I think my ECM is bad? Help!

[Allcagedup]

94 hardbody 2.4L manual

So I have searched the web and on here for days and can not find anything on what my truck is doing.

I turn on the ignition (engine not running) the red and green lights on the ECM blinks 9 times along with the fuel relay clicks 9 times and the check engine light comes on and the ECM goes into what must be fail safe mode. It will crank and run but idle is 1k and it over fuels bad and unplugging any sensor really doesn’t change anything..

Any ideas? I’m thinking the ECM is bad.

Oh and trying to pull engine codes doesn’t work. I can go through the engine diagnostics procedure with the dial on the ECM and it does nothing. No lights flash.

[dvdswan]

OBD I has a test mode. Run the test and see what code(s) come up.

[diosmuertos]

Here’s a good write up on using the other modes on the ecu

[Allcagedup]

Originally Posted by dvdswan

OBD I has a test mode. Run the test and see what code(s) come up.

All these test modes (like pulling engine codes) begins with turning the ignition switch on, turning the dial fully clockwise and waiting for the LEDs to flash a number of times then turning the dial, pressing the gas petal, etc, for whatever mode you want to test


My ECM does nothing when I put the key switch on and turn the dial fully clockwise. The red LED comes on and nothing else. No flashing from the red or green, the green does not even come on.

[Deerhurst]

Fusable links ok?

Your green LED may have died. You can do the LED relocation mod to get it back using the check connector.

[Allcagedup]

Originally Posted by Deerhurst

Fusable links ok?

Your green LED may have died. You can do the LED relocation mod to get it back using the check connector.

Fusible links are fine. The green light works fine. As mentioned in my first post when the ignition is turned to ON the green and red LED lights both blinks 9 times (while also the fuel pump relay clicks 9 times) then the ECM goes into a fault state and the ECM goes into what must be fail-safe mode. I can then crank the truck and it idles high and over fuels.

I can tell at some point the engine was pulled and rebuilt. I honestly believe somehow in that process something was shorted and fried the ECM because I can not find anyone or anywhere on the web that has experienced this.

[89'HBV6]

OK, so have you researched what local junkyards you have? If not, please do. That may be your best option, when it comes to finding a replacement ECU.

It will need to come from a 94'/2.4L/MT... most likely, no exceptions.

[jp2code]

Originally Posted by Allcagedup

All these test modes (like pulling engine codes) begins with turning the ignition switch on, turning the dial fully clockwise and waiting for the LEDs to flash a number of times then turning the dial, pressing the gas petal, etc, for whatever mode you want to test

My ECM does nothing when I put the key switch on and turn the dial fully clockwise. The red LED comes on and nothing else. No flashing from the red or green, the green does not even come on.

Usually, if the ECU is bad, the engine won't crank. So I'm inclined to rule that out.

In my signature below, I have a video where I recorded myself checking the codes on my 94. Watch it and report back if that's how you are checking your codes.

The clicking noise could be several things:

1) a faulty relay (happens often, just find a similar relay and swap it),
2) low battery voltage (check with a voltmeter),
3) corroded battery cables (voltage from negative battery post to bolt on the starter should be the same as the battery voltage), or
4) a bad ignition switch (I've replaced mine twice since 2010).

Start with the easy ones and work your way down.

[Allcagedup]

Well, I found it guys. Just as I thought the ECM was bad. After pulling it I found a bad trace on the circuit board and a bad 220uF capacitor.

Apparently, due to these failures, the truck was going into a fail-safe mode like an open-loop mode to keep from damaging the engine.

I hope this helps guys on here because I do believe this is a first for these trucks, as I have not found anything on the web regarding the symptoms I had.

I am repairing the ECM as we speak. It will be back in service this evening.

[Allcagedup]

Bad Trace on the circuit board