Fredo_p

After doing a lot of searching, I have the same horrible issue that many others have.

STORY TIME

At some point on my drive home from work my alternator adjustment bolt snapped. It lowered the alternator which took slack off the belt. 28 mi, 80MPH, A/C running, BOOM Limp mode. Didn't know what the hell was going on. Crawled in the express lane shoulder for a few min. Took 1 hr before a tow showed up ( still running the fan cause it was hot). Battery died.

Time to find out what's wrong.

Plugged OBD II to pull codes. Wouldn't connect. Had power but wouldn't connect. Time to fix it.

Found a loose belt. Crawled under and found alt not holding. Like any good home mechanic.....YOUTUBE TIME!!!

Replaced the alternator, belt, bolt. Even went and replaced the ground wires with 2guage from work(overkill? I think not).
I recharged the battery and started the car. LIMP MODE with FI relay click. Google tells me I'm f*cked and a dead ECU.

EBAY to the rescue!!

I triple checked that I had the correct part number and ordered one for $60. It comes in. P/N match. I toss that f*cker in and have it towed to the dealer. The mechanic comes out with the laptop and reader. 15min later.......IT WONT' READ. He spent 2 weeks and a total of 2 hrs and was never able to get the DLC to connect to the ECM and talk/pull codes.

SO, I have the car back in the garage. Have to find out why, with a replaced ECM, is the DLC not establishing a link. The DLC has power. The code reader turns on. But it just won't establish a link. The mechanic at the dealership thinks its a broken wire somewhere between the DLC and ECU. The problem is that the wire harness runs behind the blower. That means that just about the entire dash has to come out to get to it. HELL NO.

Going to start testing with a multimeter using this
I have a "copy" of the 2004 factory service manual but it's broken into a few PDFs and some have like 2000+ pages. Anyone know what kind of voltage and resistance I should be looking for each pin/wire?

Also, I had a hard time finding the DLC connector diagram to know what each pin goes to.

Any Ideas?

Fredo_p

I think I found a start. Have to check the continuity between DLC ground and body (pin 7). If there isn't then I have to check between DLC #7 and ECM/PCM connector 3 #23. If no continuity, then there is a break.

However, if I there is continuity when I disconnect ECM/PCM connector 3 and test DLC #7, then there is a break in the ECM/PCM wire (even worse).

ezone

You unplug the PCM and check continuity of the (3?) wires between PCM and DLC.

Follow the wire COLORS at the DLC. And note carefully, something like "red/wht" is NOT the same as "wht/red"

BACKPROBE so you don't ruin any of the tiny terminals inside the connectors at DLC or PCM

If the wiring is not open circuit then your used ECM is probably also junk. Just like your original PCM.

Assumption: Everything probably was fine and working until your alternator broke free, and that failure can't cut or ruin wires in the dash.

(So many of these cars end up in the junkyard because of a major $$$ failure such as: head gasket, transmission, or alt/PCM)

If you can find someone with an identical car you could plug your PCM in and see if it will communicate with a scanner while plugged in a good car.

Fredo_p

I checked ground (black wire) at the DLC. It's good. I checked white/red, not red/white, and got 11.95v. It's good. I then checked blue white (#7) at the DLC. No continuity. Next step is to check the wire (LT BL) between DLC (#7) and ECM(E23) for continuity. If there isn't any, then I have an open on that wire and need to repair. If there is, then it's the ECM.

That's what I'm afraid of. There was an issue with the dealership. I have a 2004 civic. Honda decided to update the ECM, so the P/N doesn't match what the Honda system uses. It's an old P/N. So what's the catch? The new computer is $780. Ebay has them at $300-500. If the test proves its the ECM, then I need to find a pick n pull and grab me a computer and see if that works (granted they are a PITA to do).

