Where is the Speed Sensor Located?
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Lead Lap
Joined: May 2004
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From: Florida
Originally posted by Fred Smith
Which one? There are 2. Are you showing a code? What are the symptoms?
Which one? There are 2. Are you showing a code? What are the symptoms?
I pulled the following after searching on google. This is for another car - maybe GM, but who cares I think this may be the answer to our problems. Looks like it may be the speed sensor. See my comments after the excerpt.
Excerpt form site:
http://www.salemboysauto.com/faqs/d...?Action=Q&ID=28
" 2. As your are driving down the road, the computer is watching your throttle pressure, your engine speed, your vehicle speed in mph, what gear you are in and a/c operation. As you approach 38-42 mph, if you are on level ground, if you are feathering the throttle, if the engine is warmed up, if the car is in third gear, the computer will electronically lock up the torque converter inside the transmission which makes you have direct drive, so to speak.
On this day, the driver brings the car into a shop and complains the engine is bucking and missing . What is happening is the computer sees your throttle pressure stay at 32%, sees the engine rpms stable, but sees the reported speed at 36 then a second later the computer sees 43, then 38, then 41, then 37. The computer would be confused. How can the speed be fluctuating and the engine isn’t and the drivers throttle pressure isn’t changing either? As the speed is reported above 38 mph, the torque converter clutch (TCC) is locked and when the speed is seen below 38 mph, the computer unlocked and disengages the TCC. This rapid locking and unlocking of the TCC feels EXACTLY like an engine miss to the driver. But the computer THINKS the speed sensor is going wacky so it will set the SES light to tell the driver that it sees something wrong.
In this case, the speed sensor was replaced by 3 different shops, except the SES light kept coming on, the same speed sensor code was set and the engine bucked or missed violently when the speed approached 38 to 42 mph. Clearly, the speed sensor wasn’t the problem.
In this case, what finally fixed this car was when we pulled the speedo cable and lubed it. You see when the computer saw the speed vary, it was because the speedo cable was binding up, then releasing causing the speed sensor to report this "speed up, slow down" or 38-41-36-42-34-39 speed reading. Each time the reported speed exceeded 38 the TCC was locked, each time it dropped below 38, the TCC was unlocked causing the bucking or missing. You see, the computer can only guess on the repair, it really can not tell the tech if the speed sensor is bad or the wiring harness connection is loose or bad or if the speedometer cable is jerky and needs to be lubed. "
Now I don't think the speedo cable needs to be lubed in our case as it's probably electronic. Somebody help me out on this one, isn't there a seperate speed sensor that the trans uses for it's reference? I really think we're on to something here.
Driver School Candidate
Joined: Nov 2019
Posts: 1
Likes: 0
From: Texas
I know
Fred, here is a description of my problem and what led me to believe it is the VSS.
I pulled the following after searching on google. This is for another car - maybe GM, but who cares I think this may be the answer to our problems. Looks like it may be the speed sensor. See my comments after the excerpt.
Excerpt form site:
http://www.salemboysauto.com/faqs/d...?Action=Q&ID=28
" 2. As your are driving down the road, the computer is watching your throttle pressure, your engine speed, your vehicle speed in mph, what gear you are in and a/c operation. As you approach 38-42 mph, if you are on level ground, if you are feathering the throttle, if the engine is warmed up, if the car is in third gear, the computer will electronically lock up the torque converter inside the transmission which makes you have direct drive, so to speak.
On this day, the driver brings the car into a shop and complains the engine is bucking and missing . What is happening is the computer sees your throttle pressure stay at 32%, sees the engine rpms stable, but sees the reported speed at 36 then a second later the computer sees 43, then 38, then 41, then 37. The computer would be confused. How can the speed be fluctuating and the engine isn’t and the drivers throttle pressure isn’t changing either? As the speed is reported above 38 mph, the torque converter clutch (TCC) is locked and when the speed is seen below 38 mph, the computer unlocked and disengages the TCC. This rapid locking and unlocking of the TCC feels EXACTLY like an engine miss to the driver. But the computer THINKS the speed sensor is going wacky so it will set the SES light to tell the driver that it sees something wrong.
