Oil Pressure Switch

Diagnostic Chart:

Wiring Diagram:

^ The following tables will diagnose the oil pressure switch and the coolant level switch circuits.

^ For Diagnosis of the Instrument Panel Cluster refer to Instrument Panel.

^ For PCM replacement information. Refer to PCM/EEPROM Replacement/Programming.

Circuit Description

The engine oil pressure indicator switch indicates low engine oil pressure. The oil pressure indicator switch has normally closed contacts that open when oil pressure is greater than 41 kPa (6 psi). The contacts will close when oil pressure is less than 14 kPa (2 psi). When the contacts are closed, the oil pressure signal is sent to the Powertrain Control Module (PCM). The PCM then sends this signal to the Instrument Panel Cluster (IPC) through to illuminate the oil pressure telltale lamp on the IPC.

Diagnostic Aids

^ Low oil level or low oil pressure at times may be caused by an engine mechanical problem.

^ 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 the following conditions:

- Backed out terminals

- Improper mating

- Broken locks

- Damage to the wiring harness

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the scan tool for later reference.

2. This step is crucial to prevent possible engine damage due to a low oil condition.

7. 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.

8. When the 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.

9. 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. When the signal circuit is probed by a test light connected to ground, the oil pressure symbol will illuminate.

15. If an oil pressure problem is suspected, do not run the engine longer than necessary to avoid possible internal engine damage.

16. For Diagnosis of the Instrument Panel Cluster refer to Instrument Panel.

19. Reprogram the replacement PCM. Perform the crankshaft position system variation procedure. Refer to the latest Techline procedures for PCM reprogramming and the Crankshaft Position System Variation Procedure. Refer to Powertrain Control Module.

20. If no malfunctions have been found at this point, refer to Diagnostic Aids for additional checks and information.