The only "what if" scenario I can think of is the that on that exact trip home, I managed to run over a plastic water bottle that magically slammed into my car so hard that I could feel it in the shifter (5 SP). Not to mention that all my ground wires had only 3-6 strands of copper left to them so they had horrible grounds. But what could an empty water bottle do to my car that would cause any issue like that? Hell, it probably caught in the belt, pulled and snapped the bolt, and did all this. Not to mention many people don't understand that you don't tighten from the bolt that snapped but the one on top. The bolt that snapped is just a holder for the bracket that does all the tensioning.

I'm trying.

Fredo_p

Well, worst case scenario. Before I posted this, I went backwards on the troubleshooting tree. Tear everything apart, check the last thing first and go from there.

I have seats, center console, the entire lower dash, and panels removed. I just finished checking continuity between DLC and ECM E23......coninuity is good. AKA I got screwed on an Ebay order. Send it back? The seller is in TX, in the path of where the hurricane hit. SOOOOO, I'll have to wait till it clears to see if he can take it back and post office resumes operations.

Time to put everything back together and find a junk yard near by to pull a computer from.
I miss my 2000 EX cause of how simple it was to take apart. Granted I did kinda want to know what is behind the panels and see how hard it is to do since I want to run wires for speakers in the future.

ezone

Your ECM search is going to be for
04-05
1.7L
Non-VTEC engine (DX/LX)
Manual trans

My catalog resource looks like the car should use ECM# 37820-PLM-A15
Previous # looks like it probably ended in A14. I can't tell if that's what would have been installed in the car originally though.
And yea almost 800 donuts retail for a new one.





DLC terminals 4 and 5 are always grounds.
16 is always battery power. (OBD2 numbering, not Hondas numbering)

The rest of the wire positions are up to the manufacturers. Colors should be consistent though according to the diagram you posted..
is one helluva stretch. I'm not buying it LOL

Speaking as a troubleshooter, I'd starve to death if I worked that way LOL

Make your request, send it back and wait....


If it came from a junkyard or dismantler, most of the time they don't have any way to evaluate it before pulling it and shipping it. If the car ran at all they figure the computer must be ok, they mostly care about bad engine noises and if it can pull itself in a circle around the parking lot. Much of the time they can't even evaluate that since a lot of cars go in as crash victims.

--------

Pic from a recent loose alternator disaster that came into our shop (someone else caused it) This one not only broke the bracket, it wore the big bolt into a Z shape and stripped the threads of the cast bracket AND ruined the PCM.

Fredo_p

The old P/N that the 04 originally used, and what I ordered, was 37820-PLM-A13. Honda updated to A15 or A16. I have to call the dealership to find the exact number since it appears to be VIN specific or may AT vs MT.

Either way, all the Ebay prices are a few hundred more than the A13 which explains why it was so cheap and the updated number so pricey.

ezone

If buying brand new, it's A15.
There is no A16.

If buying used, 37820-PLM-A13, A14, and A15 all will work. It's customary for many used part prices to be approximately half of new retail price. Of course that can vary a lot too.


FWIW Majestic wants 543 for a new unit. That's wholesale price, like many other dealers selling parts online.

A new unit for your LX trim car is cheaper than others...... I just checked a few of the part numbers for a brand new PCM for a 04-05 car with VTEC (EX trim), is over 850 donuts.
The same part for a GX trim car (CNG fuel) is almost 1350 donuts.

Fredo_p

Yeah, VIP told me a new one was 780.

Both the service clerk and the mechanic asked me if I was mechanically inclined and, if so, to just take it home and fix it myself and save myself the 800-1000 for the repair.

Although, I'm a bit confused. If he wasn't able to get it to link but had the manual, why didn't he end up checking to see if the line was broken or if there was continuity like I found out after reading the manual? I'm guessing it wasn't a money making car so they wanted it moved out ASAP.

ezone

Maybe because the allotted (paid) checkout time was up.

Nuts and bolts type work is one thing........ wires are another thing altogether. Electrical has always been like "the final frontier" of most mechanics' skillsets. Many can't even understand what it takes to make a light bulb work. Electronics eliminates most of the rest of those people.

