Power Steering Pressure Switch-PCM Input

Fig. 9 Power Steering Pump Pressure Switch:

OPERATION
A pressure sensing switch is included in the power steering system (mounted on the high-pressure line). This switch will be on vehicles equipped with power steering. The switch (Fig. 9) 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 1896 kPa +/- 345 kPa (275 psi +/- 50 psi), the normally closed switch will open and the PCM will increase the engine idle speed. This will prevent the engine from stalling.

When steering pump pressure drops below approximately 70 psi, the switch circuit will close and engine idle speed will return to its previous setting.

CIRCUIT OPERATION
The Powertrain Control Module (PCM) connects to the power steering pressure switch on circuit K10. On vehicles equipped with a manual transmission, circuit Z12 provides ground for the switch. If the vehicle has an automatic transmission, circuit Z1 provides ground. When the switch closes, it connects circuit K10 to ground. The switch closes during periods of high power steering pump load and low engine speed; such as parking maneuvers.

Circuit K10 connects to cavity A12 of the PCM. Circuit Z12 also connects to cavities A31 and A32 of the PCM.