What is causing my 1999 C5 to have a high oil temperature and reduce engine RPM warnings when the car hasn't ran long enough to warm up the oil? Where is the sensor located and can I change it out without going through the dealer? Funny thing is I can get a high oil temp and a minute later get a low oil temp warning...could it be the module? The car seems to fall into a limp mode when it happens. Sometimes I can shut it down and crank it back up with success..other times it's an embarrassing ride home having to pull over numerous times..

 

Run your codes and post them:

To enter the Diagnostic Display function perform the following steps in order:
1. Turn ON the ignition switch, engine OFF.
2. Press the RESET button to acknowledge any warning messages present.
3. Press the OPTIONS button on the Driver Information Center (DIC) and hold.
4. While holding the OPTIONS button press the FUEL button 4 times within a 10 second period.
5. System will first enter automatic display mode followed by the manual display mode.

The automatic display feature allow you to read each module DTC display function in an automatic display sequence. Each system module DTC will be displayed for 3 seconds followed by a 1 second pause before the next DTC is displayed in an automatic sequence. If no DTC information is sent to the IPC from the system currently displayed on the IPC, the IPC will display NO CODES for that system. At any time during the automatic display function, the manual display feature can be activated by pressing any button on the DIC except the E/M 5 button. The E/M 5 button is used to completely exit the DIAGNOSTICS mode at any time. If there is a communications problem between any system, the IPC will display NO COMM when the IPC is trying to communicate with that system. When all DTCs have been displayed for all systems, the IPC will display NO MORE CODES for 2 seconds then will enter the manual display mode, waiting for manual mode operation.

The manual display feature allows you to manually select each module DTC display function. The manual mode will automatically be entered after the automatic DTC display sequence is complete, or can be entered at any time during the automatic mode by pressing any button on the DIC except the E/M 5 (E/M 5 button is used to exit the DIAGNOSTIC mode at any time). When the manual mode is selected, the IPC will display the MANUAL DIAGNOSTICS mode message for 2 seconds, or until any button on the DIC except the E/M 5 is pressed. After the MANUAL DIAGNOSTICS mode message is displayed, the IPC will display the first system abbreviation and quantity of codes stored for that system, then the IPC will wait for further instructions. The buttons on the DIC provide the following functions when operating the on-board diagnostic feature in the manual mode:

DIC Button Function
FUEL 1 Previous DTC
GAGES 2 Next DTC
TRIP 3 Previous System
OPTIONS 4 Next System
E/M 5 Exit Diagnostics
RESET Clear DTCs

 

Cleared all of the codes and ran the car...

Codes that return: B1542 and B1543

I've exchange what I believed to be the oil temp sensor that I found located at the oil filter with another used one from the same year motor and still same codes...

Thanks for spending your Easter trying to help me!

 

I should mention the check engine light is not coming on....

 

Here's a couple quick things to try:

Check if the IPC is able to recognize a change in resistance from the oil temperature sensor by disconnecting the oil temperature sensor. If the IPC oil temperature display changes from HIGH temperature (above 190°C [200°F]) with sensor connected, to LOW temperature (-10°C [14°F]) with the sensor disconnected. Then the IPC and CKT 357 is not cause of the malfunction and the oil temperature sensor must be checked.

At the oil temperature sensor connector (harness side), measure the voltage between terminal B and ground.Was the voltage indicated between the specified value? 4.5-5.5 Volts

 

Terminal B is the green/white wire.

 

Thanks so much.. I'm going to check the volts in the morning... BUT, when we first started this morning we disconnected the oil sensor and tried to run the motor after it was disconnected...immediate engine failure. Never had that happen so we change the units out, that's where I'm at with it. It's a daily driver, pretty reliable up until this point. We live on a dirt road that is horrible, so I'm trying to check all of the grounds. The battery is reading 12.2 with the key on, and 13.2 running...that's not an issue, right?

 

Shouldn't be an issue. While you are checking for voltage at terminal B check for continuity to ground at terminal A (the black wire).

 

Thanks, will do.