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Speedometer does not work?

Tiny
BILLIE BROWN
  • MEMBER
  • 2006 FORD F-350
  • V8
  • 4WD
  • AUTOMATIC
  • 36,000 MILES
This is a diesel. The speedometer floats and usually ends on 100 mph. I assume it is a sensor. Do you think a unexperienced person can replace the sensor if I had a picture (diagram)
Saturday, January 19th, 2008 AT 11:38 AM

44 Replies

Tiny
FLEXY5
  • MECHANIC
  • 512 POSTS
I see you posted the vehicle as only having 36,000 mile on it. Is it slightly over 36,000? Most people don't know this (hush, hush) but if the vehicle falls within a certain time period after the 3 yr/36,000 warranty, your local dealer may do something called an "after warranty adjustment." This problem could possibly be a sensor. It would be the one mounted to the top of the rear differential. But my suggestion would be: if you can have it done with little or no cost to you, it's worth the phone call. If it is not the sensor, it may well be either the main computer or the instrument cluster. Play dumb when you call and ask if there is any way they can help since it is just outside of the warranty. See what they say, you may be suprised!
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Saturday, January 19th, 2008 AT 12:34 PM
Tiny
NEWTC84
  • MEMBER
  • 38 POSTS
  • 2000 FORD F-350
I have a 2000 F350 Diesel that had a good speedometer when I bought it. Shortly after, it stopped working. With the speedo wne the odometer and the cruise. The OD light is flashing. When I had it plugged in I got the code for vehicle speed sensor, but I had those replaced and nothing still. I took it back in and they said the problem is the signal from the speed sensors is getting lost somewhere between the abs module and the PCM. They checked the abs system and it had no codes or problems. So does that mean my PCM is bad? Also, the speedo comes on from time to time, then goes out again. Also, if it is the PCM, where is that located so I can take it out and have it tested? Thanks.
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Saturday, August 8th, 2020 AT 11:40 AM (Merged)
Tiny
NEWTC84
  • MEMBER
  • 38 POSTS
Okay, I disconnected the wires from the front of the master cylinder reservoir. When I drove it everything was the same, no speedo, etc. Only difference was the brake light on the dash was illuminated.
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Saturday, August 8th, 2020 AT 11:40 AM (Merged)
Tiny
NEWTC84
  • MEMBER
  • 38 POSTS
Okay, I measured the terminals with the wires disconnected from the reservoir. I am not sure if I am doing it right, but I was measuring on D/C, and A/C in volts and the reading I got was 3.5 to 3.6 volts in D/C and in A/C it was around 4.2 volts. Is that the number you wanted? Also, the vehicle is 2wd, and I believe it is only rear ABS. It is the basic XL model with no options, so I would not think it has 4 wheel anti lock. Is there any way to know for sure?
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Saturday, August 8th, 2020 AT 11:40 AM (Merged)
Tiny
NEWTC84
  • MEMBER
  • 38 POSTS
Hello, I found out how to test resistance which is what you asked for. The reading I got was 6.00, however the setting was set to 20K ohms. So I am assuming that means the reading I got was 6000 ohms? I am not sure how these work, but that is what I think. What would you like me to do next?
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Saturday, August 8th, 2020 AT 11:40 AM (Merged)
Tiny
NEWTC84
  • MEMBER
  • 38 POSTS
Hello, Sorry I was not sure what you wanted before. I just measured with the Ohms set at 2000 across the speed sensor terminals, with the sensor out of the truck and the reading was 1.997. I will stay close to the computer now. I was not expecting such a quick response. Thank you.
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-1
Saturday, August 8th, 2020 AT 11:40 AM (Merged)
Tiny
NEWTC84
  • MEMBER
  • 38 POSTS
Okay, I tested the sensor at 200 ohms and it just gave me a reading of 1, meaning the reading was higher than the setting. At 2000 ohms setting I got readings of 1.997. Yes I inspected the wires and the terminal and found that they looked good. The wires were red, and green with a black stripe. What would you like me to do next?
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Saturday, August 8th, 2020 AT 11:40 AM (Merged)
Tiny
NEWTC84
  • MEMBER
  • 38 POSTS
