Help! All Gauges Not Working!
 

Installed new alternator and now truck runs and charges fine. It's just I have no gauges now! All gauges read zero? Voltage, tach, fuel, oil, temp everything!!! Help! :humm:

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Let me give more detail.

Everything works with the dash except the gauges.... they set themselves to the base level during ignition but do not move after that.

Is this a PCM or instrument cluster issue?

I did the steps found here for standard diagnosis (everything passed except Wait to Start didnt come on)

DodgeForum.com - View Single Post - Will not start, Gauges do not read, Airbag Light

I had the same issue on my 95, the cause was a bad crankshaft positioning sensor but it also prevented the overdrive from working and alternator from charging. Im sure someone with more insight will be able to chime in but if not the cps might be worth looking at. Sorry i cant help more. good luck.

So your fuel gauge didn't work because of the CPS???
Usually the fuel and voltage gauges work whether the truck is running or not.....

This confuses me.

The alternator is charging though and the overdrive works fine.....

I appreciate any assistance though so thanks for your time

check the grounds of the cluster

taking a guess I am thinking a bus comunication issue
central timer could be a issue too, ive seen these go bad and take down the entire bus

get a scan tool and check for codes , good chance you have a loss of comincation with the cluster

if you wanna get real deep idle voltage to ground should be about 2.5ish volts on either buss wire at idle.. buss idle not engine idle no disrespect intended just trying to be clear bus - is wt/bk bus+ is vt/bk if KOEO there is less or more than 2.5v on either buss line to ground there is a issue

Thanks for the info trucksmoke.

I took the truck to the dealer. The mechanic started the truck.... all the gauges were at zero as usual... he plugged in the scanner... didnt see an error.... he tapped on a few places around the dash above the instrument cluster with his hand and bam! All gauges jumped up to their correct positions. All the gauges have worked fine since. So the conclusion is.. the instrument cluster is probably goin bad.... but its working for now.

Not to be a jerk but theres no way bus can be checked in this manner. You could use a scope to watch "data packets" but hooking a volt meter up wont tell you anything its just a average voltage reading which will increase or decrease with communication across the bus. There is no spec for bus voltage and while I've seen known good wave forms for the bus circuit not one of these trucks will produce the same wave form twice in the communication circuit indicating that the average voltage method couldn't be used to determine pass/fail of communications, even with communications at idle any activation of any system communication will cause voltage changes. This method could give some insight but it would be constant 0v or 12v for a failed circuit and more than likely used by a pro tech as opposed to a DIyourselfer lol.
On the other hand glad the o/p got his truck fixed.

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you are right, you cannot decipher bianary logic on a bus with a dmm, im pretty sure you cant even get it unless you have a very badass occiliscope
that wasn't my intent, I do check can-c IHS and STAR busses all the time with a dmm, most of the time I am checking resistance values since I already there is a break in a wire
bus idle.. basically when nothing is going on, engine not running and initial meet and greet for all the modules has been completed ... takes about 2-3 seconds after KO
this idle voltage will be about 2.5v since no communication is being broadcasted and this is a 5v can-c bus a dmm will show roughly 2.3-2.7v
It was a down and dirty test and if he did find a issue here it would have helped me find a better diagnosis, beating on the dash works too :jump:

I didn't mean to make too big of a leap with my suggestions , I do realize most are DYIers but the more info I have the easier it is for me to help you
on the other hand you can come pay my dealership 89 bucks and ill do all the diag work for you:c:

I see your logic, I'm not saying your logic is wrong. I'm just saying that we can't determine the health of a bus circuit just by looking at voltage on the circuit, we can theoretically see if its completely down I guess but we don't gain any further knowledge. We could say that if voltage was low and came up when say a bcm is unplugged that its possibly a issue with that module.
All of which typically set a u or b code.
For poops and giggles I look at communication circuits with the modis when i have the time and usually can get a clear picture and can determine some type of communication either is or is not happening but short of extensive protocol research and a engineering degree i doubt anyone could decipher what it was doing.
Again I'm not trying to question you're diagnostic procedure, i just wanted to mention we can't really give bus communications a pass or fail with just that information. And thats just my opinion, I'm always interested in learning something new. I urge you to try an dso when working with communications. I've found that I have a better grasp on the data in graph form.
Im not much for the bang on the dash theory myself, they usually shatter if I do lol
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