mussamatt

I have an '05 lxse
I blew the engine a year and a half ago and have been replacing it at glacial pace since then. Now it's all in and it started and idles fare. I have been reading every post i can doing due diligence before posting, but I'm stuck. I think it may be in limp mode, idles fine just bogs down above probably 3000rpms in neutral. The engine light is on, tach doesn't read, temp gauge doesn't read fans come on, immobilizer light is flashing, OBD2 fails to connect. Once it managed to start without these issues. Only the battery light was on, it's not on during problem times. The battery isnt the greatest but I think it's good and I can elaborate on that if needed. At the moment I only have the valet key and a fob(dead battery). I have burped coolant and tried idle reset. I could see it attempting reset, idle would change and all gauges jumped. This would continue repeating every minute or so. I have added 4 gauge grounds from frame to batt and trans. Cleaned those contacts and removed paint on painted contact points, battery terminals, harness to engine, replaced with oem ground engine to rad support, unplugged and inspected 3 plugs connecting to ECM, checked most all fuses, and wiggled just about everything electrical. It would be difficult to get to dealer, it's been sitting for over a year and three wheels have stuck brakes.

Any suggestions would be appreciated
Would a honda reader make much difference?
Anyone know a mobile mechanic with honda diagnostics in Brighton mi?
If I get a used ECM does it have to be flashed in the car?
How do I know a used ECM is good?
Apologies if any of these questions have been covered, my head is gonna explode soon from all the reading and abbreviations.

ezone

Sounds like the PCM has shat itself....which is just an expensive symptom of another problem.

The most common cause of PCM this particular PCM failure:
See if the alternator mounting bolts were left loose, or the mounting bracket bolts were left loose. That WILL FRY the PCM.

Here's a copy of Hondas bulletin on loose alternator bolts http://www.underhoodservice.com/issu...ontentid=88560

Second common cause may be bad engine and trans ground cables.

If you don't find and correct the cause of the failure, the next PCM will also get smoked.

Here's another thought: If you ran it with a battery charger attached on high or boost, that could cause strange electrical stuff to happen due to high voltage.




The next PCM will need to be programmed for the immobilizer keys before it will allow the engine to run.. I don't know of any way to do it off the car either. Got a super well equipped local locksmith?


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Before you do anything else:
Disconnect the 4 wire plug from the alternator so it cannot charge.
Start the engine, see if any of the symptoms are corrected.
See if communication with a scanner is restored, see if gauge operation is restored.

If it all works this way, there may be hope for your current PCM.

mussamatt

Is the ECM and PCM the same unit?
Since it was down so long could it need to be flashed?
I will go out and try the alt wires.
The bottom bolt was tight and top bolt wasn't loose but I did get another turn on it.
I read the loose alt bolts thread, missed listing that in attempted solutions.
Thanks ezone for the response

ezone

Yes.

The usual OBD2 standard:
ECM = Engine Control Module (engine only)
PCM = Powertrain Control Module (engine and trans)


No, it doesn't work that way.
Report back if it acts right when the alt is unplugged, this could become interesting.

There's a bunch of threads on it here and elsewhere.
It's such a common problem that Honda put out that bulletin about it (linked in previous post)
YW.

mussamatt

No change
I didn't mention this before but the replacement engine didn't have an egr so I swapped the whole coolant/egr housing

ezone

So the PCM is probably toast.

Those affected gauges operate using serial data from the PCM instead of having their own wiring to sensors. So do some of the idiot lights..

The PCM also controls the field and voltage regulator in the alternator.

If the alternator becomes ungrounded it can backfeed the PCM, seeking ground through the 3 wires to the PCM. The voltage 'seen' by the PCM is now lower than the actual charging voltage due to the alternator lacking common ground, so it keeps trying to increase the voltage. PCM becomes damaged as the voltage rises, I believe permanent damage happens above something like 18volts.
Now in limp mode or failsafe.
PCM is now corrupt and the serial data is now garbage ....so the gauges can't act right (GIGO).
The immobilizer system also uses serial data for communication, so it goes nuts too.

Not a big deal there, probably just an early (01-03ish) engine.

mussamatt

What is my next step, short of buying an ECM and frying it?
The car has had mice in it, odds on a chewed wire in dash? Should it tear into and inspect.
The windshield has some bad spidered cracks, so maybe moisture in dash. I don't see any obvious water infiltration.
Someone mentioned a ground, I believe drivers side located close to airbag sensor, does that ring a bell. I've been looking but haven't found it.
Certainly clutching at straws, but gotta get all grounds clean, any hard to find grounds I can clean?
Should I expect to replace the alternator? Could its mounting surfaces need cleaning or are tight$&@ bolts enough to ensure quality ground?

Of course I've got it all on the line, I need this thing working.
I've got too much into it to and it has too much value against what I could afford otherwise.
My wife uses it for a daily driver as a teacher.
She is searching Craigslist for cars under $1000.

ezone

Figure out what caused the first one to go bad and fix it so you don't ruin the next one?


Both of these, and of course the ground cable attachment points on the body and transmission.

The engine and computer use these, but there are other grounds all over the car.


Not if it works correctly.

It was designed as using the bolts for grounding....but of course the physical contact points do need to be clean and tight. Rust and aluminum oxide are not good conductors of electricity.

One should expect anything at that price to need a LOT of work, and be in far worse shape then the Civic.

mussamatt

What is the trick or route to removing the ECM? Is it normally pulled through the glove box or up through the airbag? If air bag what do I do to avoid accidental activation?

ezone

Open the glovebox. Remove the glovebox.

It's easiest to cut the plastic brace above the hinge area, then remove the metal strip behind that. THEN you will have room to get the PCM out.


Check this thread: https://www.civicforums.com/forums/36-mechanical-problems-vehicle-issues-fix-forum/293259-how-do-you-remove-ecu.html
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