Powertrain Controls - ECM/PCM

Code 46 Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION:

The power steering pressure switch is incorporated as an ECM discrete input signal representing the parasitic load placed on the engine during high power steering demand periods, such as parking. This load may cause the engine to stall under high power steering pump pressure conditions, therefore, the ECM compensates by automatically increasing the engine idle speed, via IAC whenever the switch closes and a low voltage is monitored at ECM terminal "BD4." This low voltage indicates a high pressure within the power steering system resulting from high demand. Current is also disrupted to the A/C compressor relay so the A/C clutch is disengaged to further reduce engine load.

To set a Code 46, the following conditions must be met:

^ Closed power steering switch. Power steering signal indicates high pressure (low voltage potential).
^ Vehicle speed is greater than 40 mph.
^ Both conditions existing for a time greater than 25 seconds.

NOTE: Because of all the possible color code combinations used on electrical wiring diagrams, always refer to ECM CONNECTOR IDENTIFICATION under ELECTRICAL AND ELECTRONIC WIRING DIAGRAMS for correct color code identification of circuit.

TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. "Scan" the power steering pressure switch for proper operation. "High" should be displayed when high power steering pressure loads are created.

2. This step determines whether the fault is in the switch or the circuit. A jumpered switch connector should normally indicate "High" if the circuit is complete. If so, the power steering pressure switch or connection is faulty.

3. If the display switches to "High" when CKT 495 is grounded, the fault is an open in CKT 450.

DIAGNOSTIC AIDS:

An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation.

Check for:

Poor connection or damaged harness: Inspect ECM harness connectors for backed out terminal "BD4," improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness.

Intermittent test: If connections and harness check OK, monitor power steering pressure switch display while moving related connectors and wiring harness. If the failure is induced, the power steering pressure switch display will abruptly change. This may help to isolate the location of the malfunction.