CoolFoolIT

1998 Civic Dx Hatchback
obd2 ITR motor/obd1 P28 ECU


The symptoms I'm getting is that the car starts, and then dies with in 4 - 6 sec. Fuse keeps blowing with the ECU (one of the Plugs ) unplugged, and with integrated control unit unplugged.

I have a DVOM and know how to use it. Would someone be able to help me with wiring diagram for Blue/White wire from Battery power to Ecu/Fuse/Integrated control unit?

I have Tried following this not fully because of different cars/symptoms:
https://honda-tech.com/forums/tech-misc-15/starter-signal-fuse-keeps-blowing-2804535/
https://honda-tech.com/forums/honda-civic-del-sol-1992-2000-1/fuse-31-keeps-blowing-2919011/

Additional info:
I have cleaned out my IACV, FITV, Throttle Body a day ago,
my power windows are connected to the big Wht/Blue wire in the back of underdash Fuse box,
my ECU was all wet, and i might have taken in to close to the heater. Did try another one, no luck.

Again i need a detailed wiring diagram of Fuse 31 power to ground.

CoolFoolIT

Anyone?

Can anybody point me to a link to download a Repair Manual, free? I know for my E36 M3 i could just google it and it comes up every time.

Maybe I can download one somewhere for free?

Thanks!

NOFX

Okay, I've got the 1996-1998 Civic Service Manual from Honda here.

Page 23-55 says Fuse 31 is a 7.5A fuse (BLU/WHT) that protects ECM/PCM, PGM-FI main relay, integrated control unit.

The integrated control unit is the unit on the backside of the fuse box. IIRC, it's tied in to lots of weird little things. Even the wipers.

PAGE 23-62 (large image of full page)

Fuse 31
|
|
|---(Fuse/relay box socket)---Integrated control unit (PAGE 23-140 to 23-144)
|
|--- BLU/WHT----PGM-FI main relay (Relay testing, PAGE 11-157; Troubleshooting, PAGE 11-158)
|
|---BLU/WHT----ECM/PCM (Troubleshooting, PAGE 11-63)


I can set up my scanner and all if really needed, but it's a bit of a pain.

Sorry, it's against site rules to link to free downloads of the Helms manuals.

NOFX

Updated posts with page numbers for troubleshooting, etc.

CoolFoolIT

Does it show the conectors for BLU/WHT wire to/from ECU, and to/from PGM-FI main relay?

Why is it against the rules to post links?

NOFX

TsIt's not against the rules to post links. Just links to free manuals that you would otherwise purchase through Honda.

So you want the info for the ECU plugs (for BLU/WHT) and then the plug on the main relay?

CoolFoolIT

Yes. And if it has connectors that the blue/white wire runs through.

yes, i ment links to free manuals, does the site affiliates with Honda in any way?

CoolFoolIT

Thanks NOFX!

NOFX

The only manuals that would be of any help to you are the Honda manuals, as intended ones from Honda (like what I'm sourcing here). Yes, those are against the rules to link to free downloads here.

I'll get those pages up in a few minutes. Sorry for the wait.

NOFX

There are 3-4 plugs on the ECU btw. Which plug is it? There's the 32 pin (C132 ECM/PCM-A), 25 pin (C133 PCM-B), 31 pin (C134 ECM/PCM-C), and 16 pin (C135 ECM/PCM-D).

I see a BLU/WHT on plug C (C134/31 pin) for number 18. But the manual says that's the VSS.

Sorry, I'm used to my CRX manuals, where I have the electrical troubleshooting manual. Tons more helpful with full diagrams. Here I'm jumping back and forth all over the manual.

Sometimes you can find these manuals at Honda used for about $30 btw. Much much much better than the parts store counterparts like Haynes and Chiltons. Wonderful investment. I'll admit I've used the pdf versions before... and they can suck. Especially since some are purely images so you can't search them or page through quickly really. Sorry this is taking so much. Couldn't have been an easy fuse that's blowing.

C443, which is a 7 pin plug, is the plug for the PMG-FI main relay.

1-2-X-3
4-5-6-7

1 GRN/YEL2
2 BLU/WHT
3 BLK1
4 YEL/GRN
5 YEL/GRN
6 YEL/BLK1
7 WHT/BLK

Pages 11-41 and 11-49 to 11-52.

Integrated Control Unit/Fuse 31
Looks like it goes from fuse 31 to the ICU to the brake bulb check circuit?

The ICU just plugged directly into the under dash fuse box and has 14 pins. As you can see, pin 13 is your pin for the fuse 31.

Page 23-144 (trying to keep record in case I need to look back).

Bulb Check System (Brake System Light):

Cavity: A13
Wire: BLU/WHT
Test condition: Ignition switch at START (III)
Test: Desired result: Check for voltage to ground: There should be battery voltage.
Possible cause if result is not obtained:
* Blown No. 31 (7.5A) fuse in the under-dash fuse/relay box.
* Faulty starter cut relay.
* An open in the wire.

