MrTodd

Okay. I haven't made a post on H-T in a looooong time, but I decided to make this post in hopes that maybe it will help someone who runs into the same problem I just had in my little EH2. I'll try to be as detailed and informative as possible, if something is unclear please make a post and I'll try to clarify things.

Here's the scenario: it's cold outside (below freezing) and i'm driving my mostly stock EH2 ('92 Civic CX) to work on the freeway. Just before my exit, I suddenly get a CEL and lose all power. Checking to see if it's in limp mode, I pushed in the clutch and pushed in the throttle - nothing. The engine is totally dead. I coast to a stop, pretty close to my work, and call a co-worker to help me out. While he's on his way, my mind starts racing as to what could be wrong....

Here's my setup:
'92 CX Hatchy
-other than chassis/brakes/suspension/wheel mods, my car is stock...
-EXCEPT for now the 8-valve CX head is bolted to a D16Y8 block, overbored .040" w/p29 pistons and a D16Z6 tranny.
-mind you, this is a total waste of compression because the CX head detonates like hell.

Anyway.

What's the first thing to do when your car dies on the freeway? Check the basics. We all know this. So as soon as my car rolls to a stop, I finish making my phone calls for help, and get out and pop the hood. First thing's first, check the timing belt...





--As you no doubt can see, I already have the upper t-belt cover off. We all do it. Don't judge me. Also, I'm sure you noticed that the t-belt looks okay, it's not snapped, and upon further inspection it feels tight. Even so, it's still possible it may have skipped a tooth, or three, and I *could* have bent valves (even though that probably wouldn't give me a CEL, but still, it's worth checking). So what do we do? Check the camshaft timing....





--Unfortunately I had a hard time getting my camera phone in the right postition, but if you look closely at the center of the picture you can easily see the 3 plastic prongs located on the lower portion of the timing belt cover. If you didn't already know, these prongs should line up with your timing marks on the crank pulley. The crank pulley has a total of 5 marks on the outer rim on the left side of your alternator belt (the only belt you can see on my crank pulley). There is a group of 3 grooves situated together, and a seperate group of 2 grooves. When your #1 cylinder is a TDC (top dead center) one of the two grouped timing marks should line up with the plastic-pronged markers on your t-belt cover. According to the HELMS manual, this groove is painted white. Don't count on that though, our cars are too old for such shenanegans. Also, just an FYI, the cam gear should have the "UP" wording facing...well...up, while you're doing this.

Okay, although you can't see it in the above pic, the camshaft timing is dead on. So this is where I let out a huge sigh of relief. So, what could it be? At this point, you have a number of options, see if you're getting fuel and spark, and then go from there. Unfortunately, this is my only car, and I'm already late for work. Once my buddy arrives, we hook my car to a tow rope and he tow's me to my work.

Now. It's pretty obvious that the Check Engine Light (CEL) only comes on when something within the vehicle diagnostics, or emissions, is malfunctioning. The ECU gets a faulty reading from a sensor, circuit, or itself, and grounds the CEL, giving you that friendly yellow reminder that your car just took a **** in it's own pants. Luckily, once the ECU throws a CEL it also stores a code, indicating what is wrong. To find the code, let's resort to the trusty HELMS manual......





--The above page obviously highlights what a CEL code is, and how to find it... You are supposed to find a 2P connector plug, connect the two prongs via a jumper, and your check engine light is now converted to a blinking code light. Look at the pic below to find the list of all available codes related to the USDM 92-95 Civic.





--Okay. Anyway. Looking at the picture above the code list, you can see a diagram showing you the location of where this connector is. I found it in my car by removing the glove box, and looking here...





--As you can see, there are 2 seperate connectors plugged into a neon green holder. One is a 3P (three point) connector, and the other one is the 2P connector that we need to use.

MrTodd

Okay. Now we obviously need to remove the 2P connector from the green holder. I'll let you know, when it's below freezing outside, it's a HUGE pain in the *** to get the plug out. Even so, once you do, you will need something to jump the two pins together. In my case, I used a paper clip - I snapped it in half, then bent it, like this:





--Once you have everything ready, go ahead and insert the paper clip into the 2P connector, like this...





