Chart C-16A Fuel Pump and Engine Oil Pressure Switch Input

Chart C-16A Fuel Pump And Engine Oil Pressure Switch Input:

Fuel Pump And Engine Oil Pressure Switch Input:

CIRCUIT DESCRIPTION
The fuel pump and engine oil pressure indicator switch has two functions, to indicate low engine oil pressure and to supply battery voltage to the fuel pump in the event the fuel pump relay fails.

The oil pressure portion of the switch has normally closed contacts that open on an increasing oil pressure of 41.37 kPa (6 psi) or less, and close on a decreasing pressure of 13.79 kPa (2 psi). when the switch is closed, the oil pressure signal is sent to the Powertrain Control Module (PCM), which in turn sends the information to the instrument cluster (IPC) through serial data. The oil pressure symbol on the instrument cluster is then illuminated.

The fuel pump portion of the switch has normally open contacts that close on an increasing oil pressure of 41.37 kPa (6 psi) or less, and open on a decreasing pressure of 13.79 kPa (2 psi). In the event the fuel pump relay fails, battery voltage is supplied to the fuel pump through the closed contacts.

CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.

1. The PCM senses when the oil pressure signal is pulled low by the oil pressure switch. This step will determine if the PCM is able to sense the signal.
2. The PCM uses a voltage signal to sense when the oil pressure circuit is pulled low. This step will determine if battery voltage was on this circuit normally or because of a short.
3. When oil pressure is low, the signal circuit is grounded through the oil pressure switch. This step will determine if the signal is grounded because of the oil pressure switch or a short to ground.
4. When the signal circuit is probed with a test light to ground, the oil pressure symbol will illuminate. This will determine whether the IPC or oil pressure switch is at fault.

DIAGNOSTIC AIDS
^ Low oil level or low oil pressure at times may be caused by an engine mechanical problem. If a low oil pressure problem is suspected, check engine oil pressure.
^ An intermittent problem may be caused by a poor connection, rubbed through wire insulation, or a wire that is broken inside the insulation.
^ Any circuitry, that is suspected as causing the intermittent complaint, should be thoroughly checked for improper mating, broken locks, poor terminal to wiring connections or physical damage to the wiring harness.