Has anyone ever run into this: Today after I started my truck up at the grocery store, apparently the computer/sensor that takes readings for the fuel stats/temperature stuff malfunctioned, the sensor only displayed '--'. The compass was working fine. Once I got to a stop light I turned my truck off and back on, and the sensors came back. Anyone know what this could have been?

 

You can run the diagnostic on it to see if it picks up on anything. There is alot here but hopefully some of this will help you.

From my 02 service manual:

DIAGNOSIS AND TESTING - OVERHEAD
CONSOLE
If the problem with the overhead console is an
inaccurate or scrambled display, refer to Self-Diagnostic
Test below. If the problem with the overhead
console is incorrect Vacuum Fluorescent Display
(VFD) dimming levels, use a DRB IIIt scan tool and
the proper Diagnostic Procedures manual to test for
the correct dimming message inputs being received
from the Body Control Module (BCM) or Front Control
Module (FCM) over the J1850 Programmable
Communications Interface (PCI) data bus circuit. If
the problem is a no-display condition, use the following
procedures. For complete circuit diagrams, refer
to Overhead Console in the Wiring Diagrams section
of the service manual.
(1) Remove the overhead console from the headliner.
Refer to the procedure later in this section.
(2) Check for battery voltage at the overhead console
electrical connector. Refer to Wiring for connector
information. If OK, go to Step 3. If not OK, Check
for battery voltage at the appropriate B(+) fuse in the
integrated power module, repair the open fused B(+)
circuit as required.
(3) Turn the ignition switch to the On position.
Check the fused ignition switch output circuit(s) at
the overhead console electrical connector. If OK, go to
Step 4. If not OK, repair the open or shorted circuit
as required.
(4) Turn the ignition switch to the Off position.
Disconnect and isolate the battery negative cable.
Check for continuity between the ground circuit cavity
of the overhead console electrical connector and a
good ground. There should be continuity. If OK, refer
to Self-Diagnostic Test below for further diagnosis
of the electronics module and the J1850 PCI data bus
circuit. If not OK, repair the open ground circuit as
required.

SELF-DIAGNOSTIC TEST
A self-diagnostic test is used to determine that the
electronics module is operating properly, and that all
the J1850 PCI data bus messages are being received
for initial operation. Initiate the self-diagnostic test
as follows:
(1) With the ignition switch in the Off position, on
Electronic Vehicle Information Center (EVIC) and
Compass Mini-Trip Computer (CMTC) equipped vehicles
simultaneously depress and hold the STEP and
the RESET buttons.
(2) Turn the ignition switch to the On position.
(3) Following completion of these tests, the electronics
module will display one of the following messages:
a. Pass Self Test (EVIC only), PASS (CMTC) -
The electronics module is working properly.
b. Failed Self Test (EVIC only), FAIL (CMTC) -
The electronics module has an internal failure. The
electronics module is faulty and must be replaced.
c. Failed J1850 Communication (EVIC only),
BUS (CMTC) - The electronics module is not receiving
proper message input through the J1850 PCI
data bus circuit. This can result from one or more
faulty electronic modules in the vehicle, or from a
faulty PCI data bus. The use of a DRB IIIt scan tool
and the proper Diagnostic Procedures manual are
required for further diagnosis.
NOTE: If the compass functions, but accuracy is
suspect, it may be necessary to perform a variation
adjustment. This procedure allows the compass
unit to accommodate variations in the earth’s magnetic
field strength, based on geographic location.
Refer to Compass Variation Adjustment in the Service
Procedures section of this group.
8M - 2 MESSAGE SYSTEMS DR
OVERHEAD CONSOLE

(Continued)

COMPASS/MINI-TRIP
COMPUTER
DESCRIPTION
The Compass Mini-Trip Computer (CMTC) is a
module located in the overhead console. The CMTC is
equipped with a mini-trip feature. The CMTC consists
of a electronic control module with a vacuum
fluorescent display (VFD) and function switches. The
CMTC consists of a electronic module that displays
compass, trip computer, and temperature features.
Actuating the STEP push button will cause the
CMTC to change mode of operation when ignition is
ON. Actuating the STEP push button will cause the
CMTC to change mode of operation when ignition is
ON. Example:
² Average miles per gallon (ECO)
² Distance to empty (DTE)
² Instant miles per gallon (ECO)
² Trip odometer (ODO)
² Elapsed time (ET)
² Off
Actuating the C/T push button will cause the
CMTC to change to Compass/Temperature display.
OPERATION
The Compass Mini-Trip Computer module in the
overhead console has buttons used to select various
functions. The CMTC selector buttons will not operate
until the ignition is in the RUN position.
When the ignition switch is first turned to the
RUN position the CMTC display;
² Returns to the last mode setting selected before
the ignition was last switched OFF.

