Obd2 rpm discrepancy
- Thread starter slowstart
- Start date
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I have been using the 1998 manual as a guid because there are lots of similarities but when something is different i dont know if it is actualy difrent (and should be like it is in the manual) or if it is correct and they made changes for that year.
There are more manuals available for download in that thread after the original post. 1999 manuals were added by @xXxPARAGONxXx on page 12, those should be closer to what you need. I'd imagine the changes between 1999 and 2000 were very minimal.
https://www.gmt400.com/threads/88-98-service-manuals.43575/page-12
Assuming you have a 4L80E, it sound like your forward drum has deep grooves cut into it's inner diameter where the input shaft sealing rings are located. One of the most common problems on those units. These grooves allow apply fluid to blow by/bleed out instead of going to the apply piston. The apply piston can't fully compress your clutch pack until you basically floor it to get the pressure high enough to offset the bleed/leak in the circuit.
Plug your scan tool back in, take for another drive and bring up live engine data - check all read outs for the TPS, MAF and other sensors. If their data streams dont indicate anything is wrong with them, bring up live transmission data. Ensure the gear your in per your pcm is the gear you're actually in while driving. Check for transmission-specifi DTCs (shift solenoid performance, input speed sensor (check the ISS by swapping it with the OSS - if no change, no SS codes, speed sensors are fine), gear error ratio error codes, psma, etc.
Lastly, drop the pan, check the filter, bottom of the pan and filter pick up seal...
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Greetings slowstart,
Nice to cross paths with you in the GMT400 forum. There's a lot of helpful
folks here that share your good taste in trucks and the desire to keep them
on the road for a good, long while.
I have a '99 C2500 also with the 7.4, and I have been using the '99 C/K
Factory Service Manuals found in reply #77 of the service manual thread.
The reason I share this is that these manuals should also work no
problem for your 2000, for as far as I know no major changes were made
from when my truck was made to yours: ('99 C/K Manuals, Vol 1-4)
Best of luck --
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Thank you all so much for your replies. I will do a bit more investigating this weekend and try out the advice and suggestions here along with the resources pointed out. I will report back with more information. Thank you all so much! This forum is amazing!!
Oh p.s. my live data takes forever to update on my reader. Is that common with these trucks or is there a compatability issure or something else going on with my reader (innova 5610)? When I plug it into my wifes van (honda odyssey) the live data is instantly updated giving real time results but with this truck it only seems to update every 30 seconds or so. Is that normal?
Oh p.s. my live data takes forever to update on my reader. Is that common with these trucks or is there a compatability issure or something else going on with my reader (innova 5610)? When I plug it into my wifes van (honda odyssey) the live data is instantly updated giving real time results but with this truck it only seems to update every 30 seconds or so. Is that normal?
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While I wait to find time to investigate the transmission issues further. I am still curious what is going on with my obd2 reader. I have never had one before, so I am not familiar with what is normal behavior or not. I know some of the live data is wrong (rpm for example), so I worry what else might be wrong. Also, is it normal for the live data to only update once every 30 seconds to a minute? After getting the obd2 tool, I tried it on my wife’s vehicle (only other vehicle we have new enough to have an obd2 port) and the live data was… live. It updated instantly and I could see everything that was happening as it happened. Is that just how these trucks are (slow) or is it a compatibility issue with my reader and the truck or is it a symptom of something going bad with the truck computer. Using google, the only thing I found was on a Toyota 4 runner forum, but the problem was specific to his reader truck set up so nut much help for me.
TLDR: is it normal for the live obd2 data to be really slow on these trucks?
TLDR: is it normal for the live obd2 data to be really slow on these trucks?
No, it should be displaying live, real time data...If the scanner is functioning normally on your wife's vehicle, perhaps there's something in/with your truck impeding comms to the scan tool. I have two 2000s era Chevy trucks and both render live data as expected using my TECH2 and SnapOn scanners.
I may depend the scan tool or how it’s being used.
One tool I have, "AutoTap" interfaces to my laptop and will allow me to monitor all / any parameters on my 1998, for example in a large, spreadsheet like display. The problem is that, when monitoring a large number of parameters, the refresh time is long. IIRC, with AutoTap at least, the ECU can send about 40 parameter updates per second (I'm going from memory here... 40, or 20...), e.g., if I’m monitoring 40 different parameters in the “spreadsheet” display, I only see each parameter update once per second. That’s too slow for my liking. Generally, the parameters' refresh time in seconds equals the "number of parameters monitored" divided by 40… at least in this example. So when monitoring a large number of parameters the updates come slowly, and vice versa.
If I want to monitor in real time, I’ll configure AutoTap to monitor only one or two parameters, thus allowing each parameter to be updated more often.
The root of the matter seems to lie with the ECU's ability to send information and/or the AutoTap scan tool's ability to extract information from the ECU.
I’ve not used EFILive as a monitoring tool, so others will have to comment on how fast it (or others) will update a set of parameters.
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