In this case, the speed sensor was replaced by 3 different shops, except the SES light kept coming on, the same speed sensor code was set and the engine bucked or missed violently when the speed approached 38 to 42 mph. Clearly, the speed sensor wasn’t the problem.
In this case, what finally fixed this car was when we pulled the speedo cable and lubed it. You see when the computer saw the speed vary, it was because the speedo cable was binding up, then releasing causing the speed sensor to report this "speed up, slow down" or 38-41-36-42-34-39 speed reading. Each time the reported speed exceeded 38 the TCC was locked, each time it dropped below 38, the TCC was unlocked causing the bucking or missing. You see, the computer can only guess on the repair, it really can not tell the tech if the speed sensor is bad or the wiring harness connection is loose or bad or if the speedometer cable is jerky and needs to be lubed. "
Now I don't think the speedo cable needs to be lubed in our case as it's probably electronic. Somebody help me out on this one, isn't there a seperate speed sensor that the trans uses for it's reference? I really think we're on to something here.
I pulled the following after searching on google. This is for another car - maybe GM, but who cares I think this may be the answer to our problems. Looks like it may be the speed sensor. See my comments after the excerpt.
Excerpt form site:
http://www.salemboysauto.com/faqs/d...?Action=Q&ID=28
" 2. As your are driving down the road, the computer is watching your throttle pressure, your engine speed, your vehicle speed in mph, what gear you are in and a/c operation. As you approach 38-42 mph, if you are on level ground, if you are feathering the throttle, if the engine is warmed up, if the car is in third gear, the computer will electronically lock up the torque converter inside the transmission which makes you have direct drive, so to speak.
On this day, the driver brings the car into a shop and complains the engine is bucking and missing . What is happening is the computer sees your throttle pressure stay at 32%, sees the engine rpms stable, but sees the reported speed at 36 then a second later the computer sees 43, then 38, then 41, then 37. The computer would be confused. How can the speed be fluctuating and the engine isn’t and the drivers throttle pressure isn’t changing either? As the speed is reported above 38 mph, the torque converter clutch (TCC) is locked and when the speed is seen below 38 mph, the computer unlocked and disengages the TCC. This rapid locking and unlocking of the TCC feels EXACTLY like an engine miss to the driver. But the computer THINKS the speed sensor is going wacky so it will set the SES light to tell the driver that it sees something wrong.
In this case, the speed sensor was replaced by 3 different shops, except the SES light kept coming on, the same speed sensor code was set and the engine bucked or missed violently when the speed approached 38 to 42 mph. Clearly, the speed sensor wasn’t the problem.
In this case, what finally fixed this car was when we pulled the speedo cable and lubed it. You see when the computer saw the speed vary, it was because the speedo cable was binding up, then releasing causing the speed sensor to report this "speed up, slow down" or 38-41-36-42-34-39 speed reading. Each time the reported speed exceeded 38 the TCC was locked, each time it dropped below 38, the TCC was unlocked causing the bucking or missing. You see, the computer can only guess on the repair, it really can not tell the tech if the speed sensor is bad or the wiring harness connection is loose or bad or if the speedometer cable is jerky and needs to be lubed. "
Now I don't think the speedo cable needs to be lubed in our case as it's probably electronic. Somebody help me out on this one, isn't there a seperate speed sensor that the trans uses for it's reference? I really think we're on to something here.
92sc420, is that the only abnormal behavior your speedometer is exhibiting?
If your car is stock and it is doing this it could be the speedo motor behind the visible needle that is malfunctioning. Usually this manifests as a "slow" speedo needle or one that just sticks at 0 MPH until you slap the dash a couple of times to get it to respond again. Those can be fixed by Tanin Auto IF that is the case.
If your car is stock and it is doing this it could be the speedo motor behind the visible needle that is malfunctioning. Usually this manifests as a "slow" speedo needle or one that just sticks at 0 MPH until you slap the dash a couple of times to get it to respond again. Those can be fixed by Tanin Auto IF that is the case.
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