99 f550 Speedometer not working
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99 f550 Speedometer not working
So I have an issue with my speedometer and I've checked or replaced all usual suspects abs sensor in the diff fuses so what it's doing is when you start the truck in the morning the abs light is on and the speedometer doesn't work until the truck gets good and warmed up and the heat has been on then the abs light kinda flickers off and the the speedometer will work fine I tried using a snap on scanner on it and it say abs system unavailable if I try to see what's going on anyone have this kind of issue or know of a fix
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From: Virginia
Here is some info.
Vehicle Speed Sensor (VSS)
The VSS has been deleted for 1999. On vehicles equipped with 4-wheel anti-lock brake systems (4WABS), the vehicle speed signal is generated by the rear anti-lock brake sensor and sent to the 4WABS module. The 4WABS module sends the vehicle speed signal via circuit 679 (GY/BK) to all systems that require a vehicle speed signal input. Vehicles equipped with rear anti-lock brakes (RABS) generate a vehicle speed signal from the rear axle speed sensor. The generic electronic module (GEM) receives this signal (VSS_GEM) for internal use and then distributes it to the appropriate other users (i.e., the powertrain control module [PCM], speed control module, and speedometer).
Speedometer
The electronic speedometer (17255) receives a speed signal from the 4WABS module (if equipped with 4WABS) or the GEM/CTM (if equipped with RABS).
Odometer
A million-mile tamper-resistant odometer is standard. Replacement speedometers have a resettable odometer.
Do you have RABS or 4 wheel ABS? If you have RABS, the above indicates that the VSS signal goes into the GEM. I will tell you the smaller trucks had a terrible problem these years with windshield leaks. They would have a minor leak that would run down the firewall and get into the GEM and cause corrosion and all kinds of havoc. You may want to pull the GEM and look for signs of corrosion. It would also get into the fuse box and cause problems there too.
If you have 4 wheel ABS, they say the vss signal goes into a 4WABS module located somewhere. If that is in the interior, you might want to pull it, look at it, and then put it back. Sometimes just messing with something will make it start working again.
Vehicle Speed Sensor (VSS)
The VSS has been deleted for 1999. On vehicles equipped with 4-wheel anti-lock brake systems (4WABS), the vehicle speed signal is generated by the rear anti-lock brake sensor and sent to the 4WABS module. The 4WABS module sends the vehicle speed signal via circuit 679 (GY/BK) to all systems that require a vehicle speed signal input. Vehicles equipped with rear anti-lock brakes (RABS) generate a vehicle speed signal from the rear axle speed sensor. The generic electronic module (GEM) receives this signal (VSS_GEM) for internal use and then distributes it to the appropriate other users (i.e., the powertrain control module [PCM], speed control module, and speedometer).
Speedometer
The electronic speedometer (17255) receives a speed signal from the 4WABS module (if equipped with 4WABS) or the GEM/CTM (if equipped with RABS).
Odometer
A million-mile tamper-resistant odometer is standard. Replacement speedometers have a resettable odometer.
Do you have RABS or 4 wheel ABS? If you have RABS, the above indicates that the VSS signal goes into the GEM. I will tell you the smaller trucks had a terrible problem these years with windshield leaks. They would have a minor leak that would run down the firewall and get into the GEM and cause corrosion and all kinds of havoc. You may want to pull the GEM and look for signs of corrosion. It would also get into the fuse box and cause problems there too.
If you have 4 wheel ABS, they say the vss signal goes into a 4WABS module located somewhere. If that is in the interior, you might want to pull it, look at it, and then put it back. Sometimes just messing with something will make it start working again.
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tperk100
1999 - 2016 Super Duty
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Oct 28, 2017 02:42 AM
