Originally Posted by GMCummins
My overhead computer is not working, all the lights are on, and it will read the direction, ie N S E W, but I cant get any readings for MPG, DTE, etc..what might cause this and where would i start looking..
thanks for any input.
This is out of the 2001 service manual. It may help you find out whats up.
A self-diagnostic test is used to determine that the
compass mini-trip computer module is operating
properly electrically. Initiate the self-diagnostic test
(1) With the ignition switch in the Off position,
simultaneously depress and hold the Step button and
the U.S./Metric button.
(2) Turn the ignition switch to the On position.
(3) Continue to hold both buttons depressed until
the compass mini-trip computer module enters the
display segment test. In this test, all of the Vacuum
Fluorescent Display (VFD) segments are lighted
while the compass mini-trip computer module performs
the following checks:
² Microprocessor RAM read/write test
² Non-volatile memory read/write test
² Microprocessor ROM verification test
² CCD communications test.
(4) Following completion of these tests, the compass
mini-trip computer will display one of three
messages: “PASS,” “FAIL,” or “CCd.” Respond to the
respective test results as follows:
² If the “PASS” message is displayed, but compass
mini-trip computer operation is still improper, the
use of a DRB scan tool and the proper Diagnostic
Procedures manual are required for further diagnosis.
² If the “FAIL” message is displayed, the compass
mini-trip computer module is faulty and must be
² If the “CCd” message is displayed, the use of a
DRBt scan tool and the proper Diagnostic Procedures
manual are required for further diagnosis.
² If any VFD segment should fail to light during
the display segment test, the compass mini-trip computer
module is faulty and must be replaced.
(5) If all tests are passed, or if the ignition switch
is turned to the Off position, the compass mini-trip
computer module will automatically return to normal