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Discussion Starter · #1 ·
I just bought an 04 Civic LX, auto.

The ecu is bad according to everything I have read on the subject, and so I'm going to try to get a used ecu.

Here is my question.

I know from what I have read that the numbers on the old ecu must match the ecu that is being swapped.

Does ALL OF THE NUMBERS HAVE TO MATCH?

For example my ecu reads:
37820-plm-a72
2857-188137 M9

The ecu on ebay is
37820-plm-a73
2857-265240 M9

So do ALL of the number have to match if not then which numbers?

Thanks.
 

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Discussion Starter · #3 ·
Well, all I could get doing a search is this list [below] which is posted in just about every Honda forum. BUT, it don't list any 04 Civic with a PLM72.

The part number consists of three components:

Honda's part number for ECU, which is always 37820
Three characters (which are loosely related to the model of car/engine). e.g P72
Three characters (which are the revision of the ECU) e.g. A01
The middle three characters are the most useful to identify what the ECU is. Different generation ECUs may use the same characters. e.g. a P72 OBD I ECU is different from a P72 OBD II ECU. Here is a list of common ECUs:

PG6: 88-89 Integra (all makes)
PM5: 88-91 Civic/CRX DX
PM6: 88-91 Civic/CRX SOHC Si
PM7: 89-91 DOHC ZC (JDM 'EF' ECU)
PM8: 88-91 CRX HF
PR2: 89-91 ZC (Euro)
PR3: 89-91 JDM B16A EF8/9
PR3-J00 or J51: 92 JDM Integra B16A EF8/9
PW0: 89-91 JDM B16A EF8/9 DA6-XSi
PR4: 90-91 Integra LS/GS
PS9: 88-91 4 door Civic EX Auto
P05: 92-95 OBD-1 Civic CX
P06: 92-95 OBD-1 Civic DX
P07: 92-95 OBD-1 Civic VX
P08: 92-95 OBD-1 Civic D15 JDM
P0A: 94-95 OBD-1 Accord EX
P13: 93-95 OBD-1 Prelude Vtec
P14: 93-95 OBD-1 Prelude Si (non Vtec)
P27: 92-95 OBD-1 EG JDM Civic 1600 sohc
P28: 92-95 OBD-1 Civic Si/Ex
P30: 92-95 OBD-1 DelSol DOHC Vtec Si/EG SiR
P54-G31: 1997 Honda Accord 1.8 LS
P61: 92-93 OBD-1 Integra GSR
P72: 94-95 OBD-1 Integra GSR
P72: 96-00 OBD-2 Integra GSR
P73: 96-00 OBD-2 Integra Type-R (JDM & USDM)
P74/75: 92-95 OBD-1 Integra LS/GS
P75: 96-00 OBD-2 Integra LS/GS
P2N: 96+ OBD-2 Civic HX Coupe
P2P: 96+ OBD-2 Civic EX Coupe
P2E: 96+ OBD-2 Civic DX Coupe
P2M: 96+ OBD-2 NZ Civic SOHC VTEC
P2T: 99+ OBD-? Civic Si Coupe
P5P: 97-00 OBD-2 Prelude Type-S (JDM ECU)
PBA: 97+ US Acura 1.6EL
PCT: 98+ JDM ITR / CTR

My car is a 2004 Civic LX, auto.
 

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Discussion Starter · #6 ·
Make sure your alternator bolts are tightened correctly before installing replacement.

Interesting you said that.

The gauges all work upon startup. The engine runs rough, and after just a few seconds the alternator belt starts to squeal like a pig, then the tach, and temp gauge die, the engine smooths out.
 

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If the mounting bolts are incorrect/loose/something, it somehow damages the ECU. There is more info on civicforums that ezone posted.

He may be able to answer some of your questions.
 

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Discussion Starter · #8 ·
If the mounting bolts are incorrect/loose/something, it somehow damages the ECU. There is more info on civicforums that ezone posted.

He may be able to answer some of your questions.
I checked the alternator today, and the belt was loose as Hell. Looks like some idiot welded wing nuts to the adjusting screws.

No way to get those tight enough using your fingers. I had a large socket that worked to get them tight, which tightened the belt.

The computer worked well. Now the tach, and temp gauge work well, and I can pull codes. Oh, and after I cleared all of the old codes there are no new codes.

The engine wants to die if I let off the gas so tomorrow I'm going to tighten the idle adjuster screw on the throttle linkage just a bit [God only knows what the previous owners did].
 
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