--Now you are ready to turn the ignition to the "ON" postition, and check for codes... (Before I continue, please note that according to the HELMS manual, it doesn't matter if you put the jumper in before or after you turn the car on. So, don't sweat the order.)





--As you can see, my CEL light is on. It's not flashing at all. It's just a solid CEL. I waited for around 30+ seconds and it's still on... Damn.

At this point you have to think about what you did to your car to screw it up. In my case, I didn't do a thing. No engine swaps, no ECU mods, no fooling around with wiring or sensors. Quite literally, my car just died on me, out of nowhere. Apparently i've got no codes. When I try and start it, it just cranks and cranks. Before I go poking around in the engine bay, guessing, I decided to look to the HELMS for help... SO. What's the next step if you get to this point?

Now, before I go on, I'm going to let you know that I know my **** with hondas. I was never worried that I'd never figure out my car problem, it's only a matter of time, but, THIS time I decided to rely SOLEY on the HELMS manual to see if it got me results with less of a headache. I must admit, that following the HELMS guidelines made things much more linear, thus allowing me to feel less rushed and more patient. I highly recommend sticking the HELMS instructions whenever you possibly can, it's just seems to make things less hectic I've noticed. Anyway, let's continue.

Let's look at the HELMS and see what it says...





--Looking at the above page seems simple enough. Apparently I have to go to page 11-32 since my engine won't start, and my CEL doesn't turn off. So let's go there...





--Okay so according to this, it's telling me to turn the ignition switch ON, jumper the 2P connector, and check and see if it's giving me codes. Well, duh, we already did that, no codes. So now, according to HELMS, we are supposed to REMOVE the CEL jumper and try and start it again.

Not surprisingly, my car didn't start. So, let's turn the car OFF..



Now, according to HELMS, I need to check the 15 Amp ECU fuse in the engine bay fuse box...



--Looking at the fusebox cover, we can see that the ECU 15A fuse is in the top-left corner of the box.



--Here we are with the fuse removed. Looks great to me. Let's go to the next page in HELMS....




--It's saying to inspect the ACG (S) fuse in the under-dash fuse box. Here's the fuse panel for reference....



--Now, let's remove the fuse...





--Fuse looks great. So, looking back up a few pics to the previous HELMS image, it's saying that we now need to check some sensors. Specifically, the MAP, EGR valve lift sensor, and T/A sensor (aka TPS). Now since we don't have an EGR on my car, we can forget that one. So, first things first... Turn the ignition back ON...

MrTodd

While the ignition is ON, we now need to unplug each sensor, one at a time, and see if it affects the CEL in any way. First is the MAP sensor, located on the top of the T/B...



--Unplugged. Now to check and see if the CEL is still on...



--Yup. Still is... Okay, now let's plug the MAP sensor connector back in, and unplug the TPS connector, like so....



--Check for CEL...




--CEL is STILL on. Figures. Okay, next step according to HELMS is to turn OFF the ignition, and check some voltage on tons of wires to see if there is a short... So, turn that baby off...



--Now make sure that you plug everything back in, like this...



--Looks good.

Now, let's cut to the chase. The fact is, in my case at least, I haven't TOUCHED ANY of the wiring in years, so the chance of it suddenly getting a short is pretty low, but there still is a chance. The next thing I did here was read over the entire troubleshooting process to see what the HELMS is actually trying to get at. Apparently, if you are having a solid CEL, even while the diagnostic connector is jumpered, (ie no code), there is a fault either in the MAP, TA sensor, Fuel pump circuit (most likely main relay), the ECU itself, OR the wiring associated BETWEEN all of the above. So, instead of the tedius task of checking voltages, which I can't really do without the silly Honda ECU harness anyway, I'm forced to stick with the simpler tasks first.


Now, given the information I stated above, let's skip the wiring testing and get on with the easier/faster stuff.... Let's take a look at the next page...



