2G Voltage in ECMLink different than alt and batt?

[HaveBlue83]

I have this exact problem in my 99 GST......I have 13.8v at the alt and battery. The ECU shows 13.4v.

After 10-20min driving it goes to 12.8v-13.1v, wot is 12.8v and the dash lights for brake and oil come on of when doing a pull sometimes. With headlights on it's also a draw especially at idle, and I've seen down to 12.3 with headlights on, at night, at a stop light.

I've already checked grounds, and the batt and alt seem fine. Maybe .4v lower at warmed up than cold. I ordered a new 90A alt just in case. I also added a ground wire from alt ground post to the frame rail.

I don't see a batt to alt issue. I'm seeing a drop on the logs and via my volts gauge. Soooo it now seems this 95 EPROM is going to go to Tom next.

 

[motomattx]

I have this exact problem in my 99 GST......I have 13.8v at the alt and battery. The ECU shows 13.4v.

After 10-20min driving it goes to 12.8v-13.1v, wot is 12.8v and the dash lights for brake and oil come on of when doing a pull sometimes. With headlights on it's also a draw especially at idle, and I've seen down to 12.3 with headlights on, at night, at a stop light.

I've already checked grounds, and the batt and alt seem fine. Maybe .4v lower at warmed up than cold. I ordered a new 90A alt just in case. I also added a ground wire from alt ground post to the frame rail.

I don't see a batt to alt issue. I'm seeing a drop on the logs and via my volts gauge. Soooo it now seems this 95 EPROM is going to go to Tom next.

Yours sound more like an alternator issue, if its a cheapo parts store reman unit, no matter who its from consider it suspect and probably junk, they will act up intermittently and the parts store tests wont show it as bad even though it is.

 

[HaveBlue83]

Yours sound more like an alternator issue, if its a cheapo parts store reman unit, no matter who its from consider it suspect and probably junk, they will act up intermittently and the parts store tests wont show it as bad even though it is.

I have a new WEI 90A I just got in in prep for swapping it out. The car only has 58k on it and most all the parts are original on it. I will pull the ECU and check, but I'm thinking I'm going to find a bad board. If I don't, and the spare eprom I have gets socketed and tried out, and it's still happening, I will swap the alt. I have done all alt prolly 5+ times on these cars. I went to the 90A Saturn units on my mirage swap and I get a few years from them before they fry out .

I'm also getting some weird things.....AC fan turning on low when the car is cold, and the front O2 refuses to cycle since I got the car last month. And I put a new sensor in. So there is enough to tell me to check the ECU out.

 

[chrisman287]

I have a new WEI 90A I just got in in prep for swapping it out.

Hope you have better luck than I did. Mine was crap out the box. Voltage was good on my gauge but dummy lights stayed lit. Ended up putting a used OEM unit in.

 

[HaveBlue83]

Hope you have better luck than I did. Mine was crap out the box. Voltage was good on my gauge but dummy lights stayed lit. Ended up putting a used OEM unit in.

If it's crap, I'll return it to rock auto. I didn't get an ac Delco unit because the pictured plug was a 2 prong not a 4, so we shall see. It's the original alt in there afaik, I think it's just the ECU. I have a spare eprom that's going out tomorrow to get checked, caps, and socketed so next week ish I'll have that back and I can swap it out.

My dummy lights randomly come on, only faintly, when doing pulls and punching it. But when u read the alt and batt, it's FINE. so I say it's caps.