E040

Code E040 - Power Steering Pressure Switch Circuit Open:

Wiring Diagram for Code E040 - Open Power Steering Pressure Circuit:

CODE E040 - OPEN POWER STEERING PRESSURE CIRCUIT

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 opens and a "low" voltage is monitored at ECM Terminal "D11". 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 E040 the following conditions must be met:

a. Open power steering switch.
b. Vehicle speed is greater than 50 MPH.
c. Both conditions existing for a time greater than 12.8 seconds.




Test Description: The following numbered steps correspond with the step numbers on the diagnostic chart.

1. Tests the power steering pressure switch for proper operation by using the "self-diagnostics" system. "LO" 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 "HI", if the circuit is complete. If so, the power steering pressure switch or connection is faulty.

3. If the display switches to "HI" when 12 volts is jumpered to CKT 495, the fault is an open in CKT 50.




Diagnostic Aids:

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

Check For:

a. Poor Connection or Damaged Harness - Inspect ECM harness connectors for backed out terminal "D11", improper mating, broken locks improperly formed or damage terminals, poor terminal to wire connection and damaged harness.

b. Intermittent Test - If connections and harness checks out ok, monitor E178 (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 will help to isolate the location of the malfunction.