--At the very end of the flowchart, it recommends either replacing/checking the main relay, or the ECU. Since the chance of an ECU going bad is hardly common, especially since I haven't tinkered with anything, I decided to look at the main relay first. I could just replace it and skip this step, but I'm poor, so I decided to follow the instructions to test it properly... Here is the procedure, according to HELMS...



--According to the manual, the main relay is a basic relay that is controlled by the ECU. The main relay gives power to the fuel pump, AND the fuel injectors. Now, I forgot to mention that while I was in the process of turning my car off and on, it was easy to notice that the fuel pump wasn't priming. We all know that this is a classic case of the main relay going bad... Or so we think. So, let's check on that bad boy and see if it checks out. First step is to remove the main relay, this is where it is located in the EG chassis...



--It's the grey box with the brown(ish) connector plugged in.









--As you can see, there are some 7 large pins located on the connector side. Following the instructions above, we need to test it using a multi-meter. Here's mine, i've had it for a few years, but I still try to keep it in it's packaging when not in use...

MrTodd

Since I was at my work parking lot (I work at home depot), I decided to go in and make a simple wiring harness to test out my main relay. Luckily our tool rental department is full of useful junk, and I ended up with this...



--The picture below shows it all hooked up to my battery...



--As you can see i'm just checking to see if I'm getting voltage through my ghetto rigged wires. Also, i'm sure you noticed the rag on the battery.... Like I said before, don't judge me.

Next step is to see if i'm getting "continuity" through a few connectors.. This really just means that you're testing to see if the relay is closing the circuits properly. In order to do this, I set my multi-meter to test for resistance, like so...



--The readout is showing "1", obviously. This means that there is an infinite amount of resistance (sort of), thus there is no circuit present. If i were to touch the red and black testers together I'd get a very low number, like, 0.00001 or something. So, by following the directions in the HELMS manual, I give you these fantastic shots of me testing the resistance (or continuity) of each little circuit within the main relay...







--Each time I'd reposition the 12+ power and ground connectors, the relay would make an audible 'click,' switching the circuits around. As you can see by looking in the above pics, each test was successful. According to HELMS, my relay is good...

So... My car isn't starting, and apparently the MAP and TPS is good, and my main relay is good. This leaves the ECU... Unfortunately, I don't have a spare ECU to try out, and I really don't want to spend money on one unless I know for sure that it is busted. So, instead I opted to just go ahead and buy a new main relay. I mean, maybe it's just an intermittent problem with the relay? So, I headed off to the dealer (my little sister let me borrow her car) and bought a new main relay. They had plenty in stock apparently. My total came to $70 after taxes... Ugh....

Here's the new unit.







--It looks a little different, but I verified the P/N's twice just to make sure it is the right one for my car. It is. So, let's plug it in and see if she starts up...



--Quick plug job.





--Ugh.......... It's a no go. I still have a solid CEL, no fuel pump priming, and needless to say, the engine still doesn't start.

MrTodd

Okay. No worries. Let's think about this... I started searching HELMS again, seeing if there are any other possibilities aside from the ECU being bad. After looking at some wiring diagrams, I noticed something... Take a look..



--The above image shows that the ECU, Main Relay, and a couple other switches are grounded by the "G101" ground. Perhaps this ground is all corroded on my car? Let's find out where this ground is, first of all...



--Ahhh... That looks familiar. It's the thermostat housing ground. I guess it's pretty important. Before I jumped to this one, I kept looking around for any other hot spot grounds... Found one more.



--Apparently the "G551" ground is connected to the fuel pump. Since my pump isn't priming, and my relay is NEW (ugh), perhaps my pump ground is all jacked up? Here's where the G551 ground is located...



--If you don't already know this, the G551 ground is under the driver's side carpet, bolted onto the frame where the seat rails bolt onto.

I decided to go home and get some fine-grit sandpaper, and then check out my grounds. First starting with the G101 ground. Here it is, in all it's glory...







--Now, after I sanded it clean.



--I also sanded the thermostat housing, where the ground bolts onto as well, but I didn't take a picture of the results. Either way, it didn't matter because I put everything back on and gave it a shot...





