Power grounds. Power steering pressure switch- pcm input

Power grounds

OPERATION

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. Sensor return is a lownoise, low-current, dedicated 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

DESCRIPTION

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 4.7L V-8 engine and power steering.

Fig. 2 Power Steering Pump Pressure Switch-4.7L V-8 Engine

1 - HYDRAULIC PUMP

2 - POWER STEERING PRESSURE SWITCH

3 - RACK AND PINION GEAR

4 - OIL COOLER

OPERATION

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 +- 690 kPa (475 psi +- 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.