How-to: Jeep XJ Cherokee Erratic Gauges and "No
readout at left is our 1999 XJ Cherokee with the engine running! This not so rare "No Bus"
signal and gauge "drop-off" occurs, unexpectedly, on several Jeep models, including XJ Cherokees and TJ
Wranglers from the OBD-II era. According to Chrysler's TSB #08-15-99, the cause on the XJ Cherokee,
TJ Wrangler and other models is a defective wire plug. At right is the Chrysler/Jeep
recommended cure, Mopar replacement plug and wires
time the tach and speedometer dropped to "0" and the Air Bag light came on, we held our breath and waited for
the bags to deploy, which the fortunately did not. Would the engine stall? Were we about to watch smoke
pour out from the dashboard? Were the instruments fried?
It was a hot summer day at the high
desert, the Jeep had parked in the driveway for awhile. The dashboard around the instrument panel was
hot, and this would later serve as a clue. When the gauges suddenly jumped back to a normal reading, the
cabin had cooled considerably, and the problem did not reoccur until the next time the vehicle heat soaked in
the driveway. Catching the "No Bus" signal in the carport that evening launched a search
of Chrysler's service literature for a possible cause.
widespread issue cropped up in the late '90s, Chrysler issued the Jeep TSB 08-15-99. (There was an earlier TSB,
this bulletin superseded the earlier release.) Chrysler believed the issue was corroded pins on
the instrument cluster wiring plugs. Click here for a PDF
of the official Chrysler bulletin and repair instructions. Read the instruction portion for
details and cautions.
The installation of the new plug and
wires involves removal of the instrument panel, which is covered in a Jeep factory workshop manual. Here is a
summary of the task to help illustrate the repair involved. Accessing the instrument panel is basic.
Changing out the plug receptacle and wires does require soldering
Note: Some owners have
success simply unplugging the instrument panel and reinstalling it. This might remove corrosion or at least give
the contacts a new lease. Claims by some are that this procedure has worked for several years
and is still working. Our Cherokee did not manifest a "No Bus" or tachometer, speedometer and
gauge drop-off until 130K miles of service. You might try the unplug, clean the contacts as described in
the TSB, and reinstall the panel without doing the plug change. If that doesn't do it, there's the TSB
Begin with disconnecting the negative battery
cable! Accidentally deploying the air bags or frying electrical wires must be
avoided. (Cautions about working near the air bags can be found in the
Jeep factory service manual.) At left, the negative battery cable is safely away from the post. At
right, the driver's side kick panel and shield plate below the steering column get removed for
access to the instrument panel bezel.
The center panel comes off by carefully unsnapping
the clips. The instrument panel bezel requires screw removal and unclipping. This is a 1999 Jeep XJ
Cherokee, likely one of the most practical and simple 4x4 vehicles built since the Jeep CJ
The dash panel cover also snaps into place. Unclip the front
(furthest from windshield) first. At the angle you see, the panel pulls outward from the windshield end.
Clips make this removal and installation simple. At right is the Mopar #05016261AA new plug with wires.
(Heftier heat shrink tubes are an add-on for wire reinforcement and additional insulation.) Pay
close attention to the color code labels. Wire colors are not all matched. The labels
indicate where each wire attaches to the factory plug's wires.
Instrument panel removed, cut the wires near the old plug.
Here, heat shrink tubing gets installed before wires are spliced. At left, the first wires get matched, the
two ends get an overlap-and-twist splice. At right, the rosin core solder has made a neat bond of
the two wires. The heat shrink tubing is kept away from the heat at this
an ideal situation, these wires would be cut on 1/2" staggers to keep splices apart and reduce the
risk of insulation failure causing shorts between wires. However, this spur of the OEM harness
has only a few inches of length, which does not lend itself to staggering ten wires! Instead,
attention is spent on insulating the wires at the splice with both heat shrink tubing and electrical tape
prior to taping the entire section of harness. In the TSB, Chrysler recommends a 1/2" stagger between
each wire splice. Normally, that would be standard procedure for multi-wire
At left is a classic overlap/twist splice of two wires. The
aim is to maximize the wire contact to assure adequate amperage flow from one wire to the next. At
the same time, the wires have a minimal increase in diameter for bundling within the taped harness. The
fully soldered joint at right has rosin core solder thoroughly saturating the wires—without overheating
adjacent sections. Note that heat shrink tube is unaffected.
There are 10 wires on this plug replacement. By splitting the
solder chores into two gangs of 5 wires apiece (each row of the plug), the separation makes soldering easier.
Always keep adjacent wires away from the soldering tip's heat. Avoid touching a soldering tip to the
insulation of other wires! A tiny screwdriver or pick can be carefully used to stretch a slightly
shrunken end of the heat shrink tubing prior to sliding the tubing into
At left, 5 of the wires have heat shrink tubing in place and
shaped. Each tube was heated with a wooden kitchen match passed carefully along the heat shrink
tube—without damaging the tube or any adjacent wiring insulation.
The soldering device is a simple 30W gun, inexpensive and
available from sources like Radio Shack. The solder is 60/40 with rosin core. (Always use rosin core, never
acid core, protect yourself from the lead fumes!) One way to shrink the heat shrink tubing is
the wooden match technique. Torches for this task are available but work no better than matches.
With practice, you can quickly apply heat to the tubing and shrink it without melting or
distorting the tubing or nearby wire insulation.
All of the wires are now spliced. As much time was spent
carefully identifying the labeled colors as it took to solder the wires. As added insulation, without
the space to stagger the wire splices, each heat shrink tube section gets wrapped individually with
electrical tape. The finished wire splices have 1) heat shrink tubing, 2) electrical tape wrap of each heat
shrink tube plus 3) the final harness is double-wrapped with electrical tape to resemble
a factory wiring section. Quality electrical tape is UL rated at 600V. The look is OEM, the repair uses
OEM Mopar parts, and the final results follow the 08-15-99 Jeep TSB for the "No Bus"
and erratic gauges/instruments issue.
Both plugs back in place, this is the alignment for the plugs
and instrument panel. At right, Permatex Dielectric Grease* provides added protection against the alleged
source for the "No Bus": corrosion on the plug pins. This vehicle was based at Nevada's high
desert country from day one, so unless there is condensation from defroster or other sources, there
is no reason to suspect that corrosion occurred. There was none of the black or gray coating on the
pins. We assumed that the plug connector was defective.
Note: There is
apparently controversy about the use of dielectric grease. In my experience, this grease applied at plug
connectors has helped prevent exactly what Chrysler claims will happen to the pin-to-clip connections at this
panel plug, i.e., corrosion over time. A small dab at each of these plug openings will prevent
the corrosion claimed to create the problem here. For those still in doubt about dialectric grease, here is a
third party YouTube video on dielectric
grease. The Permatex official website
also has information on
the Permatex® Dielectric Tune-Up Grease used on this
project. Judge for yourself.
The well insulated new wire and
plug harness looks "factory". Make sure that any extra harness length fits safely beneath the panel cover.
This fix looks right and should readily outlast the original plug and wiring! The instrument
panel must be aligned carefully with these plugs as you fit the panel into place. Do not bend prongs
on the instrument panel sockets! Four screws retain the panel once the plugs insert fully. At
right, the dash cover and instrument panel bezel fit back in place. The balance of parts reinstall in the reverse
order of the disassembly. Make sure everything is in place and fitted properly before reattaching the negative