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jamesjones
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Jul 23, 2015, 2:14 PM
Post #1 of 23
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dash goes haywire
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My 1996 chevy silverado 4x4 5.7 ltr. is running weird sometimes. the problem is that while driving the dash goes haywire. the tach drops to zero, the speedometer advances to 100mph and the transmission down shifts to 2nd. this is a intermittent problem. i changed battery and lugs and instrument cluster still no change. there are no check engine lights and no codes. had it scanned at local shop and everything is clear. dont know what to do any help will be greatly appreciated thank you
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Tom Greenleaf
Ultimate Carjunky
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Jul 24, 2015, 2:36 AM
Post #2 of 23
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Re: dash goes haywire
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Mostly IDK but would think this is a plug connection to the cluster likely right up over pedals. Hard to see anything up there if this has A/C, PDLocks, a remote for them and an air bag. The 2500 was exempt from the air bag TMK for most.
Did codes read and say nothing or not read? Does CEL light come on at all?
For right now it's behaving that it has defaulted to limp mode for driving and would keep that to a minimum and fix this now.
#1 question is does it have any aftermarket alarms, remote start or recent work on anything under dash?
T
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jamesjones
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Jul 24, 2015, 3:57 PM
Post #3 of 23
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Re: dash goes haywire
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scanner not reading any codes and CEL is coming on when this happens. dont know if any work was done on the truck recently. I actually just got this truck . i put new cluster in because i was told that the cluster may be the problem. I will check all connections under dash. do I need to take cluster out to do this or are they accessible from the under side of dash
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jamesjones
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Jul 24, 2015, 4:01 PM
Post #4 of 23
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Re: dash goes haywire
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No after market parts or alarms. It is a K 1500 series truck.
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Tom Greenleaf
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Jul 24, 2015, 4:11 PM
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Re: dash goes haywire
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Now I don't know what to say. It won't read codes is problem one now and why. I'm not sure you can just swap whole clusters and have them work without dealer help.
Now there's question as to what wiring has been messed up such that it's anyone's guess and probably have to sit there with a wiring diagram looking for each one to be in the right place still and working as it should. Could be real troublesome to fix this,
T
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jamesjones
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Jul 24, 2015, 4:43 PM
Post #6 of 23
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Re: dash goes haywire
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I just scanned the truck again and the codes it gave were P1864 and PO748. after scanning I fired the truck up and ll went back to working. NO check engine light on , gear selector light back on and truck running fine. Even when all this happens the engine runs fine. This one really has me and a few others stumped....
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Discretesignals
Ultimate Carjunky
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Jul 24, 2015, 5:16 PM
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Re: dash goes haywire
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I'd be suspecting a failing ignition switch. To confirm use a volt meter and measure the voltage at the trans (fuse 20) and gages (fuse 4) fuses in the IP fuse panel when the problem is occurring. They should both be battery voltage. If your missing voltage or the voltage is really low, measure the voltage at the ignition switch itself on the white and two red wires. They should all be battery voltage. If both reds are good and the white isn't, replace the ignition switch. If you have battery voltage at the fuses when the problem is occurring, let us know.
Note: Don't disconnect anything or remove the fuses when your making your measurements. You're doing a voltage drop test, so make sure your meter is grounded to the battery negative. You may need a jumper lead to be able to reach.
Also measure on both sides of the fuses. Take some measurements when the problem isn't occurring, so you know where to take measurements and can see what it is supposed to be. That way you can tell the difference between what is normal and what isn't.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Jul 24, 2015, 5:23 PM)
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jamesjones
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Jul 25, 2015, 4:50 AM
Post #8 of 23
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Re: dash goes haywire
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does the truck need to be running while testing this or just ignition in the on position .
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jamesjones
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Jul 25, 2015, 7:37 AM
Post #9 of 23
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Re: dash goes haywire
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This is the out come of the test... fuse 4 when problem is occuring : top side of fuse 14.09 volts Bottom of fuse 14.09 volts . Fuse 20 when problem is occuring: top of fuse O volts. bottom of fuse O volts.. Fuse 4 When problem not occuring : 13.80-14.04 on both sides of fuse. Fuse 20 when problem not occuring: O volts on top and bottom..
Ignition wires : RED 14.26 while good
Red/ white stripe 14.12 while good
Did not find a White wire ? and still need to test ignition when bad
Here is a list of wires in ignition ... large wires RED. RED/WHITE STRIPE. YELLOW . PINK. PINK/WHITE STRIPE. ORANGE. BLACK(or brown really hard to destinguise).. medium wire . BLACK. small wires .. GREEN. BLACK. BROWN. TAN/WHITE..
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Discretesignals
Ultimate Carjunky
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Jul 25, 2015, 7:52 AM
Post #10 of 23
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Re: dash goes haywire
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I want to appologize. The white wire is actually pink/white on the early models. They went to white in the later models. The pink/white is the feed for fuse 20 and the pink wire is the feed for fuse 4.
Fuse 20 protects the circuits for the solenoids inside the transmission and also powers part of the instrument cluster. If the power is lost to the transmission, it will default to 3rd if it is a 4L60E and 2nd gear if it is a 4L80E. Of course if you lose power at that fuse, the cluster takes a dive also.
