troubleshooting 1996 Ford Ranger

[Clare Snyder]

I realize this forum is virtually dead but I am hoping there are still
a fewe Ford Experts still monitoring.

I have a 1996 Ford Ranger 4.0 5 speed longbox standard cab 2 wheel
drive truck with no power windows. mirrors or locks. The speedometer
has recently stopped working and I have found something that does NOT
make any sense. with the ecu plug connected or disconnected and the
engine-cab connector connected I get a DC voltage reading of about 8.5
volts with the key off, rising to 12 volts with the engine running,
and at the same time an AC voltage - cannot remember the base when not
running, but rizing to 15+ volts with the engine running. When I
disconnect the harness to the cab the voltage goes away. The speed
censor gives me about 2.6 volts AC when spun by my Milwaukee battery
drill and the signal can be read between pins 33 and 58 on the ecu -
either connected or disconnected - as long as the cab harness is
disconnected In the wiring diagrams the only thing these wires connect
to in the cab are the speedo and the CTM / GEM. It would also connect
to the speed controller amplifier/servo assembly if the truck had
cruise control (which it does not) Pulling every fuse, one at a time,
from the fuse panel in the end of the dash panel does NOT kill either
the AC or DC voltage across the speed sensor. Is there any function or
misfunction of the CTM/GEM on this vehicle that could/would feed
either an AC oe DC voltave bact to the ECU/speed sensor circuit????

[Clare Snyder]

Post by Clare Snyder
I realize this forum is virtually dead but I am hoping there are still
a fewe Ford Experts still monitoring.
I have a 1996 Ford Ranger 4.0 5 speed longbox standard cab 2 wheel
drive truck with no power windows. mirrors or locks. The speedometer
has recently stopped working and I have found something that does NOT
make any sense. with the ecu plug connected or disconnected and the
engine-cab connector connected I get a DC voltage reading of about 8.5
volts with the key off, rising to 12 volts with the engine running,
and at the same time an AC voltage - cannot remember the base when not
running, but rizing to 15+ volts with the engine running. When I
disconnect the harness to the cab the voltage goes away. The speed
censor gives me about 2.6 volts AC when spun by my Milwaukee battery
drill and the signal can be read between pins 33 and 58 on the ecu -
either connected or disconnected - as long as the cab harness is
disconnected In the wiring diagrams the only thing these wires connect
to in the cab are the speedo and the CTM / GEM. It would also connect
to the speed controller amplifier/servo assembly if the truck had
cruise control (which it does not) Pulling every fuse, one at a time,
from the fuse panel in the end of the dash panel does NOT kill either
the AC or DC voltage across the speed sensor. Is there any function or
misfunction of the CTM/GEM on this vehicle that could/would feed
either an AC oe DC voltave bact to the ECU/speed sensor circuit????

In case there is anybody on here, I found the problem. There was a
short INSIDE the connector between the body/chassis harness and the
engine harness, shorting the 12 volts constant power from the ECU
Memory/horn fuse under the hood to the VSS signal wire - they are next
to each other in the connector. NO visible damage or indication.
Trust me, it was one HELL of a job tracing this one down!!!!!!!
Ended up cutting the vss wire from the plugs and adding an external
connection.

[John Keiser]

Post by Clare Snyder

Post by Clare Snyder
I realize this forum is virtually dead but I am hoping there are still
a fewe Ford Experts still monitoring.
I have a 1996 Ford Ranger 4.0 5 speed longbox standard cab 2 wheel
drive truck with no power windows. mirrors or locks. The speedometer
has recently stopped working and I have found something that does NOT
make any sense. with the ecu plug connected or disconnected and the
engine-cab connector connected I get a DC voltage reading of about 8.5
volts with the key off, rising to 12 volts with the engine running,
and at the same time an AC voltage - cannot remember the base when not
running, but rizing to 15+ volts with the engine running. When I
disconnect the harness to the cab the voltage goes away. The speed
censor gives me about 2.6 volts AC when spun by my Milwaukee battery
drill and the signal can be read between pins 33 and 58 on the ecu -
either connected or disconnected - as long as the cab harness is
disconnected In the wiring diagrams the only thing these wires connect
to in the cab are the speedo and the CTM / GEM. It would also connect
to the speed controller amplifier/servo assembly if the truck had
cruise control (which it does not) Pulling every fuse, one at a time,
from the fuse panel in the end of the dash panel does NOT kill either
the AC or DC voltage across the speed sensor. Is there any function or
misfunction of the CTM/GEM on this vehicle that could/would feed
either an AC oe DC voltave bact to the ECU/speed sensor circuit????

In case there is anybody on here, I found the problem. There was a
short INSIDE the connector between the body/chassis harness and the
engine harness, shorting the 12 volts constant power from the ECU
Memory/horn fuse under the hood to the VSS signal wire - they are next
to each other in the connector. NO visible damage or indication.
Trust me, it was one HELL of a job tracing this one down!!!!!!!
Ended up cutting the vss wire from the plugs and adding an external
connection.

What clues allowed you to find the short?