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Rebuild about done

Just got her back together. I can tell the difference. It runs like it should. the TDCO is at .18. The desired timing is still around 8.5. When we do a tdc learn or time set it drops to 3-3.5 when they are on but when we turn them off that jump back to 8.5 range. Any thoughts?
 
Rodd said:
There is one code that won't clear. It is for the transmission speed sensor. I think it may not have been plugged back in after replacing the flexplate. Anyone know where it is located?
Click to expand...
Speed sensors are on the side of the trans. one about center of the body, the other towards the rear. I can't recall which side they are on though.
 
Rodd said:
Just got her back together. I can tell the difference. It runs like it should. the TDCO is at .18. The desired timing is still around 8.5. When we do a tdc learn or time set it drops to 3-3.5 when they are on but when we turn them off that jump back to 8.5 range. Any thoughts?
Click to expand...

your using GMTDscan? once the engine is up to full operating temp, click on "Time Set" and let it idle for a bit. the number for actual deg. should drop to 3 to 3.5. don't click the off button. let it run for a while, the PCM will turn it off once it decides what value it likes. if the numbers are jumping around it can take a few minutes. Honestly I have not seen this step take more than 10 minutes.

once you see it's no longer setting timing. click the button "TDC Learn" now the idle will change some as it tries to adjust to the new offset. it will take about the same amount of time as the first step did, but will eventually land on a number and store it.

once the learn step is complete. disconnect from the truck though the software and turn off the engine. wait at least 1 full minute, then restart, connect GMTD, check codes, and check to see what your offset is and if it kept it in memory.
 
dbrannon79 said:
your using GMTDscan? once the engine is up to full operating temp, click on "Time Set" and let it idle for a bit. the number for actual deg. should drop to 3 to 3.5. don't click the off button. let it run for a while, the PCM will turn it off once it decides what value it likes. if the numbers are jumping around it can take a few minutes. Honestly I have not seen this step take more than 10 minutes.

once you see it's no longer setting timing. click the button "TDC Learn" now the idle will change some as it tries to adjust to the new offset. it will take about the same amount of time as the first step did, but will eventually land on a number and store it.

once the learn step is complete. disconnect from the truck though the software and turn off the engine. wait at least 1 full minute, then restart, connect GMTD, check codes, and check to see what your offset is and if it kept it in memory.
Click to expand...
Yes using gmtd scan. Thanks for the info. With my autoenginuity you click learn and it does it in a few seconds. I'll just leave it on.
 
All transmissions have 2 in place. All 2wd only use those two. The front is the input and the rear is the output.
4wd:
Some, not all transfer cases will use one.

Some, not all of the use only the input in the front and the transfer case as the output. For these ones the rear transmission location is only there to plug the hole. On these I have never seen a harness to the rear transmission one.

There are some applications that the signal is required from all 3 locations.

I have no clue which is which on these - just something I stumbled across over the years.
 
Found 2 identicle tss's on the trans and a different larger diameter one on the transfer case. One of the transmission ones had wires connected and the tc as well. I thought they were the same. I need to get the tc sensor now.

Strange thing happened When trying to clear the code after changing the trans sensor. Before change it wouldn't clear. After changing it now says failed to clear. We'll see what happens after swapping the tc sensor.
 
My son replaced both speed sensors and the code still won't clear. He checked the wiring looking for bad grounds or something not connected but couldn't find anything. Since it is obd1 I was thinking the code should clear if we disco the battery. He was able to set tdco at -1.78 but the timing still won't set. Any thoughts?
 
did the tdco set and remain in the PCM after shutting down and restarting? if that sets in, your golden. as for the other code, yes if it won't clear using the scan tool, a 5 minute disconnecting of the batteries will clear all codes.

once the batteries are reconnected, check codes again and see if it pops up before moving the truck. if no, then a quick drive will determine if the sensor replacement worked. you should be able to see live data from both speed sensors as well. that will tell you if it's picking up any signal at all, if erratic and whatnot.
 
dbrannon79 said:
did the tdco set and remain in the PCM after shutting down and restarting? if that sets in, your golden. as for the other code, yes if it won't clear using the scan tool, a 5 minute disconnecting of the batteries will clear all codes.

once the batteries are reconnected, check codes again and see if it pops up before moving the truck. if no, then a quick drive will determine if the sensor replacement worked. you should be able to see live data from both speed sensors as well. that will tell you if it's picking up any signal at all, if erratic and whatnot.
Click to expand...
TDCO was different before. Not sure how it got set since the timing wouldn't set. I'll have him disco the batteries for more than 5 minutes and see what happens. Thanks.
 
iirc the time set feature in GMTD or on a tech2 is just to allow you to see where the IP is at (if it needs to be adjusted before doing the TDCO) once you have the IP in or near the 3 - 3.5 deg area, then you off to set the TDCO. the TDCO is the only setting that gets retained in the PCM and should be all you have to do to set the timing.

when you reconnect the batteries and connect to the PCM, if the TDCO number is the same as what you got in your last post without functioning the time set or learn buttons (just reading what's on the screen) your good to go, no need to do any further changes, unless of course you want it closer to spec. imo I would leave it at -1.78 and call it a day. getting it any closer to spec (-0.7~) you will be there all day and then some bumping the IP back n fourth fractions of a hair's movements and re-running the learn procedure!
 
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