Kind of strange you show no voltage on fuse 20 when the problem is not occurring because if that were the case the transmission would be default and your cluster would be dead.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Jul 25, 2015, 8:11 AM)
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jamesjones
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Jul 25, 2015, 8:20 AM
Post #11 of 23
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Re: dash goes haywire
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rechecked everything and this is what i have found
RED 14.18
RED/WHITE 14.08
PINK 14.02
PINK /WHITE O.92
ORANGE 14.14
BROWN (black) 14.13
Yellow O
was able to test in both senerios and same outcome . The tach when running good is reading aruond 1200rpm but scanner only shows 850rpm . Is there any way i could possible talk to you on the phone??? IF so my number is (deleted). I want to make sure that I am not doing something wrong. I cant tell you how much i appreciate your time and knowledge on this
(This post was edited by Discretesignals on Jul 25, 2015, 8:26 AM)
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Discretesignals
Ultimate Carjunky
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Jul 25, 2015, 8:25 AM
Post #12 of 23
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Re: dash goes haywire
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RED 14.18
RED/WHITE 14.08
PINK 14.02
PINK /WHITE O.92
ORANGE 14.14
BROWN (black) 14.13
Won't need to call you because it needs an ignition switch. You did good with your measurements.  I deleted your number, so you don't get freaks calling you.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Jul 25, 2015, 8:29 AM)
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jamesjones
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Jul 25, 2015, 8:30 AM
Post #13 of 23
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Re: dash goes haywire
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I also put new starter and battery in and the starter sometimes does not fully ingage. you have to toggle the ignition on and off to get it to ingage ..
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Discretesignals
Ultimate Carjunky
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Jul 25, 2015, 8:33 AM
Post #14 of 23
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Re: dash goes haywire
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It could be related to your starter issue. The fact you have voltage on the red wire and no voltage on pink/white and voltage on pink tells me that you have the ignition on and the part of the switch that makes contact between pink/white and red has failed.
The switch has five contacts inside it, so really it should be called ignition switches...
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Jul 25, 2015, 8:34 AM)
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jamesjones
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Jul 25, 2015, 8:33 AM
Post #15 of 23
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Re: dash goes haywire
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when you say Ignition are you saying key cylinder or ignition wiring harness or both.. thank you again this means alot....
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Discretesignals
Ultimate Carjunky
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Jul 25, 2015, 8:38 AM
Post #16 of 23
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Re: dash goes haywire
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This part:
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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jamesjones
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Jul 27, 2015, 7:31 AM
Post #17 of 23
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Re: dash goes haywire
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changed the ignition starter switch and ignition lock cylinder. I have power to all wires now but still nothing to fuse 20 . No engine codes but to other codes P1886 shift timing solenoid and P1864 torque convertor clutch circuit .... starter still acting up and rpm still not reading right
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Discretesignals
Ultimate Carjunky
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Jul 27, 2015, 4:58 PM
Post #18 of 23
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Re: dash goes haywire
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Darn, I thought we had this one based on the test results you got.  Back to the drawing board.
Fuse 20 is for the transmission solenoids, so that might be why your getting solenoid circuit codes. You stated you have power on your pink/white wire at the switch, but no power on fuse 20? If that is the case, there has to be something going on between the ignition switch and the fuse block. You might have to go in there and do a visual of the wiring and maybe the fuse panel itself. If you had a power probe you could power the circuit up at fuse 20 to be sure everything comes back on. You could also use a fused jumper to power up the circuit too.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Jul 27, 2015, 5:02 PM)
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jamesjones
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Jul 30, 2015, 4:48 PM
Post #19 of 23
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Re: dash goes haywire
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I think all problems are solved with exception of tach and speedometer.. I checked fuse 20 with ignition on and its got 13 volts I looked at some wiring schematics and its saying that fuse 20 is dead unless the ignition is in on or run position.. all gauges on dash seem to be reading correct except for tach and MPH is there still something im overlooking or does this cluster need to be calibrated?? I also ran the jumper wire from the MAXI fuse on firewall under hood straight to the back of fuse 20 on inside panel and it was back feeding and the PRNDL light stayed on with ignition off ...are the clusters in these trucks year specific the reason i ask is the cluster i put in was out of a 1997 K1500 4x4 ?????
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Discretesignals
Ultimate Carjunky
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Jul 31, 2015, 4:06 AM
Post #20 of 23
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Re: dash goes haywire
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I'm confused. In one post you state you have no power on fuse 20 and then the next post you state you have 13 volts. So, your other problems with transmission going into default and the tranny codes are solved?
Your right, fuse 20 is only hot in run and start.
Do you still have the old cluster? If so, if you reinstall it, does it act the same way?
I believe the clusters from 96 to 97 are interchangeable.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Jul 31, 2015, 4:10 AM)
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jamesjones
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Aug 4, 2015, 3:59 PM
Post #21 of 23
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Re: dash goes haywire
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Sorry it took so long to get back ... I was giving the truck time to see if it was going to act up again and so far all is good.. I did have the old cluster and i put it back in and seems to be better. I think some of it has to do with the oversized tires on the truck. I think its about 10 mph off. the gas gauge acts funny . when you apply brakes it moves around alot but i think i can deal with that... I had a few people tell me different things and the information I got from you was 100% correct and again thanks so much Discretesignals . The transmission is shifting smooth and going through all gears ..... I reset all codes and nothing else has popped up after 4 days !!!!
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Discretesignals
Ultimate Carjunky
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Aug 4, 2015, 4:55 PM
Post #22 of 23
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Re: dash goes haywire
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That's good to read.
If the tire size isn't too extreme, you can actually get the PCM programmed to correct the speedometer error.
I'll keep your thread open for awhile if anything pops up.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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Tom Greenleaf
Ultimate Carjunky
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Aug 5, 2015, 2:55 AM
Post #23 of 23
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Re: dash goes haywire
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Just note on gas gauge: Own similar. Gauge does move if lower 1/3 of fuel not on top 1/3 both braking and accelerating. Long tank on frame - think it's totally normal, T
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