Installed options matrix table and platform code in the LS1 PCM

[TheMechanic]

Already has latest calibrations in everything. It's a common/'normal' issue at least on these trucks.

With this weird front sump pan, if the oil level isn't 1/2qt overfilled a hard launch will make it gulp air - I've seen it as low as 20psi in the scanner while the gauge never moved. And cold it's 50psi but gauge still sits rock-solid on 40.

To bad they don't make a table similar to the fuel gauge that you can calibrate output to make the gauge more reflective of reality.
Maybe a dropping resistor or voltage divider. I know I have pulled the cluster lens and popped off the voltmeter needle with a fork and "realigned" it to a more accurate display.

[blindsquirrel]

It's not the gauge or the IPC, something about the data it gets from the ECM makes it work like an indicator instead of a real gauge. The gauge sweeps just fine in bidirectional controls.

Engine Oil Pressure Gage

The instrument panel cluster (IPC) displays the engine oil pressure as determined by the engine control module (ECM). The IPC receives a serial data message from the ECM indicating the engine oil pressure. The engine oil pressure gage defaults to 0 psi (0 kPa) or below if:
• The ECM detects a malfunction in the engine oil pressure sensor circuit.
• The IPC detects a loss of serial data communications with the ECM.

For the 4.2L LL8, the ECM uses an engine oil switch that is open when the oil pressure is normal and closed when the oil pressure is low. At normal pressure, the engine oil pressure gage will display 275 kPa (40 psi). At low pressure, the gage will go to 0 kPa and the low pressure warning will be displayed in the driver information center (DIC). At high pressure, the gage will display 551 kPa (80 psi). Any values between these three values are calculated values determined by the ECM.

Odd that they single out the LL8 with a switch instead of sensor, because the V8 with a real 3-wire sensor behaves exactly the same.