99 Civic won't start, scanner cannot establish connection

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I have a 99 Civic that won't start, it cranks over fine but when you turn the key to the run position the fuel pump doesn't run. I found that when you turn the key to run that the check engine light doesn't turn off after a few seconds which should mean there is a code stored but my scan tool says that it cannot establish a connection with the vehicle. I had replaced the main relay a few yrs ago as that's a common issue on these Civic's from that era but also found there can be an issue with the ignition switch. It looks fairly simple to change out, it's the electrical part which is a separate piece that doesn't include the actual switch with the tumblers and I won't have to worry about having 2 keys or having it rekeyed to the car.

The switch when it fails the car can shutoff when you hit a bump in the road or if you have a lot of keys on your keyring which I believe GM also had that issue if anyone remembers. I do have a new switch on order and hopefully should be here tomorrow but was wondering if that could be preventing power to the ecu, I've checked the fuses under the dash and under the hood but all were good. I actually do have another ecu that was in the car when I bought it that is if I can find it, I've looked this evening and struck out, it's way too hot and I'm too tired to keep looking right now. The car is actually CA emissions and I replaced it with the most recent Federal one, I live in VA and they only test if you live in Nova which I do not reside there. I'm hoping the switch solves it but if not then I'll have to find it.

I haven't done this yet but there is a brown pigtail connector at the ecu that you can short with a paperclip and count the flashes on the light to read the code. I literally had taken this thing to the dealer a few weeks ago and had them replace the airbag inflater under the recall and really haven't driven it much since.
 
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Pull up the brake handle and confirm the brake light on the dash stays on while trying to start. That is the same circuit that runs most of the ECU stuff. Generally though if the CEL doesn't cycle on and then out when you turn key on and don't crank, that means the ECU has failed to boot up, often an internal failure.
 

Merek

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IGN switch is a very good place to start based on what you are describing.
I've did some extensive research and did find one other person having the same issue but everything else was tied to hitting a bump in the road.

I went to leave from work the other evening and had the car running, I put it in reverse to leave and it just died on me so it's still parked there. It's at my dad's shop which is no big deal and honestly it really couldn't have broken down in a better spot. I have my truck to drive but realized I still haven't renewed the tags on my other car so need to also get that done.

Another test I can do is figure out if the ecu is even getting power, being a Honda which are easily modified there should be wiring diagrams somewhere online. I guess I really shouldn't rule out the main relay but I've already replaced that with a Honda part so trying the others out first and go from there. I actually have 2x of these cars but the other is a '97 and while a lot of parts are interchangeable unfortunately not everything and the ecu's are different between 96-98 and 99-00. I once had an egr valve issue before with the 99 and swapped it over which fixed it but then had to buy one to replace it for the other car. I've also found the ignition switch is not the same part either, on my '97 they only sell the whole assembly which is around $140-$150 which means the lock assembly, electrical switch and also the switch itself and you'd have to use 2 keys or have it rekeyed to the car.

It's been raining crazy over the last few days but was able to mess with it some this morning before work but should be able to try the new switch and hopefully find that ecu over the weekend. I have found a used one on Ebay for a decent price but just hate that I might have to buy another one but they are getting harder to find so might be worth picking it up anyways.
 

Merek

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Pull up the brake handle and confirm the brake light on the dash stays on while trying to start. That is the same circuit that runs most of the ECU stuff. Generally though if the CEL doesn't cycle on and then out when you turn key on and don't crank, that means the ECU has failed to boot up, often an internal failure.
Thanks that's where I'm leaning towards now that the ecu isn't getting power, I'll be able to test it tomorrow, just need to figure out which wire is sending power into it but not a big deal as I can find the diagrams online for it, these Honda's are notorious for engine swaps and people use conversion harnesses all the time.
 

Merek

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I just found a webpage that listed both obd2a & obd2b so I saved it html for offline viewing and sent it to my phone. This car should be obd2a but will be able to tell by the connectors used.
 
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In some later Honda cars when the scanner is not able to communicate with engine side of things. By this I mean, you can communicate with other modules like the ABS or trans. The lack of communication is caused by one sensor been shorted to ground and the most common one is the MAP sensor. Just unplug it and plug the scanner.
 

wtd

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I would start by checking power and grounds to the ECU which of coarse requires a good wiring diagram. A no communication with the scanner usually means the ECU is having some sort of issue.
 

Merek

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I would start by checking power and grounds to the ECU which of coarse requires a good wiring diagram. A no communication with the scanner usually means the ECU is having some sort of issue.
Yes that's where I'm at right now, the new switch was delivered and I replaced it which was a huge pain in the rear. The switch itself was easy but one of the connectors also have 2 wires that you need to unpin and then insert them into the new connector but what Honda should've done is just made a pigtail connector that made it plug n play. I couldn't unpin it and had to totally mangle the old connector just to get them loose and broke one of the wires but I was able to splice on a new female spade connector which is all it was.