--Haha. Piece of crap. I got nothin.

Now, at this point I had already contacted ALL of my friends, asking if they had, or if they knew of anyone, who had a 92-95 civic or integra, in which I could try their ECU out. Luckily, right after I finished working on this ground, one of my good buddies came through. His little brother has a '93 Civic LX, 5spd. Sweet. Here is that hard *** machine...



--And below, my buddy Nate removing the ECU. Nate's a kick *** dude.





At this point I decided to remove my ECU. Here's how you do it.... First, disconnect the negative battery terminal, like so...



--Then locate the ECU, (on the passenger side, on the right side wall of the floor board) and remove the 4 bolts holding on the metal plate/shield whatever thing...



--Once those are out, pull the ECU out so you can get to the connectors...





--Unplugged and it's out. As you can see, the Civic CX comes with a P05 ECU. Look below for the LX ECU..



--The P06 ECU comes from basically all DX/LX 5spd, 16 valve 1.5 Liter Civics ranging from 92-95.

Anyway, installation is reverse of removal. Plug in the new ECU, then reconnect the negative battery terminal.

Now, it's time to see if she lives...



--Ingition ON.



--What do you know... The CEL went away. The fuel pump is priming.. Hmm... And guess what, it starts too!


PROBLEM SOLVED!

In the end, obviously, my ECU decided to crap out on me. Apparently ECU's do die, sometimes for no reason at all. We all know that this happens, but it may come to a surprise that even a stock, un-touched ECU can still call it quits when you least expect it.


FOOTNOTES: If you have a solid CEL, it's either your MAP, TPS, MAIN RELAY, or ECU, OOORRR the wiring associated in between all of those items! This includes grounds!


Hope this helps those of you who get the dreaded solid CEL code. Good luck peeps.

MrTodd

....While I'm at it, I figure I might as well show you how the new main relay fits. If you read above, you could see that the new relay is shaped differently than the original - enough to the point where I began to question whether or not it would fit. Take a look....



--First remove the entire under-dash cover for easier access to the main relay area like so.

Next, position the new main relay so you can bolt it in, like so...



--Let me just say, that this is a HUGE pain in the butt. It's really hard to get your hands in the right position, while putting in the bolt. Ugh. Anyway, obviously I got it in. Once it's bolted up, just plug in the harness, and it will look like this...




On a final note, the newer main relays are longer/taller than the older style.. So getting the harness plug back in really sucks. Be careful, and ease the plug back into the relay, there will be a bit of tension on the harness wires, but once it's plugged in all the way nothing will be stretching anymore.

That's it. Pretty straight forward.

HTH.

Ya Digg

I read the whole thing, you did a very thorough job Great thread.

You could probably pick up a CX ecu for very cheap off someone on here.

This should be stickied in the Check engine light thread for everyone to see when they get a solid CEL.

MrTodd

Thanks for your input, I appreciate it.

Yeah, I just gave in and went ahead and bought a virgin P28 ECU. I figure i'll just buy a D16Z6 this spring as a cheap replacement to the CX engine, this way i'll already have the ECU... Until then, I guess I'll be driving around with a CEL on after all. Haha. But as long as it runs through the winter I won't complain.

z6hatchboy

agreed, great write-up/tutorial on troubleshooting and flow charts. Im sure itll be of good use to someone here. I wouldnt have thought the ecu though, but hey "it could happen"

saywhat

Lol, I wish everyone did write-ups like this, plenty of pictures, and plenty of frustration.

Riced-EL

Great thread!!! Very detailed

Unseen Racer

GREAT thread!

andoxviii

iTrader: (1)

Very nice read. Thanks for putting some effort into a common issue on h-t.

nello a.

i have seen Q31 burn on a ecu many times, but never a crapped out ecu.
u are one of the few.

2000EX WhiteMagic

Very helpful, great job A++

wangkata

nice thread very well detailed on how to diagnosed...good info indeed.....

SHG_Claudio

Very nice man, good job. How much ya pay for a new ECU? Im amazed the P28 works in your CX, how is that?

