OBD2 no communication

PAUL ALLRED

MEMBER
1996 CHEVROLET 1500
5.7L
V8
4WD
MANUAL
200,000 MILES

Check engine light is on. Obd 2 reads only error. Have tried 3 different scanners all say the same thing. Truck backfires like popcorn under load. If I downshift to raise rpm's power gains, popcorn stops. Idles almost perfect. No popping at all. Has new fuel pump 55-65 psi (fires and runs on a bump of the switch) and inline fuel filter, new spark plugs. Did remove cats due to they were stopped up. If I could just get the obd 2 to work I could figure out the rest. No blown fuses, power is on the #16 pin. I heard MAF sensor could cause a no read. Replaced multi function switch, I put in one without cruise control verses with cruise. Money was tight, would this have any affect on situation?

1 Reply

ASEMASTER6371

MECHANIC
52,797 POSTS

Good morning,

From your description, it is a mechanical issue, not an electronic issue.

https://www.2carpros.com/articles/engine-backfires-while-running

A common issue for this back in the day was a worn camshaft lobes. When the lobes wear down and the valves do not move the correct amount, it will backfire as you have described.

https://www.2carpros.com/articles/how-camshaft-variable-valve-timing-works

I would remove the valve covers and watch the action of the rocker arms at idle. I think you are going to find some of the rocker arms are barely moving.

As far as the communication, it could be the PCM itself. Try removing the connectors at the PCM and cleaning the pins and reinstalling them. Then check and see if it will communicate.

Roy

OBD2 no communication

1 Reply

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