After the new switch there was no change, car cranked over fine and the cel wouldn't go off, I took a paperclip and jumped the two wires together at the ecu to count the flashes but the light stayed solid and noticed the srs light would stay on for a few seconds but then go off for 1-2 but then it stayed on but that could be part of jumping that connector.

The weird thing is after all that and removing the paperclip the fuel pump works and the car is now starting, I connected my scanner and it does connect and there isn't any codes stored... so right now I am leaning towards the ecu, I'm still looking for the other one I have but right now thinking of ordering another used Federal one off Ebay, new ones online from a dealer are $800+.

Right now I really can't see the pump being bad as earlier I couldn't connect to the ecu so that's a problem right there. The pump is easy enough to replace on these as it's under the back seat and something worth considering after I swap out the ecu.
 
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Whenever you have mysterious electrical issues on a older car a good place to look is for compromised grounds. A 99 Civic in VA the potential for crusty grounds is pretty good.
 

wtd

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Yes that's where I'm at right now, the new switch was delivered and I replaced it which was a huge pain in the rear. The switch itself was easy but one of the connectors also have 2 wires that you need to unpin and then insert them into the new connector but what Honda should've done is just made a pigtail connector that made it plug n play. I couldn't unpin it and had to totally mangle the old connector just to get them loose and broke one of the wires but I was able to splice on a new female spade connector which is all it was.

After the new switch there was no change, car cranked over fine and the cel wouldn't go off, I took a paperclip and jumped the two wires together at the ecu to count the flashes but the light stayed solid and noticed the srs light would stay on for a few seconds but then go off for 1-2 but then it stayed on but that could be part of jumping that connector.

The weird thing is after all that and removing the paperclip the fuel pump works and the car is now starting, I connected my scanner and it does connect and there isn't any codes stored... so right now I am leaning towards the ecu, I'm still looking for the other one I have but right now thinking of ordering another used Federal one off Ebay, new ones online from a dealer are $800+.

Right now I really can't see the pump being bad as earlier I couldn't connect to the ecu so that's a problem right there. The pump is easy enough to replace on these as it's under the back seat and something worth considering after I swap out the ecu.
I wasn't aware that you could jump wires on the DLC to count flashes on a OBD II car. We used to do that on OBD I vehicles. A 99 vehicle should be OBD II.

Intermittent problems are hard to diagnose sometimes.
 

Merek

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I wasn't aware that you could jump wires on the DLC to count flashes on a OBD II car. We used to do that on OBD I vehicles. A 99 vehicle should be OBD II.

Intermittent problems are hard to diagnose sometimes.
Yes with Honda Civic's 96-00 they are definitely OBD2, 96-98 is OBD2a and 99-00 OBD2b with the exception of the HX which is OBD2a for all of those years. There is a blue connector in the front kick panel where the ecu is located that you jump the two wires and you can count the flashes of the light to get the codes.

Both of my Civic's are HX models, I ended up just ordering the other ecu off Ebay, I'll check the grounds as there's only a few of them in the engine bay to look at and may just end up cleaning them and replacing the wires, evidently there's 3 of them, the negative off the battery, another that goes to the thermostat housing and then one more at the power steering pump.
 
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Yes the 3 or 4 little black wires at the thermostat housing are important, they ground the whole ECU system. Besides the bolt the wires are on, check that the two halves of the thermostat housing, and the bolts holding the housing to the engine are secure and not rusted. The ground has to pass through to the engine block.
 
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wtd

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Yes with Honda Civic's 96-00 they are definitely OBD2, 96-98 is OBD2a and 99-00 OBD2b with the exception of the HX which is OBD2a for all of those years. There is a blue connector in the front kick panel where the ecu is located that you jump the two wires and you can count the flashes of the light to get the codes.

Both of my Civic's are HX models, I ended up just ordering the other ecu off Ebay, I'll check the grounds as there's only a few of them in the engine bay to look at and may just end up cleaning them and replacing the wires, evidently there's 3 of them, the negative off the battery, another that goes to the thermostat housing and then one more at the power steering pump.
Ok, I'm not that familiar with the foreign makes.
 

Merek

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Just curious, you replaced the main relay, was it a factory part? Could be dead again.
Yes they were purchased new from a Honda dealer online and are factory oem parts which is typically how I roll unless the part is too terribly expensive or no longer available I usually stay with oem.
 
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i have seen several newer main relays with cracked solder joints.
and older honda pcm's suffer from bad capacitors.
open it up and take a sniff.
fishy?
crud on the leads and on the board under them?
if you catch it early replacement and minor cleanup with do.
otherwise make sure you have power and ground when the scanner cannot see it.
 

Merek

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Thanks everyone, I did finally receive the ecu yesterday but haven't had a chance to install it yet as I've been trying to repair one of our older machines at work where the motherboard died and also we had a new machine come in and literally did not come with any instructions on how to set it up so we've been sending emails to the company back and forth.

Soon as I get this other one swapped I'll check the grounds and report back.
 
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