DIAGNOSIS AND TESTING - COMPASS
MINI-TRIP COMPUTER
Compass Mini-Trip Computer (CMTC) data is
obtained from other electronic modules (CCN, FCM
and JTEC) on the J1850 Data Bus circuit. The
CMTC will display dashes (- -) for any of the screens
it did not receive the bus messages. The label corresponding
to the missing information will be lit. If no
compass mini-trip computer data is displayed, check
the J1850 Data Bus circuit communications and the
other modules. If the brightness level is improper
check the J1850 Data Bus circuit.
Refer to Overhead Console Diagnosis and Testing
for instructions on performing a CMTC module Self-
Diagnostic Test. The DRB IIIt is recommended for
checking the J1850 Data Bus circuit and the other
modules. Perform the CMTC self diagnosis before
replacing the CMTC module.
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Remove overhead console. Refer to Overhead
Console Removal and Installation in this section(Refer
to 8 - ELECTRICAL/OVERHEAD CONSOLE -
REMOVAL).
(3) Remove the screws holding Compass Mini-Trip
Computer module in the overhead console.
(4) Remove CMTC module from console assembly.
INSTALLATION
(1) Position the compass mini-trip computer module
in the overhead console.
(2) Install the screws holding the compass minitrip
computer module in the overhead console.
(3) Install the overhead console (Refer to 8 -
ELECTRICAL/OVERHEAD CONSOLE - INSTALLATION).
(4) Connect the battery negative cable.
NOTE: If a new module has been installed, the compass
will have to be calibrated and the variance set.
Refer to Compass Variation Adjustment and Compass
Calibration in the Service Procedures section
of this group for the procedures.

DIAGNOSIS AND TESTING - ELECTRONIC
VEHICLE INFORMATION CENTER
Electronic Vehicle Information Center (EVIC) data
is obtained from other electronic modules (CCN,
FCM, JTEC) on the J1850 Data Bus circuit. The
EVIC will display dashes (- -) for any of the screens
it did not receive the bus messages. The label corresponding
to the missing information will be lit. If no
EVIC data is displayed, check the J1850 Data Bus
circuit communications and the other modules. If the
brightness level is improper check the J1850 Data
Bus circuit.
Refer to Overhead Console Diagnosis and Testing
for instructions on performing a EVIC module Self-
Diagnostic Test. The DRB IIIt is recommended for
checking the J1850 Data Bus circuit and other modules.
Perform the EVIC self diagnosis before replacing
the EVIC module.

