E67 ECM short to ground??

[djrosa200]

All,

I have a perplexing problem. I have a 69 Camaro with an LS3 swap using a GMPP E67 ECM (p/n 19354331). The car runs great but when I was changing the battery I touched the ground post to the body and it sparked. I put a multimeter on it and measure 12 volts between the chassis and the negative terminal. Resistance measurements are in the range of megaohms. After much tracing, I have narrowed it down to the ?ECM keep alive? circuit that is feeding pin 20 in the blue connector. From the information I have, pin 20 should have positive 12 volts, so I believe all is wired correctly. If I pull the 10amp ?keep alive? fuse or disconnect the blue ECM connector, the short goes away. It?s not enough of a short to blow the 10amp fuse, so it does feel related to a semiconductor versus a typical short.

My question is whether or not an ECM can fail this way or if there might be a setting that I can change? My next step is to get a new ECM but wanted to see if there might be any other thoughts?.

Thanks in advance,
Dave

[gtstorey]

The ECM will always pull tiny bit of current and the if no other path to ground you will see the voltage across a voltmeter. This is why you need to have a trickle charger or disconnect the battery when its sits more than a couple of weeks.

[Alvin]

This just sounds like the body isn't well grounded. The body should have a ground to the battery and the engine should have the same.

It should have less than a couple ohms resistance checking between any two.

[gtstorey]

This just sounds like the body isn't well grounded. The body should have a ground to the battery and the engine should have the same.

It should have less than a couple ohms resistance checking between any two.

I think he is talking about with the negative battery terminal disconnected, so nothing is grounded except through whatever "other" connection he is making.

[abc]

Do a parasitic load test. EFI cars do have more parasitic load than non-EFI cars and each manufacture will have a max spec for it. I have several Gen 3 combos. but have never checked their actual parasitic load. I do now the experience you described is fairly normal so far. The best way to know for sure is find out exactly how much amperage it's drawing. Have you noticed any issues with it sitting for 4 weeks or less and the battery being depleted enough it will not crank the engine?

[djrosa200]

All,

Thank you for the replies. They were definitely helpful. Turns out that it is the standard parasitic load. After getting a new fuse for my meter, I'm measuring between 7mA and 8mA at steady state. What threw me in the beginning was the initial spark between my wrench on the ground terminal and the battery hold down - it was enough to cause a black spot on the wrench. I have a battery disconnect and every time I reconnect it, the Detroit Speed headlight door motors cycle - I believe that is what caused a higher current draw and led to the original issue. I left the battery disconnect in the connected position, attached the amp meter and then disconnected so it wouldn't cycle the headlight doors. ~7mA, so I'm happy! Thank you again.

Dave