Is there a trick to read the code by counting the flashes on a 94 GMC
4.3 vortec. I was out again last weekend and again the engine light comes on when I am towing my camper.....I got 306 km's out of that tank Brutal. Other than the CPI leaking and the o2 sensor that I have allready replaced what is the most common sensor to fail on these units?
If it has a 14 pin ALDL and cavities "A" and "B" are occupied, you can jumper those two and count check engine light flashes.
GMC Jimmy - YES - The 94 was the last year for the old square body design and was still OBDI Look under the dash around the steering column. Find the 12 pin DLC connector. Using a paper clip, small piece of wire or a commercially available "code reader", ground terminal "A" to "B". There should only be five (5) terminals in this connector, four along the top and one on the bottom. Above the one on the bottom (M), is terminal A and B.
After grounding A to B, turn ignition key ON, do not start engine. The MIL will start to flash. One flash, short pause, two flashes, long pause, subsequent flashes. This is code 12 indicating the computer diagnostics is working. It will repeat two more times for a total of three code 12 flashes, then any stored trouble codes will display, repeating each 3 times. Code 12 will flash again when all codes have been displayed. Once you have the code either post it here OR go to
GMC S/T - MAYBE - This was the year of changeover to the new body style. That vehicle could be OBD I, OR OBD II depending on build date.
GMC Full sized - Yes - These were OBDI until 95
Count the pins on the ALDL connector
12 pins = OBDI 16 pins = OBDI.5 or II OR look on the vehicle emissions label under the hood. It will tell you.Most common failures - CPI, Fuel pressure regulator, Fuel lines (Nut Kit), EGR (gets blocked open by carbon), Intake gasket leaking into engine on the ends of the manifold.
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