I just installed a new ECU in my car and I was out using the scan tool on it. I had the key turned to "on" but the engine was not running. I then cranked and started the engine. It was running pretty rough so I went to check the scan tool. I went to the sensor readings and pressed the "real time" button, nothing. I turned it off and then back on, pressed "Scan", nothing..."Vehicle not responding". Turned the car off and back on, pressed "Scan", nothing. Disconnected the battery, let it sit, reconnected, turned it on, pressed "Scan", nothing. I can't think of anything that would cause the scanner to just crap-out like this. I don't have another car to test it out on, so I can't be sure that it's not the scanner. Anyone got any ideas?

-Mark W.
'88 SC Camaro w/ 305 TBI

 

i'd guess the ecm isn't working, getting power, or not grounded.

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ICON Motorsports

1st & 3rd

 

You think? The car will run (abit rough) and the SES light isn't lit up. It's a brand-spanking-new ECU too. Oh yeah, it would scan until I started the car...that's when it crapped-out.
How could I check for bad ECU ground/power supply?

-Mark W.
'88 SC Camaro w/ 305 TBI

 

Check the connection at the ECM, make sure there arent any missing or bent pins.

 

I just experienced the same in my olds 442. I was getting crappy gas mileage and when the ECM was checked, it gave no information. It was as if there was no ECM at all. Needless to say, I ordered a new one.

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87 IROC 350 TPI with less than 10k original miles
www.users.uswest.net/~smoyer/iroc.htm

 

Just jiggle the connector to the aldl and make sure it's firmly on there. Mine does that intermittently but it's fine. If you can never get it to work, my guess would be you got a bum ecu or maybe a bum scanner.

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Base: 89 Iroc-Z LB9 auto 2.73 posi
Exh: 3" Dynomax muffler, 3" Pipe in place of cat
Ign: Accel 300+ wires, cap&rotor
Fuel: Cleaned and flow-matched injectors, afpr, !air pump&diverter valve
Sound: Clarion deck, Kicker speakers and amps
Suspension: KYB Shocks, BMR Strut Tower Brace
Misc: TB Bypass, Synthetic Oil, Flexlite Transmission cooler,
free mods, hopefully engine swap and 4th gen seats in the works...

 

Well, this is kinda strange. I took a handfull of PROMs all burned with the same image down to the driveway, disconnected the battery, check the wires going into the ECU connectors (they all seem pretty tight, but on the back of the little connector there's a yellow "tab" and it's not there on the big one), plugged in a PROM, reconnected the battery, scanned, when it failed swapped PROMs, after about 3 it did scan. It ran just like it did when it didn't scan (which makes me think that it's the scanner). I was flipping through the sensor readings and realized that I'd forgotten to plug in the IAT sensor. I jumped out of the car and plugged it in. When I got back in the car and looked at the scanner it was reading right...for about 3 seconds and then it quit reading real time, and wouldn't scan again. Bizzare. Oh yeah, the reason I burned the PROMs is I don't have a stock chip anymore. I'd been trying to swap to a 7747 ECU and burn my own custom chips, but never got the swap working correctly. I've gone back to the stock ECU and I'm just gonna fork out the cash for a custom chip from some company.

-Mark W.
'88 SC Camaro w/ 305 TBI

 

That seems like further evidence that it's just an intermittent problem at the aldl/scanner connection. When I plug in my autoXray, almost every time it says "car not responding" but I just jiggle and press on the plug and scan again - it always works eventually. Good luck.