I tested the two wires that lead back to the sensor at the fender. It gave me no reading at all. I was still on 2000 ohms and there was no reading. Does that mean I have faulty wires somewhere between the sensor and that connection?
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Saturday, August 8th, 2020 AT 11:40 AM (Merged)
Tiny
NEWTC84
  • MEMBER
  • 38 POSTS
Is there any way to test the wires in different spots to try and pinpoint where I am losing the signal?
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Saturday, August 8th, 2020 AT 11:40 AM (Merged)
Tiny
NEWTC84
  • MEMBER
  • 38 POSTS
Thank you very much for your help! This problem has given even the best shops in my city a tough time. Thanks again.
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Saturday, August 8th, 2020 AT 11:40 AM (Merged)
Tiny
NEWTC84
  • MEMBER
  • 38 POSTS
Not yet. I think I am going to work on it tomorrow. I'll let you know when I find it.
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Saturday, August 8th, 2020 AT 11:40 AM (Merged)
Tiny
NEWTC84
  • MEMBER
  • 38 POSTS
Hello again,
I made a mistake yesterday. I had the meter at the wrong setting. I tried again today at the correct setting and I tested the harness at the fender, it gave me the same reading that I got from the sensor. So the wiring is giving a good signal up to that point. Sorry about that. I need to continue testing. What is the next step?
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Saturday, August 8th, 2020 AT 11:40 AM (Merged)
Tiny
NEWTC84
  • MEMBER
  • 38 POSTS
I removed the driver side battery and pan that it sits in. Is the ABS module silver and has the brake lines going into it? I can not see any wires going into it. What wires am I going to be testing? Can you explain?
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Saturday, August 8th, 2020 AT 11:40 AM (Merged)
Tiny
NEWTC84
  • MEMBER
  • 38 POSTS
Never mind, I was able to access the wires from underneath the fender well. I will test the same two wires now.
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Saturday, August 8th, 2020 AT 11:40 AM (Merged)
Tiny
NEWTC84
  • MEMBER
  • 38 POSTS
I found the wires. I had to access them from underneath, not from the top. I tested them at the plug. Same reading as before. Now the next step requires 2 people right? Lift the rear wheels off the ground, make a nick in the black/grey wire at the ABS module, then turn meter to low ac volts, and have someone turn the rear wheels as fast as they can, right? Making sure the black lead goes to ground and the red to the black, grey wire. With the ABS module plugged back in.
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Saturday, August 8th, 2020 AT 11:40 AM (Merged)
Tiny
NEWTC84
  • MEMBER
  • 38 POSTS
Does it matter which rear wheel is spun? And which direction? Also, the ground lead from the meter means just touching it to metal, right? Just want to make sure I do it right.
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Saturday, August 8th, 2020 AT 11:40 AM (Merged)
Tiny
NEWTC84
  • MEMBER
  • 38 POSTS
I had someone spinning the rear wheels while I tested the wires. I had the meter set at 200mV. The initial readings I was getting were around 10.0. As the wheels were turned the readings went up to around 25.0. What is the next step?
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Saturday, August 8th, 2020 AT 11:40 AM (Merged)
Tiny
NEWTC84
  • MEMBER
  • 38 POSTS
Hello, I'm sorry I don't really understand the last instructions totally. The instrument cluster meaning all of the guages from the dash? Then I don't really understand where to put the two lead ends? One at the wheelwell, and the other where? I can't quite picture what you want for me to do.
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Saturday, August 8th, 2020 AT 11:40 AM (Merged)
Tiny
NEWTC84
  • MEMBER
  • 38 POSTS
Okay, I got the instrument cluster out and I found the black/grey wire. It is firmly connected. Now, could you walk me through how to test the integrity of the wire again, please?
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Saturday, August 8th, 2020 AT 11:40 AM (Merged)
Tiny
NEWTC84
  • MEMBER
  • 38 POSTS
Okay, I got it. I did that and I got the same reading, showing consistency through the wire. So, you said that means I have a bad cluster?
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Saturday, August 8th, 2020 AT 11:40 AM (Merged)

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