Ecm is not sending a signal to trigger iac

**joegreen** · 12-18-2014

Hello, I have had a large vacuum leak from the throttle body for a while but since i only drive my truck every month or so i haven't messed with it. Today i went to check it out and it turns out the 1227747 ecm is not sending a signal to control the iac. What could be the problem?

Also I cannot for the life of me get my laptop to connect to the ecm. I did the timing patch and ever since then it just says connecting never connected. I have an older ftdi driver from 2009 that i know works. The aldl cable i built used to work fine. The tx/rx lights do not light up when i am trying to connect.

**Six_Shooter** · 12-18-2014

It sounds like you might be in limp home mode. Load a non patched bin and post the results.

**joegreen** · 12-18-2014

i will try that tomorrow

**joegreen** · 12-18-2014

ok so i put the afcb bin on the chip. So today when trying to get the iac to move i realized that the ground wire (pin a of the aldl port) was not connected to ground. I fixed this but i still get no movement from the iac.

**Six_Shooter** · 12-19-2014

Can you get data now?

**joegreen** · 12-19-2014

actually i never checked. I will check that tonight and get back with the results.

**joegreen** · 12-19-2014

ok, so i am currently checking to see if it connects and nothing. It just says connecting. I can test the cable and it says found and functional.

**JeepsAndGuns** · 12-19-2014

Does your check engine light work? If it does, what does it do when you turn on the key? Blink twice then stay on, or blink really fast?

**joegreen** · 12-19-2014

Actually i was never able to get my check engine light to work. I know its simple to hook up but the ecm would not light up the bulb. I tried troubleshooting that for days. I ended up just plugging into the ecm periodically.

**Six_Shooter** · 12-20-2014

There's a couple red flags popping up then...

If the CEL output is indeed non functional and the IAC outouts are also non-op, then it could be a quad driver issue.

When you tried connecting the CEL, you did have 12V to the other side of the bulb, correct?

**joegreen** · 12-20-2014

Yes i did have 12 volts on the other side of the bulb and the ecm is just there to ground out the light. I tried hooking up my volt meter in between the positive and the ecm ground and would get the dvom to display the 12 volts but i could not light up the light. I made sure i had the right bulb and what not. I did a bunch of tests but could not get the cel to illuminate but the ecm was sending out a ground signal to ground the bulb so at least i think the ecm is working correctly. I bought this tbi system off of craigslist and took it off of the doner vehicle myself. The guy also had a relatively new remanufactured ecm that he gave to me.

**joegreen** · 12-22-2014

Hello, just spent the last couple days replacing the upper ball joints/ control arm and lower ball joints on a ford ranger. Anyway any ideas on what to test regarding not being able to connect to the ecm and the ecm not sendibg a signal to the iac? Thanks for everyones input so far.

**fastacton** · 12-23-2014

It's sounding like you might have a bad ECM. Can you get hold of another one for testing?

**joegreen** · 12-23-2014

I dont know where to get another one. Could this ecm be bad even though its remanufactured and the truck runs.

**JeepsAndGuns** · 12-24-2014

Limp home mode will let the engine start and run, but not very good.
From what I remember back when I was running that ecm and accidently got in limp home mode, the IAC just pegged wide open and I was unable to connect to the ecm.

I would go through and check all the basics. Power, grounds, bad/broken connections. And yes, even if a part is new/reman, doesnt mean its good. I have had bad parts straight out of the box from a parts store.