Service manual

Symptom Possible Problem Solution
-----------------------------------------------------------------------------------------------------------------------------------
The tachometer reading The tachometer signal wire is Check the connections at both
is incorrect. loose or broken. ends of the wire.
The control box is not set up for Refer to the Internal Adjustments
the proper number of cylinders section of the installation manual
or the proper tach range. to set the control box properly.
The speedometer will The speed sending unit is not Check that both speed sending
not show a reading. connected to the control box unit wires are connected to the
properly. control box properly.
The speed sending unit is not Check that sender is mounted
connected to the transmission properly.
properly. Check that transmission has the
appropriate internal parts.
The sending unit wire is picking Isolate the sending unit wire from
up noise from nearby wires. motor and ignition wires.
The vehicle speed buffer is not Check the stock VSS buffer according
working correctly. to the GM service manual.
The fuel display reads The control box may be set for Refer to the Internal Adjustments
backwards, incorrectly, the wrong type of fuel sender. section of the installation manual
or does not change. to ensure that the settings match
your fuel sender.
The fuel sender may not be Check the connections at both
connected to the control box ends of the fuel sender wire.
properly. Make sure the fuel sender is
grounded properly.
The fuel sender may not be Check the fuel sending unit with
operating properly. a mechanical gauge or an
electrical multi-meter.
The fuel sender may have a If the proper resistance range
non-standard resistance setting is not available with
range. the control box settings, replace
the fuel sender with a different
style.
The oil or water display The engine block may not be Use heavy ground cables from the
reading is incorrect. grounded to the chassis frame battery to the engine block.
or body properly. Make sure both ends of the cable
have clean metal-to-metal
connections.
Use a braided ground strap to
ground the engine block to the
chassis.
Use a large braided ground strap
to ground the engine block to
the body or fire wall.
The sending unit wire is picking Isolate the sending unit wire from
up noise from nearby wires. motor and ignition wires.
The sending unit is not Use the appropriate GM gauge
compatible with the control box sending unit.
The sending unit has failed. Replace the sending unit