Oil pressure/coolant temperature gauge not working

  • 180,000 MILES
So I changed my plugs and plug wires. Upon starting it the oil gauge now shoots to 80 psi and then drops to zero like it is not working at all. Sometimes it shoots back up to 80 but there is no fluctuation like there would be if it was working. Also, the temperature gauge now refuses to go up. It stays on the cold side and will not rise. Also, immediately the check engine light came on with a p0641 code. 5 volt reference one circuit malfunction. I do not see any sensors I could of knocked loose. I did forget to plug a wire into coil one and it sparked when I started it. But I have heard of people doing that just to test for spark. Could that of shorted something?
Do you
have the same problem?
Tuesday, June 26th, 2018 AT 4:12 PM

1 Reply

Hi and thanks for using 2CarPros. Com.
I have to be honest, it is easy to move or disconnect either of those two sensors. I am going to give you the directions for removal and replacement. Look over the directions and check wiring to the switch to see if something was damaged, disconnected, loose.

Here is the oil pressure switch:

2003 Chevy Truck K Tahoe 4WD V8-5.3L VIN T
Vehicle Engine, Cooling and Exhaust Engine Oil Pressure Sensor Service and Repair
Engine Oil Pressure Sensor and/or Switch Replacement
Tools Required
J41712 0il Pressure Switch Socket
Removal Procedure
If necessary, remove the engine sight shield.
Disconnect the oil pressure sensor electrical connector (1).
Using J41712 or equivalent, remove the oil pressure sensor.
Installation Procedure
Apply sealant GM P/N 12346004, (Canadian P/N 10953480), or equivalent, to the threads of the oil pressure sensor.
Notice: Refer to Fastener Notice in Service Precautions.
See: Service PrecautionsVehicle Damage WarningsFastener Notice
Using J41712 or equivalent, install the oil pressure sensor. Tighten the oil pressure sensor to 35 Nm (26 ft. Lbs.).
Connect the oil pressure sensor electrical connector (1).
If necessary, install the engine sight shield.


The forth picture is the location of the coolant temperature sensor. You can see how changing plugs can disturb it. Check that, too.

Let me know if this helps or if you have other questions.

Take care,
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Wednesday, June 27th, 2018 AT 6:57 PM

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