Relatively few mechanics have the necessary skills/tools/expertise to diagnose mechanical problems accurately, and electrical stuff isn't even on the radar for 3/4 of the people in the trade. I'd guess 10-20% are truly competent and good at it, the rest just guess (read code, throw parts. Ugh.)


The acid test is going to be finding another car to plug your control unit into to see if it still does not communicate with a scanner. Short of having a known good control unit to plug into your own car, that's the next best check I can think of.

redrocket87

I didn't see an end result, just wondering what it was and was it fixed? I'm having a similar issue. One of the 2 Alternator mount bolts loosened off and the slack in the belt caused the Battery Light to came on. It happened as I was out and I made the short drive home and checked the Alternator and found that it was loose. I tensioned the belt and tightened the bolt, fired it up, but the light stayed on. So I disconnected the battery and let it sit for an hour or so and tried it again, no luck the light was still on. So I disconnected again and left it overnight and tried in the morning, still no luck! The light stayed on and won't go out, but a new symptom has popped up and that is sometimes when you go to start the car now the Battery light goes out and the Engine light comes on and it turns over but won't fire. It will eventually start, but it does so in Limp Mode. If you shut it off and start it backup the engine light goes off and the Battery light comes on, but the engine will intermittently momentarily stall and then keep running. It keeps up and then it will eventually go into Limp Mode and you have to restart it to clear it. We tried to read the codes, the OBD would not establish a link. On the 60 kilometer drive home it went into Limp Mode twice on the highway and once in town. I have a 2005 Civic Si-G Coupe with the 1.7L L4 SOHC 16 valves vtec.

ezone

Search this forum for "loose alternator bolts"

Many/most/all end up needing a PCM after finally correcting the alternator issues that caused it.

If the PCM cannot communicate with a scanner, it's probably too late to save it.

redrocket87

What would the ECU I'd be looking for? It's a 2005 Canadian Civic Si-G Coupe with the 1.7L SOHC V-Tec 5 speed Manual.

redrocket87

Typed previous before I saw your reply which PCM would I look for?

ezone

PCM = powertrain control module, engine AND Automatic transmission
ECM = Engine Control Module (manual transmission does not have electronic controls)


You need an ECM that is compatible with your exact car.
It will need to be from 2004-2005 Civic,
and the rest needs to match your engine/trans combo: D17A2 engine (that's the VTEC version of the 1.7L) and manual trans

Canadian/US market might make a difference too, but I am not familiar with differences there.


Used....try checking www.car-part.com
Not sure that works in Canada, but give it a shot

NOTE any used ECM you buy will need to be programmed (immobilizer system) before it will let the engine run.

Make SURE your alternator problem is fixed, you don't want to buy a bunch of ECMs!

Check if you need an airbag recall done too!

HTH

Fredo_p

I fixed it a while ago. Just can't seem to find out how to update the post title to [Fixed].

Bought an eBay replacement and it ended up being bad. Went to a junkyard and got a good one. Reprogrammed and all is well. Now I have to figure out is the rattling from my tranny is the thrust bearing or input shaft bearing... FML

ezone

Title edited

Colin42

Does the noise go away with the clutch in? or with the clutch out?

Fredo_p

clutch in. Slowly getting louder over time. Either way its going to be a first dor me and a PITA since its cold out now.

Colin42

so input shaft bearing then

https://www.civicforums.com/forums/1...save-some.html

I swapped the trans in my gold 05 for an ex trans (sportier gearing, and no input shaft noise). I also changed the clutch, throwout bearing, etc while I was in there. Took me one long day to do it, and I had never done that job before. Got access to a garage that you can put a heater in and a couple buddies?

Also I bought that car in the fall with the noise and did the swap in the late spring once it was warm enough to work outside. Drove about 25,000 kms (15,000 miles) during that time as well. Never had a problem

Fredo_p

thanks