Mechanics

F350 SPEEDOMETER

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.
Avatar
Newtc84
June 18, 2007.



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.

Tiny
Newtc84
Jun 19, 2007.
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?

Tiny
Newtc84
Jun 20, 2007.
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?

Tiny
Newtc84
Jun 20, 2007.
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.

Tiny
Newtc84
Jun 20, 2007.
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?

Tiny
Newtc84
Jun 20, 2007.
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?

Tiny
Newtc84
Jun 20, 2007.
Is there any way to test the wires in different spots to try and pinpoint where I am losing the signal?

Tiny
Newtc84
Jun 20, 2007.
Thank you very much for your help! This problem has given even the best shops in my city a tough time. Thanks again.

Tiny
Newtc84
Jun 20, 2007.
Not yet. I think I am going to work on it tomorrow. I'll let you know when I find it.

Tiny
Newtc84
Jun 21, 2007.
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?

Tiny
Newtc84
Jun 21, 2007.
Page 1 of 3