What all does the PSOM do?
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More Turbo
Joined: May 2008
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From: Beaufort, SC
What all does the PSOM do?
My 93 has been throwing a code 29 (VSS) and I can't figure out why. I replaced the RABS sensor/DSS/VSS or whatever it's called, but still get the code. I traced the wiring to it under the truck and found nothing wrong.
I read somewhere, that the VSS signal has to pass through the PSOM before it gets to the PCM. If this is true, then could my problem be in the PSOM?
I read somewhere, that the VSS signal has to pass through the PSOM before it gets to the PCM. If this is true, then could my problem be in the PSOM?
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Thread Starter
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More Turbo
Joined: May 2008
Posts: 548
Likes: 3
From: Beaufort, SC
Pulled the cluster and plugged/unplugged the PSOM several times. When I took it for a test drive, I found the speedo needle bouncing from 60-70MPH instead of 60-65MPH like it did before.
I'm tempted to pull the diff cover and inspect the ring gear for damage. With a new sensor in the diff and no obvious damage to the wires that go to it, the ring gear would seem to be all that's left to check.
I'm tempted to pull the diff cover and inspect the ring gear for damage. With a new sensor in the diff and no obvious damage to the wires that go to it, the ring gear would seem to be all that's left to check.
Fleet Mechanic
Joined: Sep 2005
Posts: 1,509
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From: Ladner, British Columbia
Code 29
It been a while but if I remember correctly, a VSS code does not always mean the VSS needs replacing.
You may just have some slippage in your tranny and the speed that the VSS is supposed to show is different that what the tranny controller is expecting.
I always saw a VSS code when my torque converter lock did not hold, it corrected itself after I replaced the torque converter, i.e. there was nothing wrong with the VSS, or wiring etc...
Hopefully this helps a little.
Seb....
You may just have some slippage in your tranny and the speed that the VSS is supposed to show is different that what the tranny controller is expecting.
I always saw a VSS code when my torque converter lock did not hold, it corrected itself after I replaced the torque converter, i.e. there was nothing wrong with the VSS, or wiring etc...
Hopefully this helps a little.
Seb....
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Joined: Aug 2007
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code 29 has nothing to do with the transmission it i strictly a vehicle speed issue
the signal goes to the PSOM it processes the signal and relays it to the PCM
a chattering torque converter clutch causes an erratic vss signal because the differential is chattering from the torque converter chatter
the processor never derives a speed signal based on the transmission
it does use the tach signal and the gear command for to approximate the vss signal
unplug your cruise control servo if equipped and recheck it also there should be a two wire connector near the EEC IV test connector this is a direct connection to the vss sensor you can connect a hertz meter to it and check the output
but since the speedo is bouncing it probably is the PSOM going south
the signal goes to the PSOM it processes the signal and relays it to the PCM
a chattering torque converter clutch causes an erratic vss signal because the differential is chattering from the torque converter chatter
the processor never derives a speed signal based on the transmission
it does use the tach signal and the gear command for to approximate the vss signal
unplug your cruise control servo if equipped and recheck it also there should be a two wire connector near the EEC IV test connector this is a direct connection to the vss sensor you can connect a hertz meter to it and check the output
but since the speedo is bouncing it probably is the PSOM going south
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