Changed Speed Sensor, now what?
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Changed Speed Sensor, now what?
Hey I have a 1996 Ford F250 7.3, Having trouble with not wanting to shift into second gear. Tranny is a E40D. I can shift it into second manually. I have no codes showing up? Was told to change the speed sensor on the read differential. Did that and now at 40 MPH the speedometer and tact start to jump around? And to boot the truck is still not shifting into second?
Please help....
mnc87
Please help....
mnc87
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Reply....
question what does the 3rd brake light have to do with this?
mnc87
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Cargo Master
Joined: Jul 2006
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From: Nampa, ID
IIRC, the third brake light and the VSS system are interconnected. If the third brake light is out, the VSS system can provide inaccurate signals and cause issues. I'm attempting to verify my line of thinking on this, but haven't found the info yet. Someone will either confirm or refute my thought process soon.
Lead Driver
Joined: Oct 2003
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From: Madison, WI
Center stop light and VSS are not connected. Two different issues, both which can cause problems with the E4OD:
* Burned out center stop light will, when you hit a turn signal, send a sneak circuit current to the brake light switch circuit. This makes the PCM think you've hit the brake pedal, and will unlock the torque converter (and interrupt the cruise)
* VSS provides the speed signal to both the speedometer and the PCM for E4OD shift programming. Bad VSS, or wiring/connector (or tone ring, diff fluid contamination, etc) will cause the speedometer to fluctuate, and will send a simillar fluctuating speed signal to the PCM, which makes it have "fits" about when to shift the E4OD. IIRC, aftermarket VSS are hit-and-miss, so if you have better speedometer accuracy with the old VSS, I would recommission it.
So both need to be in good working order (unless, of course, you have a ZF5...
).
* Burned out center stop light will, when you hit a turn signal, send a sneak circuit current to the brake light switch circuit. This makes the PCM think you've hit the brake pedal, and will unlock the torque converter (and interrupt the cruise)
* VSS provides the speed signal to both the speedometer and the PCM for E4OD shift programming. Bad VSS, or wiring/connector (or tone ring, diff fluid contamination, etc) will cause the speedometer to fluctuate, and will send a simillar fluctuating speed signal to the PCM, which makes it have "fits" about when to shift the E4OD. IIRC, aftermarket VSS are hit-and-miss, so if you have better speedometer accuracy with the old VSS, I would recommission it.
So both need to be in good working order (unless, of course, you have a ZF5...
).
Cargo Master
Joined: Jul 2006
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From: Nampa, ID
There you go. That's what I was trying to find. I knew the third brake light was involved somehow, but wasn't sure. I'm already subscribed to this thread, so hopefully I'll get it right next time.
Cargo Master
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3rd brake light out causes trouble with the cruise system shutting down.
Cargo Master
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As far as VSS goes, did you remove the loom and inspect the wiring? I found a nick in mine when I had similar trouble and then corrosion was wicking up the wire. I cut the wire as far back as I could to stop it and cleaned the wire and crimped it back together.
New User
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Speaking of differential VSS. I had intermittant "engine light, speedo, heat gauge & tack" would stop working for about 100 KM/fuel tank. I replaced the diff VSS and now I get frequent intermittant tack & speedo failure and occasional as before. Are there more sensors to suspect? I'd be grateful for suggestions. the vehicle runs well...
Postmaster
Joined: Mar 2004
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Speaking of differential VSS. I had intermittant "engine light, speedo, heat gauge & tack" would stop working for about 100 KM/fuel tank. I replaced the diff VSS and now I get frequent intermittant tack & speedo failure and occasional as before. Are there more sensors to suspect? I'd be grateful for suggestions. the vehicle runs well...