Oil pressure gage non functioning - 2004 Chevrolet TrailBlazer

Replace the instrument cluster . GM had stepper motor issues 2003 to 2006 . Pin out won't help you , The info for the instrument cluster gauges come's over class 2 serial data buss (network) from the PCM - engine computer . Do you know what GM class 2 data network is ? All gauge info comes over one wire from the PCM .
How to repair GM Instrument Cluster Speedometer Gauge Stepper
Buick Class 2 Operation Diagnosis 1998

Hooking up a Tech 2 scan tool an checking for code's an data to the instrument cluster would be the correct diagnostic procedure . But you wouldn't know that , not being a Chevy technician . Not having factory service repair info. manual .

Speedometer
The IPC displays the vehicle speed based on the information from the PCM. The PCM calculates the vehicle speed from the vehicle speed sensor (VSS) circuit. The IPC receives a class 2 message from the PCM indicating the vehicle speed. The PCM also calculates the vehicle speed based on the wheel reference vehicle speed class 2 message from the EBCM. The PCM uses the vehicle speed information from the EBCM as a backup. The IPC displays the vehicle speed information from the EBCM when the PCM detects a malfunction in the vehicle speed sensor circuit.
The speedometer defaults to 0 km/h (0 mph) if the IPC detects a loss of class 2 communications with both the PCM and the EBCM.

Engine Coolant Temperature (ECT) Gage
The IPC displays the engine coolant temperature on the analog ECT gage as determined by the PCM. The PCM monitors the signal circuit of the engine coolant temperature sensor. The IPC receives a class 2 message from the PCM indicating the engine coolant temperature. The IPC illuminates the check gages indicator when a high engine coolant temperature condition exists. The engine coolant temperature gage defaults to 75°C (160°F) or below when one of the following conditions occur:
• The PCM detects a malfunction in the engine coolant temperature sensor signal circuit.
• The IPC detects a loss of class 2 communication with the PCM.
For additional informatin on the engine cooling system, refer to Cooling System Description and Operation in Engine Cooling.
Engine Oil Pressure (EOP) Gage
The IPC displays the engine oil pressure on the analog EOP gage as determined by the PCM. The PCM monitors the signal circuit of the engine oil pressure sensor. When the engine oil pressure sensor resistance is high, the engine oil pressure is high. When the engine oil pressure sensor resistance is low, the engine oil pressure is low. The IPC receives a class 2 message from the PCM indicating the engine oil pressure. The IPC illuminates the check gages indicator when a low oil pressure condition exists. The engine oil pressure gage defaults to 0 kPa (0 psi) when the following condition occurs:
• The PCM detects a malfunction in the engine oil pressure sensor signal circuit.
• The IPC detects a loss of class 2 communication with the PCM.
Fuel Gage
The IPC displays the fuel level on the analog fuel gage as determined by the PCM. The PCM monitors the signal circuit of the fuel level sensor. When the fuel level sensor resistance is high, the fuel gage indicates full. When the fuel level sensor resistance is low, the fuel gage indicates empty. The IPC receives a class 2 message from the PCM indicating the filtered fuel level percent. The PCM uses 2 filters for the fuel level percent. The slow filter is used during normal operation. The fast filter is used when the engine is just started or when the vehicle is in Park or Neutral. The fast filter allows the fuel gage to reach the current fuel level quickly. The fuel gage defaults to empty when the following conditions occur:
• The PCM detects a malfunction in the fuel level sensor circuit. Refer to Diagnostic System Check - Instrument Cluster .
• The IPC detects a loss of class 2 communications with the PCM.
Reviewing the fuel system description will further explain how the system functions. Refer to:
• Fuel System Description in Engine Controls - 4.3L
• Fuel System Description in Engine Controls - 4.8L, 5.3L, and 6.0L.

