Keep in mind that the engine oil pressure may be low, oil pressure switch may be faulty, or the oil temperature sensor may not be working correctly. Since the main crank bearings make the oil pressure there may be something internally wrong with the engine. If there is excessive clearance in the main bearings the oil pressure will be low. I would suggest performing a test on the oil pressure switch and the oil temp sensor. If they check out good then It wouldn't hurt to put a mechanical oil pressure gauge on the engine.
As for the code p0884 here is some information. This code might be related to the random vehicle shut offs. It has something to do with the ignition power to the PCM/TCM.
Theory of Operation
If a vehicle loses power to the Transmission Control System, the solenoids (L/R, 2C, OD, UD, 4C) will go to their respective power off state. Some solenoids are normally vented and some are normally applied in their power off state. The transmission is designed to be in 3rd gear with all of the solenoids in this state. However, if power is restored, the Transmission Control System will power-up and normal operation will be restored.
This code identifies that power to the Transmission Control System was restored when the gear selector was in a "Drive" position while the vehicle was moving at speeds above 32 Km/h (20 mph). This DTC does not indicate a problem with the transmission or Transmission Control System, instead, it suggests intermittent problems in the fused ignition switch output, fused B(+), or ground circuits to the TCM. Alternately, if a person performs a rolling restart maneuver, the DTC can be set. Therefore it is critical that this DTC be investigated if the vehicle is experiencing intermittent 3rd gear operation and a subsequent return to normal operation.
When Monitored:
When Powertrain Control Module initially powers up. Due to the integration of the Powertrain and Transmission Control Modules, the transmission part of the PCM has its own specific power and ground circuits.
Set Condition:
This DTC will set if the PCM powers up and senses the vehicle in a valid forward gear, with no PRNDL DTCs, and an output speed above 800 RPM, approximately 32 Km/h (20 mph) .
Always perform the 45RFE/545RFE Pre-Diagnostic Troubleshooting Procedure before proceeding. See: Powertrain Management\Transmission Control Systems\Testing and Inspection\45RFE/545RFE Pre-Diagnostic Troubleshooting Procedure
Diagnostic Test
1. CHECK THE POWER AND GROUND CIRCUITS
This DTC is set when the Transmission portion of the Powertrain Control Module is initialized while the vehicle is moving down the road in a valid forward gear.
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors.
NOTE: Due to the integration of the Powertrain and Transmission Control Modules, the transmission part of the PCM has its own specific power and ground circuits.
Check all of the Fused B(+), Fused Ignition Switch Output, and ground circuits to the PCM for an intermittent open or short to ground.
With the scan tool, check the DTC EVENT DATA to help identify the conditions in which the DTC was set.
If there are no possible causes remaining, view repair.
Repair
Check all power and ground circuits to the PCM and repair as necessary.
Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST.
