General Motors Honors McKaig Chevrolet Pontiac Buick PDF

The ability to view engine-operating data, such as oil pressure and coolant temperature, in digital form on the instrument panel has been a feature of Corvettes since 1984. Starting in model year 1992 (MY92), the C4 IP would even display limited diagnostic data relating to the car’s on-board computer systems. C5′s capacity to do that is significantly expanded. The new car has 11 computer “modules” that transmit diagnostics: Powertrain Control Module (PCM),Traction Control System (TCS, which combines traction control, ABS and, on cars built after 12/15/97, the optional Active Handling System), Real Time Damping (RTD), Body Control Module (BCM), Instrument Panel Cluster (IPC), radio, heating-ventilation-air conditioning (HVAC), Left Door Control Module (LDCM), Right Door Control Module (RDCM), Seat Control Module (SCM) and Remote Function Actuation (RFA). The IPC display, the 20-character, vacuum-fluorescent screen above the steering column that says “Corvette by Chevrolet” every time you start the car, is a powerful device.

Its primary function is to display warning and status messages from the modules. For cars built before 12/15/97, there are 48 of these warning/status messages. A few additional messages come from cars built after that date and equipped with the Active Handling option. A list of the warning/status messages can be found in your Owner’s Manual or in the Service Manual for your model year. The IPC can display powertrain operating information and tire pressures by simply pressing different buttons on the Driver Information Center (DIC) to the right of the instrument panel. In addition, using the “options” button, you can configure the C5′s keyless entry and security systems. Use of the IPC and DIC for these purposes is discussed in your

Owner’s Manual DIY Service Techs will be most interested in the IPC’s display of diagnostic trouble codes (DTC) for all modules that transmit them. The “diagnostic display” mode is entered with the following procedure: 1) turn on the ignition but don’t start the engine. 2) press the “reset” button to turn off any warning messages 2) press and hold “options” and 4) while holding “options”, press “fuel” four times within a 10-second period. Initially, on-board diagnostics go into “automatic” mode which shows DTCs in a pre-set sequence: PCM-TCS-RTD-BCM-IPC-radio-HVAC-LDCM-RDCM-SCM-RFA. 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 a malfunction is present in the system whose module is displaying data. A history code indicates a problem existed some-time in the last 40 or 50 ignition cycles. When not accompanied by a current code of the same number, it’s possible evidence of a previous problem, now solved, that was not removed by clearing codes. More likely it indicates an intermittent malfunction.

“Intermittents” are the most challenging DTCs. An intermittent may have happened 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 display-ing 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 modules, the system goes into the manual mode which allows selection of each module using combinations of DIC buttons. Manual mode can also be entered during the automatic sequence by pressing any button except “E/M”. Once the IPC displays “manual diagnostics,” select a 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 go 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. Once you have DTCs, the next question is: What to do with the information?

First, consult the factory service manual. Any serious C5 DIY should invest in the Corvette Service Manual of the appropriate model year. Unfortunately, it is an expensive set of three books totaling (1997 edition) 3890 pages and stacking 4 1/4 inches high. In spite of its cost and size, the Service Manual is a requirement if you want to understand and work on your C5. They are available through Chevrolet dealers and mail order sources, such as Ecklers and Mid America.

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