1999-02 Cluster Swap 2003-06 Cluster

This guide will focus on a p59 PCM swapped 99-02.
I will start by repining the plug for your stock cluster. The new clusters use the same plug but with a different pin layout. It’s best to repin one wire at a time because GM often uses the same wire color on the same plug. Some wires won't be needed for the new cluster, like the oil pressure switch wire and a few power wires, as the new clusters require only a pink ignition wire and an orange 12V constant wire. I suggest repurposing four of the unnecessary wires to connect to the steering wheel controls for the cluster. Remember to enable the SWC on the cluster for it to function, which can be done by flashing the correct bin file.

After reconnecting the plug, the voltage gauge and oil pressure will likely not work because the 2003 and newer clusters show those readings internally, while the new cluster relies on serial data. The P59 with the 7603 OS can enable both readings. The 0411 can show oil pressure through serial data using a Corvette segment, but more testing is needed to find the voltage through serial data. It seems possible since the battery light comes through the data line.

How to Enable Oil Pressure and Voltage through the class 2 data line on a P59
To enable the last gauges, you'll need to complete a few steps. Switching to a p59 setup takes some effort, but it's beneficial. After that, the process becomes much easier.

Oil pressure data will be sent through the dataline once you provide a p59 with an oil pressure reading. To do this, replace the old 1-wire oil pressure switch with a 3-wire sensor designed for 03+ trucks. Investing in a specialty socket makes this easier. I found the sensor and pigtail for about $15, and they have the same threads. Connect all three wires to the p59 to ensure the oil pressure gauge functions properly.

Voltage over class 2 is even easier as all you need to do is modify the bin file for your pcm and flash it. in the 7603 OS you will need to open a hex editor, set the byte width to 18. Then you will find 5 bits in a vertical row that are all 38.

Replace all 5 instances of 38 with 3A. Ensure you are changing the byte, as the file size cannot be altered on that flash.

When switching to a p59, note that the 7603 OS is from 2004. This model changed the fuel system, causing the fuel gauge to read backward compared to earlier models. The easy solution is to adjust a setting in the universal patcher.

Open a compare bin from a 2003 truck with the same fuel tank size and copy that table to fix the fuel gauge.