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Discussion Starter · #1 ·
Hello guys, I have an early 99 f250, auto, 170k, rwal, and my speedo works intermittently. I replaced the vss, the tone ring seems good upon inspection while changing the rear diff fluid, so I replaced the plug for the vss to the frame rail, and I thought I had a short there. What I'm looking for is help with where the wires go from there? I will check them with my fluke, but was tempted to change them out all together, rerun wires for them, but I'm not sure where they go to. Do they go to the rwal valve, or to the gem, pcm? The ford tech had his computer on it, and the vss does a signal to the gem, but it's very sporadic, and looks more like an heart rate at the hospital, than the actual speed of the vehicle. My abs light is on, the od light flashes on my shifter, until it rains, then it sends to work just dandy. He told me he's certain is a wiring issue, but I'm liking for direction from you guys as you where I need to check.
Thank you in advance for any help
 

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You need to create a signature with more information about your truck. This helps others help you! I will assume this is a 1999 Heavy Duty truck, 7.3L Diesel, E4OD transmission... or something like that.

The VSS circuits are in the main wiring loom headed all the way forward in the left side frame rail. It ends up at the ABS module connector C1040, Pins 9 (R/PK) and 21 (LG/BK) The ABS module is bolted to the HCU at the front of the left frame rail - might need to remove the wheel well to access it. There is a connector in between the sensor and ABS module, connector C1046 located on the left side front wheel well below the brake master cylinder. The rest of the modules get the VSS data through the network so your best bet is to test and inspect the two VSS circuits.

Happy Hunting!
 
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Discussion Starter · #3 ·
Thank you very much! and your assumption on my truck is right, but I'll fix that, do it's not an issue going forward.
 

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In your sig, specify if it's 2WD or 4WD ABS. Check the ABS sensor wiring at the wheels. Strange that it's OK when raining.
 
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Discussion Starter · #5 · (Edited)
I wrote in my original post that it's rwal, do just rear wheel abs, but I was having issues getting my Sig to show, on a side note anyway. But it sends good now
 

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Discussion Starter · #6 ·
I found it guys, the ground in front of the drivers battery was broken inside the case, pretty much right under the battery. When I was testing for continuity through all the wires, I found that wiggling the ground, showed the problem. Replaced the wire, all better now
Thanks for the help!
 
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