DR MESSAGE SYSTEMS 8M - 7
ELECTRONIC VEHICLE INFO CENTER (Continued)
STANDARD PROCEDURE - ELECTRONIC
VEHICLE INFORMATION CENTER
PROGRAMMING
EVIC PROGRAMMING MODE
Some vehicles are equipped with a Electronic Vehicle
Information Center (EVIC) equipped overhead
console. The Electronic Vehicle Information Center
(EVIC) provides the vehicle operator with a user
interface, which allows the selection of several
optional customer programmable electronic features
to suit individual preferences. The EVIC must be
placed into its programming mode in order to view or
change the programmable features. To enter the
EVIC programming mode and to view or change the
selected programmable features options, proceed as
follows:
(1) Turn the ignition switch to the On position.
(2) Depress and release the Menu push button.
The first item in the programmable features menu
list will appear in the EVIC display.
(3) Momentarily depress and release the Menu
push button to step through the programmable features
list. Each programmable feature and its currently
selected option will appear on the EVIC
display in the sequence shown in the Programmable
Features list that follows.
(4) Momentarily depress and release the Step push
button to step through the available options for the
programmable feature being displayed.
(5) The option that last appears in the display
with a programmable feature before exiting the programming
mode, becomes the newly selected programmable
feature option.
(6) The EVIC exits the programming mode and
returns to its normal operating mode when the C/T
push button is depressed or when the end of the programmable
features menu list is reached, whichever
occurs first.
PROGRAMMABLE FEATURES
² LANGUAGE? - The options include English,
Francaise, Deutsch, Italiana, or Espanol. The default
is English. All EVIC display nomenclature, including
the trip computer functions, warning messages and
the programmable features appear in the selected
language.
² DISPLAY U.S. OR METRIC? - The options
include U.S. and M. The default is U.S. This feature
toggles the trip computer temperature, fuel economy
and odometer display readings between U.S. and
metric units of measure.
² SERVICE INTV. = - The options include from
3200 to 12000 kilometers in 800 kilometer increments
(2000 to 7500 miles in 500 mile increments).
The default is 12000 kilometers (7500 miles). The
selected distance becomes the interval at which the
Perform Service warning message will be displayed
by the EVIC. If a new distance is selected, a second
programmable feature appears, RESET SERVICE
DISTANCE? - The options include No and Yes. The
default is Yes. When Yes is selected, the accumulated
distance since the last previous Perform Service
warning message will be reset to zero because the
service interval has been changed. When No is
selected, the distance until the next Perform Service
warning message is reduced by the accumulated distance
since the last previous message.
² AUTO DOOR LOCKS? - The options include
Yes and No. The default is Yes. When Yes is selected,
all doors lock automatically when vehicle speed
reaches 25 kilometers-per-hour (15 miles-per-hour). If
YES is selected, a second programmable feature
appears, AUTO UNLOCK ON EXIT? - The options
again include Yes and No. The default is No. When
Yes is selected, following each Auto Door Lock event
all doors will automatically unlock when the driver
door is opened, if the vehicle is stopped and the
transmission gear selector is in Park or Neutral. The
Auto Door Unlock event will only occur once following
each Auto Door Lock event.
² REMOTE UNLOCK - The options include
Driver Door 1st and All Doors. The default is Driver
Door 1st. When Diver Door 1st is selected, only the
driver door unlocks when the Unlock button of the
Remote Keyless Entry (RKE) transmitter is
depressed once. The Unlock button of the RKE transmitter
must be depressed twice to unlock all doors.
When All Doors is selected, all doors unlock when the
Unlock button of the RKE transmitter is depressed
once.
² SOUND HORN ON LOCK? - The options
include On and Off. The default is No. When Yes is
selected, a short horn chirp will provide an audible
confirmation when the RKE receiver recognizes a
valid Lock signal from an RKE transmitter. When No
is selected, no horn chirp will occur with the RKE
Lock event. This feature may be selected independent
of the FLASH LIGHTS WITH LOCKS? programmable
feature.
² FLASH LIGHTS WITH LOCKS? - The options
include Yes and No. The default is Yes. When Yes is
selected, a single flash of the hazard warning lamps
will provide an optical confirmation when the RKE
receiver recognizes a valid Lock signal from an RKE
transmitter, and two flashes of the same lamps will
occur when the RKE receiver recognizes a valid
Unlock signal from an RKE transmitter. When No is
selected, no lamp flash will occur with the RKE Lock
or Unlock event. This feature may be selected independent
of the SOUND HORN ON LOCK? programmable
feature.
8M - 8 MESSAGE SYSTEMS DR
ELECTRONIC VEHICLE INFO CENTER (Continued)
² HEADLAMP DELAY = - The options include
Off, 30 Sec, 60 Sec, and 90 Sec. The default is 90 Sec.
When a time interval is selected, the headlamps will
remain on for that length of time when the headlamps
are turned off after the ignition is turned off,
or if the Auto mode is selected on vehicles with the
Auto Headlamps option. When Off is selected, the
headlamp delay feature is disabled.
² TRAIN REMOTE - When this feature is
selected the driver can choose to train up to four
remote keyless entry transmitters. The options
include Yes and No. The default is No. When Yes is
selected and the MENU button is pressed the EVIC
will display “PRESS REMOTE LOCK & UNLOCK
THEN PRESS UNLOCK”, followed by a chime to
indicate the training sequence can commence. You
have approximately 30 seconds to train up to four
transmitters, after each transmitter is trained a
chime will sound indicating that the training was
successful. If remote link to memory is “YES” , the
first transmitter trained will be associated with
memory setting 1 and the second transmitter trained
will be associated with memory setting 2. Additional
transmitters will not be associated with a memory
setting. When you have finished training the transmitters,
press the menu button again and the EVIC
will display “TRAIN DONE “X” TRAINED. If no
transmitters are trained within approx. 30 seconds
the EVIC will display “TRAIN TIMEOUT”.
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Remove overhead console. Refer to Overhead
Console Removal and Installation in this section(Refer
to 8 - ELECTRICAL/OVERHEAD CONSOLE -
REMOVAL).
(3) Remove the screws holding the EVIC module in
the overhead console.
(4) Remove EVIC module from console assembly.
INSTALLATION
(1) Position the EVIC module in the overhead console.
(2) Install the screws holding the EVIC module in
the overhead console.
(3) Install the overhead console (Refer to 8 -
ELECTRICAL/OVERHEAD CONSOLE - INSTALLATION).
(4) Connect the battery negative cable.
NOTE: If a new EVIC module has been installed, the
compass will have to be calibrated and the variance
set. Refer to Compass Variation Adjustment and
Compass Calibration in the Service Procedures section
of this group for the procedures.

 

Was it hot out and/or under the hood? Manual says the temp sensor is under the hood. If it was hot out and the engine was hot as well, the temp around the sensor might have gone above the range of the device. Then after a short drive the heat was purged and it worked again... just a guess.

 

I dont think his temp guage was the culprit here as he said all displays were --.

The ambient temp guage registers between -40F and +140F. I live in FL and most of the time I dont get a reading over 100F even after the truck has been sitting after driving it, but you are right that it will "cool" off as the air is moved around it when you start driving again.

 

I will try the diagnostics after I get off work and post back what I find. Thanks for the info!