I found this information on HOW TO RUN INSTRUMENT PANEL ONBOARD DIAGNOSTIC TEST. Unfortunately, I cant find the code results chart (defining err results). guess I have to call the dealership. Hope this helps..
1.With the key in the ignition and in the off position press and hold the odometer / trip button.[br]
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2.Turn the truck to ‘On’ but do not start the truck.[br]
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3.After a few seconds the gauges will sweep from nothing to max, release the odometer / trip button.[br]
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4.The odometer should now read ‘GUAGE’, you are now in a information mode.[br]
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5.Start the truck[br]
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6.Now every time you press the odometer / trip button it will cycle through the information available.[br]
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7.When you shut the truck off the odometer will go back to showing mileage.[br]
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GAGE - Carries out gauge sweep of all gauges, then displays the present gauge values. Also carries out the check sum test on ROM and EEPROM.[br]
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All segments illuminated.[br]
Illuminates all odometer segments.[br]
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bulb[br]
Illuminates all micro-controlled lamps and LEDs.[br]
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r ####[br]
Returns to normal operation of all micro-controlled lamps and LEDs and displays hexadecimal value for ROM level (used when requesting assistance from the hotline).[br]
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nr####[br]
Displays hexidecimal ROM level and type as stored in non-volatile memory (NVM).[br]
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EE ##[br]
Displays hexadecimal value for EE level (used when requesting assistance from the hotline).[br]
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dt ####[br]
Displays hexadecimal code for the final manufacturing date.[br]
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###C[br]
Gas engines display last temperature gauge input value from SCP, temperature gauge will indicate present temperature. Diesel engine displays present temperature analog/digital input in decimal as a ratio, temperature gauge will indicate present temperature.[br]
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dtc ####[br]
Displays a 16 bit DTC in hexidecimal format. DTCs displayed are those detected in continuous operation not during self-test.[br]
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EnG[br]
Displays English speed value being input, speedometer will indicate present speed.[br]
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m[br]
Displays metric speed value being input, speedometer will indicate present speed.[br]
tAc Displays the tachometer value being input to the instrument cluster. Tachometer will indicate present rpm.[br]
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FUEL[br]
Displays the present analog/digital fuel level being input to the instrument cluster as a ratio.[br]
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OIL[br]
Displays the last analog/digital reading of the oil pressure switch contact resistance, oil gauge will indicate present level.[br]
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br[br]
Displays the brake fluid level in an analog/digital ratio value.[br]
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bAt ##.#[br]
Displays present battery analog/digital voltage.[br]
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rhEo[br]
Displays present hexadecimal pulse width modulation (PWM) dimming input.[br]
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rhi, rhS, rho[br]
Alternating 1 second display of pulse width modulation (PWM) input duty cycle, SCP hexidecimal dimming step, output driver counts in hexadecimal.[br]
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Cr[br]
RUN/START sense circuit check.[br]
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PA, Pb, PC, and Pd[br]
Displays 8-bit hexadecimal value for the Port A, B, C, and D readings (used when requesting information from the hotline).[br]
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PE0-PE7[br]
Displays 8-bit hexadecimal value for the Port E0-Port E7 in analog/digital readings