Speedometer cutting in and out (Wiring problem)

[Chayton]

Hey all,


My speedo started cutting in and out the other day. the needle jumps from 60-0-10-40-60-0-60-0 etc. I thought it was the speed sensor and changed it. But the problem came back. it is intermittent. It does eventually go away but usually comes back after a bump or sharp turn. Almost positive it is a wiring problem. Has anyone had this issue? any particular areas I should check? I have had a lot of trouble with the wiring bundle that runs across the front passenger frame rail. I have a feeling its there...just wondering if theres any other spots I should check.

[BAD MERC]

Would be nice to have a spare cluster to use as a control. It is electronic. Does it affect the cruise control? Check the harness and connections at the cruise anyway. The speed pulse wire is gray/black at the cruise, behind the cluster and in the radio harness. Testing it with a VOM and driving to see if the readout mimics the speedometer needle might be the first place to try.

[Chayton]

Here is a picture of the bundle in question (this is taken with the car on jack stands, laying under neath looking up just in front of the passenger wheel, above the fog light)

Would anyone happen to have access to wiring diagram for this bundle? or maybe know what wires are in there? Im hoping this is where the issue is. But im not sure if the speed sensor wiring runs through this bundle. You can see where ive wedged something between the bundle and frame as a temporary insulator. that is where it is rubbing.

http://i.imgur.com/Yf0wnXF.jpg

[Chayton]

been doing some digging.. seems crown vic guys have had this problem. Read a thread where they suggested it could be the speed sensor on differential? someone even suggested changing the fluid lol. Once I get off work I will begin the process of elimination

[mm svt]

The speedo sensor is in the transmission harness try checking the connection there see if fluid has gotten into it

[Chayton]

The speedo sensor is in the transmission harness try checking the connection there see if fluid has gotten into it

will do!!!!

[Chayton]

Update: problem fixed


Began my process of elimination...there was a CEL code stored for speed sensor error. Check transmission harness and all connectors. Looked good. Upon further inspection the main wiring harness connector under the hood below brake booster (one held together with nut/bolt) was loose. Tightened her up and problem has been eliminated!!!'

[Chayton]

Update: I lied. It's doing it again.

[Chayton]

Any ideas...Wiring at the speed sensor looked OK. Ill have to look again. Anywhere else I should check? connection at PCM? behind Speedometer? So frustrating. I did tug on the trans wiring harness yesterday to make sure it wasnt caught anywhere. That seemed to fix the problem temporarily. But could also be placebo. Im not sure. Does anyone have access to a complete vehicle wiring diagram?

[mm svt]

http://www.revbase.com/BBBMotor/Wd

This link was posted back when I was looking for the pin out. It's very useful.

[Chayton]

http://www.revbase.com/BBBMotor/Wd

This link was posted back when I was looking for the pin out. It's very useful.

Thanks man. Much appreciated!

[Chayton]

I was able to fix it by going under the car and tugging on the trans harness that goes up and over transmission. maybe it was pinched somewhere. Seems to be working good now...!

[RF Overlord]

Try spraying some electrical contact cleaner (or MAF cleaner) into both sides of the connectors for the OSS and the DTRS. According to the wiring manual, the OSS feeds from the PCM, through the DTRS and back to the PCM.

[mm svt]

Good news Chayton

[Chayton]

Try spraying some electrical contact cleaner (or MAF cleaner) into both sides of the connectors for the OSS and the DTRS. According to the wiring manual, the OSS feeds from the PCM, through the DTRS and back to the PCM.

will do. THX guys!