Setup is a 4L65e with the Novak NP241 tailshaft adapter, using a Novak-supplied pickup that looks like this:
https://www.fwmurphy.com/uploaded/MP-8802N.pdf
The MegaShift worked and reported VSS when the harness was bench tested using a TStim.
Installed, there's no signal whatsoever from the VSS. No glaring wiring problems, and the engine/trans are grounded straight to the negative terminal of the battery.
Also, the line pressure seems to be reading about 1/100th of what it should be. The values do change. I'm baffled; it seems like a wiring issue, but the wiring all checks out.
Attached log is from a run with the rear wheels on jackstands.
No signal from VSS and Line Pressure is odd
No signal from VSS and Line Pressure is odd
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- 2015-09-05_16.35.10.msl
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Bernard Fife
- Posts: 1696
- Joined: Fri Apr 04, 2008 1:28 pm
Re: No signal from VSS and Line Pressure is odd
mcneil,
The log doesn't show any sign of a VSS signal at all. Since it worked on a stim, there is likely an issue with the wiring. If this was mine I would check the VSS signal with an oscilloscope at the AMP connector. It could be that the sensor isn't positioned correctly with respect to the teeth. You could also measure the resistance across the VSS sensor at the Ampseal connector (to ground) - it should show some resistance - i.e. not zero and not infinity - ideally it should be ~975 or ~2500 Ohms (depending on which sensor you have).
I'll have a look at the line pressure issue when I get a chance.
Lance.
The log doesn't show any sign of a VSS signal at all. Since it worked on a stim, there is likely an issue with the wiring. If this was mine I would check the VSS signal with an oscilloscope at the AMP connector. It could be that the sensor isn't positioned correctly with respect to the teeth. You could also measure the resistance across the VSS sensor at the Ampseal connector (to ground) - it should show some resistance - i.e. not zero and not infinity - ideally it should be ~975 or ~2500 Ohms (depending on which sensor you have).
I'll have a look at the line pressure issue when I get a chance.
Lance.
"Never wrestle with pigs. You both get dirty and the pig likes it." - George Bernard Shaw
Re: No signal from VSS and Line Pressure is odd
Thanks, I may have a problem with my sensor.
I made a pigtail to hook my tstim into the harness. I'm using a 4-pin connector for the pressure sensor and the VSS. VSS & sensor ground connect at pin 2 and this is where I connected the Tstim.
With the Tstim connected, vehicle speed reports fine. I can't get a good reading on the sensor because my multimeter isn't reading resistance anymore (new Fluke on order), but that may be the problem.
I made a pigtail to hook my tstim into the harness. I'm using a 4-pin connector for the pressure sensor and the VSS. VSS & sensor ground connect at pin 2 and this is where I connected the Tstim.
With the Tstim connected, vehicle speed reports fine. I can't get a good reading on the sensor because my multimeter isn't reading resistance anymore (new Fluke on order), but that may be the problem.
Re: No signal from VSS and Line Pressure is odd
This was solved, problem was the sensor not deep enough. The 5/8-18 thread in the output adapter had a burr that stopped the sensor about 1/4" out, so there was no signal. Chased the thread, put it back in, and it worked fine.
A Fluke 116 with the frequency setting does a great job of reading the VSS. I can't see how I got by without one before.
A Fluke 116 with the frequency setting does a great job of reading the VSS. I can't see how I got by without one before.