  •  Generator field winding
  •  Fuel injectors
  •  Ignition coil(s)
  •  Certain relays/solenoids
  •  Certain sensors

Power steering pressure switch- pcm input


A pressure sensing switch (Fig. 2) is included in the power steering system (mounted on the highpressure line). This switch will be used only on vehicles equipped with a 2.5L engine and power steering.

Fig. 2 Power Steering Pump Pressure Switch-2.5L Engine
Fig. 2 Power Steering Pump Pressure Switch-2.5L Engine



The power steering pressure switch provides an input to the Powertrain Control Module (PCM). This input is provided during periods of high pump load and low engine rpm; such as during parking maneuvers.

The PCM will then increase the idle speed through the Idle Air Control (IAC) motor. This is done to prevent the engine from stalling under the increased load.

When steering pump pressure exceeds 3275 kPa 6 690 kPa (475 psi 6 100 psi), the normally closed switch will open and the PCM will increase the engine idle speed. This will prevent the engine from stalling.

When pump pressure drops to approximately 1379 kPa (200 psi), the switch circuit will re-close and engine idle speed will return to its previous setting.

Sensor return-pcm input


The Sensor Return circuits are internal to the Powertrain Control Module (PCM).

Sensor Return provides a low-noise ground reference for all engine control system sensors. Refer to Power Grounds for more information.

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