Can anyone point me at a wiring diagram?

 

Just buy an oil sensor for an 02. 01 is different voltage

 

You think just swapping senders would do it? I figured the wiring was different also. When I unplugged the connector with the motor running the gauge didn't move at all, still pointing at 3 o-clock. So maybe the center wire on the 3 wire connector is the one that comes out from the gauge and it will work?

I'll give it a shot, I was already planning on getting the correct sender.

 

Further research indicates this will not work. The 03 and newer senders operate at a different voltage range and send to the computer first, and then to the gauge. The 02 sender goes straight to the gauge.

Still looking for a wiring diagram of the instrument connector or the main connector in the engine bay for a 2002.

 

Here is the wiring diagram for the instrument cluster in an 02. Wire is tan with a white stripe and comes from the sending unit and goes to C100, from C100 it passes through the firewall and goes straight up to the instrument cluster Pin A1. The sending unit is a variable resistance type sending unit.

The 03 up sender is a variable voltage type sending unit. It has a 5V reference voltage and a sensor ground. Depending on the change of resistance in the sending unit, the voltage going back to the PCM changes. Unfortunately, they are not interchangeable.

In your case, figure out which wire goes to pin A1 on the instrument cluster (if any...) If all three wires go back to the PCM, then just run a new wire down from the instrument cluster to your single wire sending unit.

 

Thats what I was looking for! I'm going to try to get to it this weekend, I'll post up the results.

Thanks 80Sierra

 

Sorry, read op wrong. Good luck

 

Dash cluster for LB7's

There isn't likely anything wrong with your oil pressure! On the LB7's ( I do believe) have a special warranty on the dash cluster. You pay for the labour and they pay for the dash cluster. On mine when I bought the truck the temp gauge always read above the bottom line, last Dec the volt gauge started reading around to the 5 o-clock position then 3 weeks ago the speedo would read all over 160 km's doing 2100 rpm mornings with I went out to start it it was going 45 km's an hour. So got it replaced and has been good since.

 

My fix

Oil pressure gauge is now functional! This is definitely not an 02 engine harness, but everything seems to work now, so I'm gonna go with it.

Here was the problem;
This is the wire coming from the oil pressure gauge that is supposed to connect to the sender.

Here is the harness on the motor. Notice no pin for the oil pressure to connect to.

I'm guessing this is the difference in a 02 and later vs. an 03 and newer.

So the solution is to get the correct 02 oil pressure sender and connect to the light tan with wite stripe wire coming out of the cluster. I forgot to take a picture of the cluster connector, but it was a corner location.

Since the sender harness on the motor wasn't doing me any good, a clipped a wire there and soldered to my new connector. You'll need AC Delco part # PT100 and a correct 02 oil pressure sender and some wire.

 

Oil Pressure Gauge / Sending Unit Wiring- 2002 Duramax LB7 replaced with a 2003 LB7

I have a 2002 Silverado 2500hd with a 2002 wiring harness (truck side) connected to a newer 2003 LB7 engine with a 2003 wiring harness (engine side). As discovered and documented by Flyingsquirel above, I had the same problem with the oil pressure sending unit.
Initially, I thought it was the sending unit or the gauge cluster. I replaced the (single wire) 2002 oil pressure sending unit with no change. I pulled the cluster apart to check with no luck determining any problems. I purchased a ScanGauge II, which will digitally display the dashboard gauges, and didn’t get any readings on the oil pressure, but was able to verify other readings on my gauge cluster and check for diagnostic codes. The gauge cluster has never displayed any “oil” warnings, even with the oil pressure sending unit disconnected and the engine running.
I came across this thread, which has been quite helpful….THANKS!!! Following the “fix” as described in the thread, I also disconnected the gray/white wire from the oil pressure sending unit (capped it off) and temporarily installed a new wire connecting from the sending unit to the truck’s side of the harness (on the gray/white wire, [rather than all the way to the gauge cluster]). The oil pressure needle engaged and moved counterclockwise from its former (inactive) position at 11 o’clock to about 5 o’clock (off the chart). The ScanGauge II did not display any readings for oil pressure.
The Problem/inquiry:
I need to know if the oil pressure gauge should normally move counterclockwise and what some “normal” readings/behaviors look like (including from when the key is activated without the engine running through cold start, etc..). I’m thinking that I need to make an adjustment to the gauge in the cluster, but I'm not sure how to proceed. According to the schematic, it doesn’t look like the gray/white wire on the engine’s side needs to be connected to the sending unit (with the new wire now in place), any thoughts? I don’t understand why the Powertrain Control Module (PCM) and/or Engine Control Module (ECM) are not reporting oil pressure to the ScanGauge or why there have never been any “oil” warnings on the gauge cluster either before or after the new wire and connection were completed. Thanks in advance for your advice.