NOFX

Page 11-157 - PGM-FI Main Relay

Description
The PGM-F main relay actually contains two individual relays. This relay is located at the right side of the cowl. One relay is energized whenever the ignition is on which supplies the batter voltage to the ECMPCM, power to the fuel injectors, and power for the second relay. The second relay is energized for two seconds when the ignition is switched ON (II), and when the engine is running to supply the fuel pump.

Relay Testing

NOTE:
* If the engine starts and continues to run, the PGM-FI main relay is OK.
* Use the terminal numbers below; ignore the terminal numbers molded into the relay.

1. Remove the PGM-FI main relay.

2. Attach the batter positive terminal to the No. 2 terminal and the battery negative terminal to the No. 1 terminal of the PGM-FI main relay. Then check the continuity between the No. 5 terminal and No. 4 terminal of the PGM-FI main relay.
* If there is continuity, go on to step 3.
* If there is no continuity, replace the PGM-FI main relay and retest.

3. Attach the battery positive terminal to the No. 5 terminal and the battery negative terminal to the No. 3 terminal of the PGM-FI main relay. Then check that there is continuity between the No. 7 terminal and No. 6 terminal of the PGM-FI main relay.
* If there is continuity, go on to step 4.
* If there is no continuity, replace the PGM-FI main relay and retest.

4. Attach the battery terminal to the No. 6 terminal ad te battery negative terminal to the No. 1 terminal of the PGM-FI main relay. Then check that there is continuity between the No. 5 teriminal and No. 4 terminal of the PGM-FI main relay.
* If there is continuity, the PGM-FI main relay if OK. If the fuel pump still does not work, go to Harness Testing on the next page.
* If there is no continuity, replace the PGM-FI main relay and retest.

NOFX

A friend is curious if you have a/c on when you do this. It looks like some of this stuff might tie into the "heater sub-harness A", which might connect to a/c somewhere too.

His first concerns were if any cooling fans might come on as well.

Former User

Just to verify, is 7.5A dash fuse 31 blowing? It protects a Blu/Wht wire (not a Wht/Blu wire).

The Blu/Wht wire from fuse 31 runs to the integrated control unit, the ECU, and the main relay. Have you tried unplugging the main relay to see whether this prevents fuse 31 from blowing?

By the way, a blown fuse 31 should not cause a running engine to stall. Power from fuse 31 is only needed to start the engine, not to keep it running.

CoolFoolIT

I do not have A/C.

CoolFoolIT

Blu/Wht wire Correct!

If I unplug the main relay and fuse does not blow, what does that meant? My main relay is bad?

Former User

I prefer not to deal in the hypothetical. One step at a time. Do the test, and go from there.

Nobody123

I suggest you spend some time looking over the entire wiring for anything that looks unusual.

Former User

Bad grounds don't blow fuses.

Nobody123

....

CoolFoolIT

I was away from the car.


THE TEST
Did it - it blew the fuse, but the car does not start with Main Relay disconnected.

Question: The wire that supplies power to the Fuse 31 is Black/Red and it has continuity to ground being disconnected to the back of the FuseBox. I traced it and it goes to a double relay on the Driver's side side panel. It is holding on the same way the Main relay does - from the driver's side dashboard side panel. Don't know what that is?!

From there it goes to driver's side strut tower wiring conector, and turns into White/Black and goes to starter solenoid "S" terminal. The wire disconnected at the starter solenoid does not have continuity to ground! The solenoid S terminal has continuity to ground. Is this normal?

Former User

You are moving upstream of fuse 31 in the circuit. You need to move downstream in the other direction to look for a short. Remove fuse 31 and disconnect the main relay, all ECU connectors, and all ICU connectors. Then test for a short to ground on the Blu/Wht wire.

CoolFoolIT

I have Disconected the main relay, all ECU connectors, and all ICU connectors and tested continuity to body ground on the bottom of the fuse slot!

Maybe I did not mention it but with all disconected there is still short to ground on the fuse. Or I should have checked for short Blue/White wire in the back of the fusebox with it in the connector?
I have moved upstrem, because if the fuse is there, there
is continuity to ground from the fuse seat.
The Black/Red wire is providing power for that fuse thats why i went upstrem.

Again, the Starter solenoid - has continuity to ground on S terminal. Should it?
Also, how do I check relays? There is suppost to be continuity between at least 2 posts? or this is not always true?

Former User

AGAIN, drop your focus on the Blk/Red wire. The only way to blow fuse 31 is with a short to ground in the Blu/Wht wire. Locate that short and you'll solve the problem.

If you don't understand circuits, then you just need to trust me.

CoolFoolIT

Can I be checking at the FUSE? or the only way is at the back of the fusebox, with the connector plugged in?

Also I have two (2) Blue/Wht wires on one of the connectors, could you please post the connector with wire arrangements ?

And again, what is the Fuse 31 for ? What does the cuircuit do?

Former User

You can check at the fuse, but it must be on the Blu/Wht wire side of the fuse.

The Blu/Wht wire serves the main relay, ECU, and Integrated control unit. Your "unplug tests" indicate that the short is in one of the Blu/Wht wires rather than in the main relay, ECU, or integrated control unit.

The fuse diagram below suggests that a bad dash fuse box could also cause the problem.