Aftermarket MPG Computer?

I have the dash, here is a picture of the connector on the button pad on the RH dash panel. I'll have to look in my harness again, but I don't think I have one like that, just the ones in the previous pictures. This will suck if it won't work, I have a nice cluster out of a Century. Changing the whole harness would be a major pain and expensive, I bet there has to be a way to splice into it if it doesn't have the right one.

 

Well, I spent several hours in my local dealer the other day, got the main dash wiring harness layouts from both the century dash (ICU2) and my truck (ICU3). There is a difference, quite a few pages worth, and I see the connector for this last pic in the icu2 schematics but not in mine. Now either they're completely different harnesses, and mine doesn't have the connector, or it was just left out of the drawing because it's not used. I'm gonna go digging in my harness tomorrow and look again.

According to FL, and the parts manager here called TS on the phone for them. There is a difference in the harness for CAT and Detroit (mine is cat) and after '04. Those I can understand, but like you, I find it difficult to believe they made two separate ones for the two cab models.

The icu2 layout I have shows the 8 pin connector and lists the circuits they go to. (ie, 437B, 437C) Also noticed those are listed in the main LH cluster plugs, but those pins are shown not used in mine. I did a side by side comparison of the pinouts for both and only a few differences, like the pins for outside temp on the icu2, abs trailer (prob an idiot light), and mainly 6 of those 437 circuits.

Now I thought I remember mine having wiring to all or most pins, I'll look tomorrow, so either they're in the harness and not broken out to the extra connector or just not used wires. It might be that these wires only connect the keypad to the main dash cluster and have absolutely nothing to do with the ecu. They're listed as "ICU KEY PAD/TRIP INFO SW" and "ICU KEY PAD SIG" with numbers.

 

Well, apparently mine does not have the provisions for that in the wiring harness after all. Those pins have no wires, but I'm pretty sure now all you have to do is install wires to those correct pins from the button pad. I can even splice my ext temp sender wires into the back of the dash for outside temp.

I plugged it up and started the truck, all gauges worked except the boost, pyro, and two rear diff temps. So I guess I'll be adding some sensors. Hopefully, the wiring harness has the sensor connectors.

 

I think so, if you don't mind doing a little wiring. It may be that your model could have the connector. (the 8pin above) If so, you're set. If not, you'll probably have to do what I'm doing, I ordered the connectors from FL, have to wait a week then I'll know if it works or not.

If you look at the schematics, the connections from the keypad go directly into the main cluster. Those wires are just not there one my harness. All they do is control the display. There are only two connections from the cluster to the ECU, a single serial connection. The rest are for lights and temp etc, and the buttons.

Now adding the extra gauge sensors could prove more fun. If my engine harness doesn't have the connections for the boost and pyro, I'll have to figure out how to wire them in or replace the harness. I need to find a VIN from a truck with a CAT and full gauges to compare.

 

I was wrong about the boost, it works, had to hookup the cluster and go down the block to verify. I think all of the electronic engines now have the sensor. I'll try to get some pics of the install later, I should let you know by next week if it works for sure.

So far I did pop in the main LH cluster, no control over the display yet but the gauges work good, minus the pyro and diffs. Even the MPG bar on the top that goes from - to + to show you load works. The only display I can see that comes up while driving now is I guess avg mpg and a mile reading that started at 0.0 mi, I figured the odo reading would show, but I can only wait until I get the pad hooked up.