Hey guys...

Ran into an odd problem on my Tahoe... Finally got around to getting my tach and speedo working... speedo works great... tach does too... however when the CPS is hooked up, I sometimes lose my fuel level, oil pressure, and coolant temp gauges... they drop to zero.

With the CPS hooked up, when I click the key to run, all the gauges come up fine... when I start the truck, I sometimes lose oil pressure, temp, and fuel level gagues...

Unhook the CPS and all the gauges work fine besides the tach.

I'm running out of ideas... cant find anyone that's had similar issues.. I'm leaning towards a ground issue but where?

Anyways... if anyone has any ideas... chime in please.

-Chris

 

It's interrupting serial data communication on the data bus. All of that information is serial data from the pcm to the instrument cluster.

 

I just noticed that with the cps hooked up, its kicking on the anti-theft light.

Would that kill the gauges or what have you?

With it unhooked, the anti-theft light stays off and the other gauges work fine.

-Chris

 

Just side note... with the key in the on position... the theft light comes on then goes back off like normal... it only comes on and stays on with the engine running which is also when the gauges stop working.

Ideas on what would cause this?

 

The CPS is killing communication on the databus causing non functional gauges and anti-theft lamp to illuminate it's all databus information.

Whatever the cps thing you are talking about is what's causing all of your problems.

 

the CPS is the crank position sensor.

Next question is... is it the sensor itself or a wiring issue related to it? Why are only 3 gauges failing and not the whole cluster? The speedometer, tach, and voltmeter still function when the crank position sensor is plugged in.. as well as the odometer...

However the warnings I ushually get (check oil level, reduced engine power, etc.) stop coming up as well when the cps is plugged in...

The sensor itself came out of the 5.3 that was in the truck and it wasn't having issues before when the original motor was still in... that's why I'm curious if its the sensor itself or something related to it.

-Chris

 

maybe becasue its not seeing a cam pos sensor reading?

 

I wouldn't think so... I would have thought it would cause an issue with the tach or something... but the tach works perfectly... the cluster just freaks out a little...

It also won't let me cycle through the items such as trip mileage, hrs, fuel mileage... just stays on the odometer which works fine.

So what could cause the interruption of the serial bus?

 

How exactly is the factory LS PCM interfaced into the cummins. Describe how it is setup. Did you install the OE LS sensors into the cummins and modify the OE harness accordingly.