Hey guys,

I've spent the better part of several days using the search function trying to find a solution to my problem, but I've come to the end of my rope, and am resorting to posting a thread.

When I obtained my Blazer (the info of which is in my sig), the dashboard was going absolutely bonkers. The tach would slam back and forth between 0-6k rpm, all of the warning lights would come on, sometimes they would flicker, the odometer would be nothing but gibberish, etc etc etc. Well, when I got it home, I unhooked the negative battery cable because I didn't want it to BBQ in my driveway, and left it that way for a couple of hours while I signed up here, searched around, etc. Well, I hooked it all back up, and my dashboard is completely fine now, except for three things.

The gear diplay does not work, the odometer reads in kilometers, and the speedometer reads 10mph too slow. Now, these are not major issues, just things that I am kind of miffed with, and wonder if they're possible to fix. As per my searching, I've cleaned up the grounds under the hood, and made sure all cables and wires were nice and tight. Problem is my dash issues still persist. I know the speedo could be tire size (it's got old Wild Country 215/75/15's on now), and the lack of a gear display doesn't really bug me.

I'm just curious about this one fact...does anyone know why my odometer reads in kilometers? And is there any known fix for that issue? I could figure out how many miles I have, except the gauge only read 500km when I got it, and it's not at 1300km. I dunno if the cluster has been changed or what.

Thanks in advance for any insight,
Aaron

 

Can't offer any help with your cluster, but I would say it sounds like your ECM is screwed up. That's where the data is stored for electronic clusters.

Odometer in KMs with speedo in MPH leads me to believe it's the ECM.
The difference is .375 , so 100kph = 62mph. Are you sure about MPH being 10mph off, or is it really registering in the metric area? (Canadian computer swap-out maybe?)

The Tach jumping sure does sound like a bad connection somewhere.
Check the 4 plugs on the ECM.

 

Well, I see to have fixed the tach jumping around simply by unhooking the negative battery terminal and hooking it back up. As for the Speedo, I'm pretty sure it's about 10mph slow. When it reads 55mph, I'm pretty much keeping up with traffic. When it reads 60, I'm passing a few people here and there. At 65, I feel like I'm absolutely flying and passing people left and right.

I'll check all the connections. Is the ECM the box under the hood with the heatsink on top that reads "black" and "white"? That might actually be the PCM....

 

Well, that's a pretty subjective way to gauge your speed. When you're doing 60mph what rpm is the tach reading?
I agree with the idea that the PCM is not correctly programmed. It may have to be reflashed by a GM dealer. How long have you had the truck and where did it come from?

 

~2200 RPM at 60mph on my speedo. I have no idea how accurate that tach is either. It's not like GM is known for quality control when it comes to instrument clusters. I timed myself between mile markers today. With my cruise set at 50mph, I went one mile in right at 60.xx seconds. My speedometer is indeed 10mph slow.

I've had the truck about 5 days, and I traded it to some guy for my 1996 Grand Prix. I have no idea where it came from prior to that. He said that he bought it for his son, and his son refused to drive it.

 

Yep, the RPMs and the marker time all add up. I would take it to the Chevy dealer for a PCM reflash. Should run ~$80.
Well, I hope the ungrateful little jerk is still walking to a job to afford his own car.

 

I genuinely appreciate your help. I'm not that worried about it. I was more curious than anything. Also wanted to post it up if anyone else had the same problem. My main focus ATM is a windshield and slop in the steering. I just wondered if this was something I could fix on my own like the wiper pulse board or the third brake light LOL!

 

i was just wondering if you figured it out yet?

 

The OP hasn't signed on since 7-6-2011.

*Thread Closed*