Questions and Answers

GM Digital EGR Testing Q. Hello Vincent, My question concerns a 1994 Chevrolet Beretta. It has a 3100 SFI V-6, automatic transmission, A/C, and digital EGR. The check engine light illuminated almost every time I drive it at a certain time. That is when the engine is warm and at 55-65 mph at a deceleration.

I had a local shop pull the trouble codes to see what they were. Codes 75, 76, and 77 all came up and a test drive under those conditions mentioned earlier produced the same results.

So, these codes are EGR Solenoid #1, #2, and #3 errors. I did a resistance check on the solenoid and I was wondering what are the specifications if there are any? I can tell you that both solenoid 1 & 2 tested roughly 22 ohms. Solenoid #3, however, tested roughly 12 ohms of resistance. I at least know that the EGR hasn't shorted but that 12 ohm measurement has me concerned about the integrity of this valve. Do you know if these sound like reasonable values?

Now that I've tested the resistance, though, what would be the next step in diagnosing this EGR failure? I was thinking of testing to see if the ignition is sending power to the EGR and maybe a voltage drop test at each solenoid. Like I say, I'm not too sure of what to do and where to go with this or if I need any special tools like a scan tool. I'm just a beginning technician with very little electrical experience in engine controls and emissions controls. Any help or ideas in testing this circuit will be of great help to me.

Thanks!

A. If you had a "Tech 1" which is what they use in GM dealerships on OBD-I cars, you could scan codes, check data, and command the EGR solenoids open and closed. My guess is that the valve is bad but you need to check for voltage to the valve first. I'm not sure on the resistance readings, I don't even know if that is a valid test for this valve. Check for 12 volts at the pink wire. If okay I would get it scanned so you know what's up.

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