No Check engine light 02 civic, I need electrical help


#1

I have a 2002 honda civic ex coupe. skipping the long story i rebuild the engine, replace the throttle body(used), crank position sensor(used), egr valve/solenoid(used). Then I payed to have the transmission rebuilt after crapping out 2 weeks after engine rebuild. The car still didnt run right and shifted hard and still had codes for throttle position sensor, egr, crank p.s. and electronic load detector so i took it back and he said it was electrical problems. the cel never did work i had assumed it was a burnt light bulb or it was disabled. He says maybe the ELD is bad so he replaces the under-hood fusebox with one from the junk yard with no luck then replaces the under dash fusebox with a new one, still no luck. Finally we buy a used ecm reprogram it and that didnt work so he tells me it has to be a short in the wiring somewhere and couldnt help me. i finally figured out if i unplug the TPS the car will run longer without going into limp mode and the hard shifting goes away but still shifts at higher than normal rpm and idles around 1200. suspecting a cut wire for the cel i change the bulbs in the instrument cluster and it still wouldnt come on. i chased down the most obvious wires but i cant find any obviously damaged or cut wiring. i also replaced the battery ground cable and im at a loss on what to do next. oh yeah one last bit of info i didnt think relevant but it also a code for O2 sensor but it’s unplugged and the cat replaced with straight pipe.


#2

Do you live in a state with smog inspections?

The fact that your check engine light doesn’t light up, you have a straight pipe instead of the cat and the unplugged oxygen sensor makes me think you live in an area with no kind of smog tests whatsovever . . . ?


#3

in Kansas city Missouri we do have smog inspections but i purchased the car already like that out of Kansas city Kansas


#4

So does that mean you bought the car with no cat and no CEL light?

Sounds like you and your help are just changing parts blindly without actually finding out the problems before you swap a part. Add that you are swapping in junkyard parts not knowing if those are any good either.

You need a scan tool so you can A - get the trouble codes and B watch for the sensor inputs to see what is and is not working. Doing anything else is a blind guess and any advice from us would be an educated double blind guess off the internet.


#5

The check engine or MIL light is turned on via the ECU making a connection to ground inside the ECU. Power is provided to the light on a yellow wire that ties to fuse 10. You should see 12 volts on that wire when the ignition is ON. The return side for the light is a grn/orn wire that ties to pin E31 of the ECU. To test the operation of the lamp simply ground the wire going to pin E31. If the lamp lights up then the problem with the operation of the light is inside the ECU. The lamp driver circuit is most likely damaged.


#6

This isn’t going to be helpful . . .

I think you made a major mistake by buying this car in the first place . . . ESPECIALLY if you knew about the straight pipe, unplugged oxygen sensor and inoperative check engine light

In addition to having a cat welded in, plugging in the sensor . . . and making sure it actually works . . . you’ll have to diagnose the reason the check engine light isn’t coming on

I hope you got this car for chump change . . . let’s say $500 or so


#7

+1
Buying a used car with sketchy alterations and expecting to get a well-running vehicle is tantamount to visiting a brothel in the hope of finding a virginal bride.


#8

actually $500 is exactly what i payed for the car and my (help) was using the MaxiSYS pro scanner i believe. the friend i bought the car from said he payed $4000 in repairs with no luck. From his stories I didnt trust his mechanic and suspected partially correctly a bad head gasket even though they supposedly did that job already i dont think it ever got the head machined. it wouldnt run right over 70 degree weather and the heater didnt work until i rebuilt the engine. i drove it very sparingly until then (august 2015) and i finally made it my daily driver where everything seemed fine for about a week or 2 when the transmission started acting funny and completely quit a few days later. I chalked that up to bad luck where now i had to decide after all that work if i should fork out $1500 to rebuild the tranny or junk it. eventually i chose the rebuild and here we are now with less than 100 miles on it since the rebuild and prolly 1500~2000 miles on it since purchase. while i agree its possible have put a faulty used part on the car. what is the chance that all 5 used parts are faulty and still throwing the same codes. I also made a jumper wire today and connected it from the green/orange wire from ecu E plug to green/orange instrument cluster b or blue plug wire and started the car and the cel light still did not come on. In fact the only lights that came on as i cycled the key and checked the connections on the jumper were the battery, oil, maint req, abs, P and brake. oh btw when i said egr in the original post i meant vtech, the guy i bought it from had the egr replaced prolly resulting from the cat job and yeah those ports were clogged when i rebuilt it.


#9

i will try and find my multi-meter tomorrow and check the yellow wire.


#10

From what you stated about the jumper wire test I assume you were testing for a bad connection on the return side of the circuit. If the circuit to the lamp is good and the problem is within the ECU you should see close to battery voltage with reference to ground on the grn/orn wire when you turn the ignition on. You don’t have to start the engine for the MIL light to turn on.


#11

I was under the impression the greeng/orange wire sent the signal from the ecu. So your saying the yellow wire both powers the cluster and sends the cel on signal? Again I will check the voltage when I get home from work.


#12

Ok, so i checked the yellow wire E24 and got 6.5V then i checked B21 green/orange on the cluster plug and got 0V and the same 0V on the ecu E31. i did accidently hit the turn signal and noticed that the arrow indicator light wasnt working however i did hear the clicking and the bulb flashed. i messed with it a little and also noticed everytime i engaged the turn signal the red light around the P symbol dimmed. oddly i didnt see a yellow wire that goes into either the a or b plug on the cluster, shouldnt there be one if thats the wire sending the signal from the ecu?


#13

Some of the voltage measurements make me think you may have a ground problem there OP. Double check that the ecu ground is properly grounded to the chassis, and there’s usually a sensor ground for the ecu in the engine compartment, usually in the area of the cylinder head. Make sure there’s a hefty ground strap installed and making good connection between the engine and the chassis too. And of course that the battery neg is well grounded to the chassis.

You seem to have a lot of problems going on there. I think if I had that problem I’d ignore all except one, focus on finding out why the check engine light isn’t coming on w/the key in “on” but the engine not started.

Modern engines btw will never run well if the pre-cat O2 sensor is disconnected. The O2 sensor is part of the air/fuel mixture function. You don’t need one with a carb, that’s a self regulating air fuel mixture by design, but with electronic fuel injection a pre-cat O2 sensor is mandatory.


#14

I’ll check that and I intend on putting a cat and sensor back on it if I can get it running right especially because I don’t want to have to clean the egr ports again.


#15

The data that I am looking at shows that power from fuse 10 in the dash fuse panel supplies power to the gage assembly via a yellow wire tied to pin A17. You stated that the shift indicator light dims when the turn indicator is on. If the dimming is real significant then this may mean there is a power connection problem. Check the voltage at pin A17 with things connected properly and working. You should see near battery voltage there.