Speedometer Wander & Cruise Surge
#1
02-15-2004, 02:19 PM
Join Date: Feb 2004
Location: Alberta, Canada
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Speedometer Wander & Cruise Surge
Hi, I'm new and would appreciate any help on this. My truck is a 1998 F150 4X4 Extcab 4.6L with 150K kms.
The speedometer on my truck wanders by about 3-5 kilometers per hour. Not a big problem except the cruise control surges correspondingly. The speedometer will wander on its own but will also noticably increase when I rev the engine a bit while driving and reduce when I back off on the accelerator (while the vehicle hasnt yet changed speeds significantly). This seemingly makes the cruise control surge in a somewhat rythmic pattern.
As background, the speedometer quit last week when it was very cold out and so I replaced the vehicle speed sensor (VSS) and 20 tooth gear on it (the old gear was all chewed up and mssing teeth). This got the speedometer working again and the check engine light has gone out. Note: the cruise control always did jump erradically since I bought the truck used 2 years ago so I never used it, and the speedomter may have always been wandering somewhat too, not sure.
My understanding is that for a 1998 the VSS feeds both the PCM and the GEM, and then the GEM feeds the PSOM (programable speedometer), but I dont know where the cruise control gets its vehicle speed signal from so I'm not sure where to zero in. Thinking that maybe battery voltage increasing when reving may be to blame I've checked the voltages at the battery and fuses and they are all solid at 14.5 volts irregardless of idle or reving.
Other current problems include trans OD light comes on after driving a while, but I dont know if it is related. It always did that even after changing the trans fluid.
Any suggestions on what is wrong and how to fix it would be appreciated? Thanks.
The speedometer on my truck wanders by about 3-5 kilometers per hour. Not a big problem except the cruise control surges correspondingly. The speedometer will wander on its own but will also noticably increase when I rev the engine a bit while driving and reduce when I back off on the accelerator (while the vehicle hasnt yet changed speeds significantly). This seemingly makes the cruise control surge in a somewhat rythmic pattern.
As background, the speedometer quit last week when it was very cold out and so I replaced the vehicle speed sensor (VSS) and 20 tooth gear on it (the old gear was all chewed up and mssing teeth). This got the speedometer working again and the check engine light has gone out. Note: the cruise control always did jump erradically since I bought the truck used 2 years ago so I never used it, and the speedomter may have always been wandering somewhat too, not sure.
My understanding is that for a 1998 the VSS feeds both the PCM and the GEM, and then the GEM feeds the PSOM (programable speedometer), but I dont know where the cruise control gets its vehicle speed signal from so I'm not sure where to zero in. Thinking that maybe battery voltage increasing when reving may be to blame I've checked the voltages at the battery and fuses and they are all solid at 14.5 volts irregardless of idle or reving.
Other current problems include trans OD light comes on after driving a while, but I dont know if it is related. It always did that even after changing the trans fluid.
Any suggestions on what is wrong and how to fix it would be appreciated? Thanks.
#3
02-16-2004, 07:02 PM
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