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Discussion Starter #1 (Edited)
this is for my fit...but its a similar engine to the r18, so i figured id ask.

i changed my battery back from odyssey pc680 to the OEM battery. car was running fine with the pc680. went to start the car when i was done and it woudlnt start. everything in the car is working...except there is no spark. (after cranking i connected my scanner to see if there was any codes...p1103 map sensor high...i cleared it and no codes have returned since)

i tested EVERY fuse, all are good.
checked for voltage at the wires feeding the coils (white wires with stripes) and there is no power when cranking the engine.
bypassed my AEM FIC to eliminate that as a problem, still no spark.
checked voltage at the ignition wires on the steering column, they have power too.

im at a loss.
im 99% sure the coils are fed directly from the ECU, but i find it hard to believe that the ecu is fried from simply changing a batterry. wires never crossed, no sparks, nothing like that.
is there somthing im overlooking?
i know a bad crank sensor would have similar symptoms..but id find it a huge coincidence if that went bad doing a battery swap.

trying to avoid bringing it to honda cause it turboed and has a piggyback... theyll probly f*** more s*** up than fix it. and they want almsot $600 for a new ECU+programming..so thats my last resort.

here is a link to the jdm fit ignition wiring diagram. it is mostly the same except the US fit only has 4 coils/plugs....so just ignore the 4 front ignition coils.
Wiring Diagram
 

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usually the coils have a constant 12v feed and the ecu grounds it to fire. Check and make sure you have a power on fuse 9 or 7
 

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by the way, I know people are real big on disconnecting the battery to "reset" things but I've been working on cars for a long time and I never disconnect the battery even when I'm changing it, I jump it and swap the battery out to avoid problems like this.
 

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by the way, I know people are real big on disconnecting the battery to "reset" things but I've been working on cars for a long time and I never disconnect the battery even when I'm changing it, I jump it and swap the battery out to avoid problems like this.
the only reason youd want to change the batt. with the car running is if you dont have your radio code. Other than that your not gonna hurt anything by disconnecting the battery. Its actually easier to "fry" your ecu if you do it with the car running...

your ecm could be fried. check for a 5v reference somewhere if you dont have it than its your ecm.
 

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Discussion Starter #5 (Edited)
usually the coils have a constant 12v feed and the ecu grounds it to fire. Check and make sure you have a power on fuse 9 or 7
ive checked every fuse, but ill double check and just replace the ones related to the ignition system though.

by the way, I know people are real big on disconnecting the battery to "reset" things but I've been working on cars for a long time and I never disconnect the battery even when I'm changing it, I jump it and swap the battery out to avoid problems like this.
i didnt do this to reset teh ecu, i had a battery relocator kit on the car..wanted to remove it cause the pc680 cant keep up with the cold temps weve been having in the northeast.

the only reason youd want to change the batt. with the car running is if you dont have your radio code. Other than that your not gonna hurt anything by disconnecting the battery. Its actually easier to "fry" your ecu if you do it with the car running...

your ecm could be fried. check for a 5v reference somewhere if you dont have it than its your ecm.
i checked for a 5v reference output for the crank position sensor...and came back good.

havent checked ignition wires for a 5v reference yet though.
if a ecu was bad though, woudl it have all the other functions? cause my scanner can connect to it, no CELs, andall dash lights are working.
 

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the only reason youd want to change the batt. with the car running is if you dont have your radio code. Other than that your not gonna hurt anything by disconnecting the battery. Its actually easier to "fry" your ecu if you do it with the car running...

your ecm could be fried. check for a 5v reference somewhere if you dont have it than its your ecm.
I said jump the battery not change it while the car is running. I take it you don't work on benz's often or you'd know why I do that.
 

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Check the underhood fuse box for an ignition coils relay. Its powered by fuse 18. Swap out the relay with a known good one.
If still no go then pull the relay and check for battery voltage on pins 2 and 4. Pin 3 should be battery voltage with the key off and should drop to 0 volts while cranking. Next check for good continuity between pin 1 and one side of the coils.
 

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Discussion Starter #8
fixed this. a wire that is part of the battery wire loom was completely pulled out of the harness plug. inserted the pin into the harness plug and it started right up.

note: pull gently on wire harnesses
 
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