How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Jeromy Madison Your Own Question
Jeromy Madison
Jeromy Madison,
Category: Ford
Satisfied Customers: 71
Experience:  Owner/Technician at Mad Auto Repair
90693043
Type Your Ford Question Here...
Jeromy Madison is online now
A new question is answered every 9 seconds

Im having trouble with speedo getting a reading

Customer Question

Hi im having trouble with speedo getting a reading
Submitted: 1 year ago.
Category: Ford
Expert:  Jeromy Madison replied 1 year ago.

Can you tell me a little more?

Customer: replied 1 year ago.
Abslight is n no speed reading and o/d light flashing
Expert:  Jeromy Madison replied 1 year ago.

Did you say that you have replaced the vss sensor?

Customer: replied 1 year ago.
I tested it by jacking up rear axle and put in drive and with a meter I tested voltage and as wheel speed increased the voltage did
Expert:  Jeromy Madison replied 1 year ago.

That is the correct test. You will need to test the continuity of the wires from the sensor to the pcm. There might be damage somewhere.

Customer: replied 1 year ago.
Should their be any voltage b coming from pcm with key on at the plug?
Expert:  Jeromy Madison replied 1 year ago.

Here is a wiring diagram. You see it runs to the abs control module, and that could be the issue. That sensor creates its own voltage, so it should not get voltage from the pcm.

Let me know if I can help anymore.

Expert:  Jeromy Madison replied 1 year ago.

That might not open. Try this one.

Customer: replied 1 year ago.
It was reading .003 on ac
Customer: replied 1 year ago.
Also mine is a 7.3L
Customer: replied 1 year ago.
Is the wire coming from the pcm a ground or hot wire?
Customer: replied 1 year ago.
Ok so I decided to do a test and when I put it in gear and let it get to be about 95-100 mph the speed starts to register
Expert:  Jeromy Madison replied 1 year ago.

If it did, then I would suggest replacing the sensor and see if that fixes it.

Customer: replied 1 year ago.
I had an extra axle with sensor that I knew worked and after I did that there was no respond
Expert:  Jeromy Madison replied 1 year ago.

Ok. The wiring of the 6.8L and the 7.3L are the same. The wire going to the pcm from the ABS module is just a signal not a ground. It still appears that the ABS module is most likely the cause. You could check the voltage coming out of the ABS to see if it sending a signal to the pcm.

Customer: replied 1 year ago.
What is the voltage that is supposed to be coming from the abs
Expert:  Jeromy Madison replied 1 year ago.

Ok, lets go back to the beginning. Can you do a resistance test across the vss terminals? It should be between 170 to 270 ohms.

Customer: replied 1 year ago.
Its bouncing around but its getting a 2.007 then drop to 1. Something then goes to 0.L
Expert:  Jeromy Madison replied 1 year ago.

Are you reading ohm? Make sure the sensor is disconnected and check across the terminals. If it is out of spec. it should be replaced according to the service manual.