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International Automotive Technicians Network
LY7 and LP1 ECMs, GM 3.6 HFV6
Posted to Technical Tips Forum on 1/30/2016 27 Replies

I don't know how long this tip will be applicable but starting late last year, I noticed it most starting in November, there have been a much higher rate of failed new ECMs for the early HFV6 cars, LY7 and LP1 engine RPOs. The service part number is 19260507 for the ECM in OE.

The typical failure of these ECMs leaves the key stuck in the ignition, the fuel and coolant temp gauges stuck all the way to the left and the security and traction control warning lights on. When you install a new ECM before programming it if it is a good ECM the key should begin releasing, the fuel and coolant temp gauges should begin working, and the traction warning light should extinguish.

If you are certain of your diagnosis, which is easily accomplished by looking for all the class 2 modules except ECM to be present on the class 2 message monitor and by looking for an active class 2 line at the ECM with a scope as well as power, grounds, and main relay activity, and your new ECM will not program and does not extinguish the traction light, restore the fuel and coolant temp gauges, or allow the key to be removed your new ECM is defective.

I have seen reports and fielded calls and emails where the shop asking for help has had to install as many as 5 new ECMs in order to have one that successfully programs. This tip is about that as well as how to identify an ECM that has no chance of successful programming before wasting your time or second guessing your diagnosis or equipment. I use an MDI and my laptop is up to the specs and beyond. And I have experienced at least one bad "new" ECM.

Good reman ECMs will allow key removal, restore fuel and coolant temp gauges, and will not light the traction warning light. If your replacement ECM fails to do all these things. Don't bother attempting to program. Just get another one (or two or three) and try until you get a good one.

Russell from Florida

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