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