NO , there is not a fuse just for those two thing's ! There are two power supply's for the whole insturment cluster . You could need a new cluster or the ECM isn't sending this info. to the cluster . Could have DTC'S - diagnostic trouble codes stored in the PCM or the insturment cluster . Without knowing how this works (insturment cluster gets it's info.) Your best bet , take it to a qualified repair shop that has the knowledge and test equipment to diagnose this problem.
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.

Voltmeter
The instrument panel cluster (IPC) displays the vehicle voltage based on the information from the body control module (BCM). The IPC uses the serial data information from the BCM to provide a voltage level indication on the voltmeter.

DTC P0521: Engine Oil Pressure (EOP) Sensor Performance

DTC P0522 Engine Oil Pressure (EOP) Sensor Circuit Low Voltage
DTC P0523 Engine Oil Pressure (EOP) Sensor Circuit High Voltage

Volt Gage Inaccurate or Inoperative
2
Install a scan tool.
Turn the ignition ON, with the engine OFF.
With the scan tool, perform the instrument panel cluster (IPC) gauges output control.
Does the volt gauge move up and down when commanded?

No damage will occur. Have you checked the oil pressure with a manual test gage? If not do that and please understand GM oil pressure gages are prone to reading high pressure when the sender is defective.

The only way to know if you need engine repair or you have a bad sender is to hook up an oil pressure test gage to the sender port and manually check the pressure. You will need the deep oil pressure sending unit removal tool to get the sender out (I did this).

Oil sending switch needs replaced.

have the oil pressure checked with an independent gage as sometimes gages in the dash don`t show correct pressure. how long has it been since the oil was changed as oil when it gets dirty it thins out and can affect oil pressure. if you don`t hear any ticking with the motor running chances are the pressure is either good or just a little low. testing oil pressure with an independent gage will tell the tale.

you either have a faulty oil pressure switch or you have poor oil pressure.if you find the oil pressure switch remove it and install a manuel oil pressure guage there. then you will see if it is the actual oil pressure weak or if it is the switch.

The "check gages" light comes on in response to the oil pressure (not oil level) gage dropping too low. Step one is to check to make sure the engine has oil pressure. Use a mechanical gage inserted directly into the engine when the oil pressure sensor screws in. If the pressure is good, you need to check the gage. Your dealer has a tool that attaches to the connector from the pressure switch that gose to the gage. He can then test the gage, cluster and circuit wiring. If that is ok the culprit is the oil pressure sensor itself. I normally don't recommend replacing parts without a proper diagnosis but an oil pressure switch is relatively inexpensive. You might want to try that first. It's relatively common anf if that's the culprit, you will save a bunch of $$$ no having to go to your dealer. If you still have a problem, you have at least eliminated one item and are only out a couple of bucks.

One of four things is happening:

1. You are very low on oil, but probably you already checked that

2. The oil pump is not working, but the engine would not last long with no oil circulating.

3 The oil pressure sending unit is defective. This is a unit that send an electrical signal to the gage proportionate to the pressure it is measuring from the engine. If the pressure gage is bad then you get no signal and nothing is measured on the oil pressure gage. Also check the wires from the sending unit to make sure they are not frayed or broken.

4. The oil pressure gage is defective. Yes even new guages can be defective. Check the new gage to make sure is is operating properly. (external voltage check)


The only other possibility is that the engine is loosing lots of oil pressure due to excessive wear.

Good luck

CHECK GAGES light (1) indicates a potential engine failure(low oil pressure, low coolant, coolant overheating) has occurred.
· Check gages and shut down engine. Gages should read as follows: Oil pressure 5 to 10 psi (34 to 69 kPa) at idle; Water Temp gage below 230 degrees (110 C).
· Check engine oil level (Para 2-11) if OIL PRESS gage indicates low reading. Check coolant level (Para 2-11) if Water Temp gage indicates high reading. Notify Unit Maintenance if levels are low.

If CHECK ENGINE light (2) is on, check engine oil pressure gage (3) and water temperature gage (4). If both indicate normal, proceed with mission and then notify Unit Maintenance. If either one does not indicate normal, stop engine immediately and notify Unit Maintenance