pin 34 and 35 dead

[pete simon]

Hello
I am running MS2, V 3 board.2.905 code.
my problem is no output on pins 34 and 35, injector control.
pins 32 and 33 work normally.
new install, board passed all assembly checks. m/s has been controlling spark in this car for 6 months, EDIS4 setup.
when setting car up for fueling, could only get half my injectors to fire. found wire broken off at pin 34 and 35. restored connection, but still no injector firing.
car is now running fine with all 4 injectors on one circuit (pin 32/33)
Question is what did I damage on the board? Did I damage Q13? or can i run some tests on the board? both pins 34 and 35 show 3k ohms to ground.
the functioning pins show meghoms to ground.
Any insight would be appreciated. Pete

[DonTZ125]

R35 will be easier to lift one leg for testing without destroying anything. If your resistance goes back up, then yes, it's probably Q13. If not, carry on lifting pins until you find a dead component - I'd suggest D20, then D7.

Are you running lo-z injectors with PWM? If not, and lifting R35 cures the problem, I'd just finish pulling R35 and call it done.

[pete simon]

i am running hi impedance injectors, so no pwm.
if i lift a leg of r35 wont that disable that output if i leave it that way?
will try tonite and reply. thank you, pete

[DonTZ125]

Q12/13 and R34/35/36 comprise the PWM flyback damping circuit, and don't actually control the opening and closing of the injector(s). They protect the FET (that DOES open and close the injectors) from the voltage spikes brought on by high(er)-frequency on/off of PWM.

[Matt Cramer]

I've got a guide to troubleshooting the outputs here:

http://www.DIYAutoTune.com/tech_article ... ooting.htm

[pete simon]

thank you for the link.
it explains the circuit perfectly. it should be all i need.
Thank you, Pete