MrTodd

I paid $80 for the P28. Still haven't plugged it in because I haven't recieved it yet, all because my roomates left for the holidays, and I wasn't home to sign the package when it came (work, ugh). Anyway, basically any OBD-1 ECU from Honda (that fits, at least) will run without any MAJOR problems.

With the P28, I'll just be getting a few codes while it's driving, which will most likely result in it running in open loop mode the entire time. No big deal.

Just think of it this way: all 92-95 D-series engines share the majority of the same sensors, thus allowing the ECU's to be able to 'understand' all the values necessary to run an engine. The only differences between the D16Z6 engine (which uses the P28, of course) and the stock CX motor (D15B8, using a P05 ECU),in terms of engine sensors/wiring differences, would be the addition of the VTEC solenoid and a 4-wire heated O2 sensor. All other sensors are essentially the same. Thus the ECU will have no problem running my motor, just like the P06 ECU ran my CX engine without any major hitch. (it just gave me an O2 sensor code, as it uses a 4-wire and mine is only a 1-wire).

Even so, my high compression 1.61 liter CX motor is not gonna benefit from the P28's fuel and timing maps in any way. But it doesn't matter because I see it as an investment for the future.

Hope that makes sense, I tend to drone on about details in the least effective way possible. Anyway. Thanks for the props!

SHG_Claudio

Oh, i see, thanks for taking the time to explain all that, I dont know civics that well haha. Why is your CX motor 1.61 liter anyways? You actually spent money on a bore? I thought it was stock? Then its a 1.5. But yeah, real nice job with the pictures and explanation, no questions there!

MrTodd

Thanks for the props man.

If you read above on my first post i listed the mods. The block is a d16y8 which has a longer stroke, which yields 1.6 liters. When i got the block i wanted to learn how to rebuild an engine, so i took it to the machine shop, over bored it .040", and dropped in Pm7 pistons just for fun. Thus the higher displacement and compression.

BlitzSix

Nice write up, although I'm not exactly sure why you thought an ECU failure is so unlikely, and yet you bought a brand new main relay despite it working perfectly when you tested it. Now you wasted $80, and you can't even return it. I think it would've made more sense to just try someone else's ECU first, or if you can't then buy one off craigslist for like $40, and if it's not the problem then you can just resell it for the same price you paid for it. Why didn't you just borrow your buddies main relay before buying a new one?

Great writeup though. My ECU also failed on my 92 LX like 3 days after I bought it. It didn't die while I was driving though, I was doing errands all day and it just wouldn't start up after I went in a store (which was, of course, the farthest I've been away from my house that day).

freakasis

if the cel was constant the ecu would have been the first thing i suspected.

MrTodd

I figured the main relay was just giving me an intermitten failure. It's funny though, here i was trying to be thorough so i could save money, but instead i jumped the gun and blew $70+ on the new relay instead of just being patient, and testing out parts first. I got frustrated because i couldn't find anybody who owned a civic where i could test out the ecu until a couple days later. For a moment i thought it would be faster and cheaper to replace the relay instead of buying an ecu (junkyards are stripped of honda parts here. believe me.). So you're right, i did waste money. Haha. I should've trusted the facts, not my gut instinct. Also, i wrongly assumed that since the ecu was completely untouched it would be unlikely to go out on me.

My car was out for 3 days before i got a hold of my buddy (i haven't talked to him in years) and found out he drove a honda. I got impatient and wasted money. So there you go. I posted this in hopes that people wouldn't follow my same mistakes.

The_Honda_Guy

Good job on the diagnosis man, you did everything the way you should have. ECU's generally don't just **** out, but it does happen every so often. It sucks too because that's usually the last thing you would suspect so you test everything else first and come to find out the ECU died. lol

m3tech95

helluva write-up!! i was having this same issue on a shell i bought for the last 4 days.. i finally got it started turns out 1 of the thermostat ground wires was broken & i didnt notice it cuz its covered by plastic.. this thread helped out BIGTIME ....<kudos>