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165 ECM testing

Old Nov 22, 2006 | 08:10 PM
  #1  
cwalsh's Avatar
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From: O Fallon, MO
Car: 2004 Corvette
Engine: LS1
Transmission: T56
165 ECM testing

I am looking for some one who can test an ECM out of the car. When painting the car last year I had the dash out & like an idiot did not realize water dripped into the connectors. I found that this year after having a rich condition & just unplugged the ECM tonight to find corrosion on terminal pins A1-A6 & B1-B6. I am pretty sure something had to fry but would like to have it tested before plopping down money.

Chris
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Old Nov 23, 2006 | 09:13 AM
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From: Browns Town
Car: 86 Monte SS (730,$8D,G3,AP,4K,S_V4)
Engine: 406 Hyd Roller 236/242
Transmission: 700R4 HomeBrew, 2.4K stall
Axle/Gears: 3:73 Posi, 7.5 Soon to break
Should be able to test this out for the most part on the car.
Clean out the terminals as best as you can and then try it.

A1 is fuel pump relay output (going out to turn on the relay 12+output)
A6 is switched ignition power to the ECM
The rest on the "A" terminals are solenoids that are powered at the solenoids and grounded through the ECM.
The exception is "A5" SES light that may ground or be powered (not sure)
If there was cross connection between a powered wire and the solenoid connection pins that ground through the ECM, you could have burned an output up on one or all of them by not having any coil resistance to limit the current flow. They can only tolerate something like 400 mA each.
A2 = AIR valve sol switched to port
A3 = Cannister purge sol
A4 = EGR sol
A5 = SES light
There is a mode that cycles through the solenoids but I'm not sure at the moment of how to make that happen. Could be a certain resistance applied across the ALDL connector with just the key on.

The pins on the "B" header are more of a question of problems if it won't run at all.
B1 = 12 volts constant power
B2 = fuel pump signal (input to ECM)
B3 = EST dist ref low
B4 = not used (on my list anyway)
B5 = EST dist ref high
B6 = not used (on my list anyway)
These would play havoc on your ignition and probably wouldn't run.
I'm thinking you are ok there because it runs and you havn't blown fuses.

Putting a test light on the ECM side of the solenoids should indicate when the ECM is grounding the solenoid to operate (light will go off when solenoid is turned on)
there will be power on both sides of the solenoid until the ECM grounds it to make it work so if using voltage measurements you'll know why.
HTH
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Old Nov 25, 2006 | 06:26 AM
  #3  
cwalsh's Avatar
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From: O Fallon, MO
Car: 2004 Corvette
Engine: LS1
Transmission: T56
I got that same info from my service manual. Thanks. The car does run but very poorly. I can see where water basically filled the entire plug. Who knows how full it ws when I next ran it again. I am going to swap it out with a friends and look at it on a scanner to make sure everything is really OK.

Chris
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