what are the signs of a bad ECU unit

what is the signs of a bad ecu unit on a 99 tacma and does the ecu power the coil packs?

 

Does the CEL come on with key ON, engine off?

What engine?
2.4, 2.7, or 3.4?

 

it’s 6 cyl what is the cel

 

Check engine light. What trouble are you having?

 

With the key ON, the Black/Red wire should have power at the ignition coils.

 

Someone let the smoke out of it.

 

In simple terms, signs of a bad ECM is that you've checked everything and it's good. You've scratched your head and checked everything again then ask for second opinion because you don't believe it's the ECM.

3 easy steps for electrical diag

1.)Check the component ( if possible)
2.)Check the circuit output
3.)Check the wiring integrity by disconnecting the circuit and applying battery power to one end and a incandescent test light at the least on the other end and look for full brilliance of the light

if your problem is not found in those 3 steps and you've checked everything properly, chances are the issue is with the part the can't check. In this case the ECM

 

before the engine died i heard chirping sounds from the ecu area after that could not get it started shot starter fluid into intake ran 8 minutes than died

 

Check for codes first, trust me. I've bit myself in the ass many times by not taking advantage of the on board diagnostics system in vehicles.

Alot of things can cause that.

Not saying it can't be the ECM as on my 92 Camry that I bought a little while ago not running was in fact caused by an Igniter AND ECM failure but as a former dealer tech, check for codes before assuming it's the ECM

 

This^^^^ X2

 

Does your truck have a tach?
If so, see if the tach moves when cranking.

I just went through something similar on a Ford w/460 engine.
Intermittent engine stalling, that eventually lead to a no start.
It was the pickup coil/sensor that send an RPM signal to the ICM/ECM.

BUT…..Start with a code scan first.

 

I’m not able to pull diagrams right now.
@Dm93 can if he is around.

I think it is an AM fuse. But I don’t really remember.

 

First thing on nostart.....is always check for blown fuses first....
that and tight battery cables.........90 % of the problems between these two...

At this point....I would be reseating everything electrical....

batt clamps remove clean....reinstall tight...
make sure the different body and block grounds are intact and good...
maybe even sand and reseat those.

then try start....

next I would go thru and reseat and maybe even swap around the relays.....efi....fuel open relay, ect....

try start..

Next would be go restab all the fuses on the truck, especially the efi, am1, am2, ignition ones...
carefully inspecting each one.

If ecm area had any condensation/or water problems......
then pulling ecm connectors and use electrical cleaner and reseat....

ONly thing electrical after this.....is ignition switch itself could be wore out...or on its way out....



Next I'd jump to fuel.....

stick a long hose on your fuel regulator return line.......crank and see if fuel shoots out......


If fuel pours out.......then I'd jump to engine sensors......

like the crank sensor.........if thats bad....its zero go.....

 

wuz up ost funny thing i swapped the efi relay with the power relay truck started ran 6-8 minutes than died out had to restart with starter fluid it started ran 6-8 minutes than died kinda suspect fuel pump

 

Yeah mine is starting to take a couple different cranks to start at odd times.

I think that is also impending pump failure.......and its a denso bought from denso in cali only couple years old.


Excessive ethanol in the gas over 15% could cause similar...