IPC Codes

The IPC display, the
20-character, vacuum florescent screen above the steering column that
says “Corvette by Chevrolet” every time you turn on the key is a powerful
device.

DIY Service Techs
are going to be most
interested in the LPG�s ability to show diagnostic
trouble
codes (DTC) for all the modules that transmit them..

The “diagnostic
display”
mode is entered with the following Procedure: Page
8-500

1. Turn on the ignition
   but don’t start
   the engine.
2. Press the “reset”
   button to turn off
   any warning messages
3. Press and hold
   “options”
   and
4. While holding “options”,
   press “fuel” four times
   within a 10-Second period.

Initially, the on-board
diagnostics go into the “automatic” mode, which shows each module’s DTCs
in a pre-set sequence: (Page No. are for the GM Service
Manual)

• 10 PCNI Powertrain
  Control
  Module page 6-357 – 6-361
• 28 TCS Traction
  Control
  system ABS on page 5-86
• ?? RTD Real Time
  damping
  page 3-136
• 40 BCM Body Control
  Module page 8-405
  LTD Page 8-727
• 60 [PC instrument
  Pane! Cluster page
  8-508
• 80 radio page 8-213
  
• 99 FIVAC Heater
  Vent-Air Conditioning page 1-118
• A0 LDCM Left Door
  Control module page 8-904 to 8-951
• Al RDCM Right Door
  Control Module page 8-904 to 8-951
• AC SCM Seat Control
  module page 8-1064-8-1082
• B0 RFA Remote Function
  Actuation page 8-676

For each module, all
DTCs will be displayed. If none are present in a module, you will see
“no more codes” on the ICP display. There are two kinds of DTCs, “Current”
and “History,” designated with a letter suffix, “C” or “H”. A
current
code indicates that the malfunction is present in the
system whose module
is displaying data. A history code
indicates a problem existed in that
module sometime in the
last 40 or 50 ignition cycles. When not accompanied
by a
current code of the same number, it is possible it’s evidence of
a previous problem. Now solved, that was not removed by clearing codes.
More likely is that a history code indicates an intermittent
malfunction.

“Intermittent” are
the most
challenging DTCs. An intermittent may have happened only once,
may have happened more than once but is inconsistent in its appearance
or may be happening on a regular basis but not at the time the
IPC is
displaying codes. History codes can also be caused by a
current malfunction
in a system that is not Operating at the
time DTCs are displayed. An example
is the rear window
defogger, which doesn’t operate until the BCM detects
engine
rpm. For history codes set by a system that does not operate with
the key on and engine off, a special diagnostic tool called a “scan tester
is necessary to properly diagnose the
malfunction.

Once the IPC has displayed
all 11
modules, the system goes into the manual mode, which allows selection
of each module, using combinations of DIC buttons. The manual mode can
also be entered at any time during the automatic sequence by
pressing
any button except “E/M”. Once the IPC displays
“manual diagnostics”, you
may select a particular module by
pressing the options button to go forward
or the “trip” button
to go back. Once a system is selected and a DTC is
displayed,
if more than one are present; press “gages” To move forward
or
“fuel” to go back. To exit the diagnostic mode at any time, press E/M”.
If you want to erase or “clear” codes, press “reset”. Clearing
a code
does not repair a problem. You are simply erasing the
evidence of it in
the module’s memory.

Click
here to download the Word
document of IPC display codes