Brian1
Elite Explorer
- Joined
- February 2, 2000
- Messages
- 5,387
- Reaction score
- 644
- City, State
- Albuquerque, NM
- Year, Model & Trim Level
- 1991 XLT
- Callsign
- KG5BAQ
1991 Explorer, manual trans, 4x4.
In tracking down some running issues with my engine I kept getting a memory Code 29 insufficient input from the vehicle speed sensor. I would clear the memory code and it would always come back. Also it would not give a speed reading on my code scanner, it would stay at 0 mph. I read up on here and a google search and found the problem to be related to the ECU.
First I tested the VSS sensor, it is supposed to have 180-250 ohms of resistance between the 2 pins. Mine had 200 and the one in my old transfer case I have in my backyard has 201. That checks out.
Next I did a wire continuity test from the vss harness at the t-case to the computer. Pins 3 and 6 are the VSS signal inputs. Both wires checked out and each had under 1 ohm of resistance. I read the spec was 5 ohms but I don't think this should be an issue.
My speedometer reads smoothly most of the time and only has a few very small flutters on occasion.
I had another 91 4x4 manual trans computer on hand that I swapped in and here is what I don't understand: With the new (used) computer the VSS works and the code is gone as well as I get a speed reading on my scanner. Is it possible that just the VSS circuit in the computer is fried? My old computer seemed to be functioning fine as there was no change when I swapped to the spare computer other than the VSS started working.
Thoughts? Engine problem seems to be cured but this issue still remains.
In tracking down some running issues with my engine I kept getting a memory Code 29 insufficient input from the vehicle speed sensor. I would clear the memory code and it would always come back. Also it would not give a speed reading on my code scanner, it would stay at 0 mph. I read up on here and a google search and found the problem to be related to the ECU.
First I tested the VSS sensor, it is supposed to have 180-250 ohms of resistance between the 2 pins. Mine had 200 and the one in my old transfer case I have in my backyard has 201. That checks out.
Next I did a wire continuity test from the vss harness at the t-case to the computer. Pins 3 and 6 are the VSS signal inputs. Both wires checked out and each had under 1 ohm of resistance. I read the spec was 5 ohms but I don't think this should be an issue.
My speedometer reads smoothly most of the time and only has a few very small flutters on occasion.
I had another 91 4x4 manual trans computer on hand that I swapped in and here is what I don't understand: With the new (used) computer the VSS works and the code is gone as well as I get a speed reading on my scanner. Is it possible that just the VSS circuit in the computer is fried? My old computer seemed to be functioning fine as there was no change when I swapped to the spare computer other than the VSS started working.
Thoughts? Engine problem seems to be cured but this issue still remains.
