4dr_Noob

i just installed a stock exhaust back on my civic and it was driving great till i got near home then the d4 light started flashing and it was driving alot slower i think my o2 sensor was in a spot it could have got burned do you think that could do it or something else i mean what are the odds >.<

Former User

Check whether 7.5A dash fuse 15 is blown.

4dr_Noob

thanks i will

4dr_Noob

Ok well the fuse was blown so I replaced it drove it a little and it blew again except now the mph gauge stopped working and it got hard to shift

Former User

Sounds like there is a short in the heater power wire for one of the O2 sensors. Carefully check the wires.

4dr_Noob

What's the easiest way to go about that? Your talking about the the long 02 sensor wire covered in wrap? With the plug in and o2 sensor on it? Only way I can think to do that is cut the wrap check the wires and wrap it back? What happens if the wires are good? Well let me tell you this first the o2 sensor wasn't in the car last night then I redid the exhaust and my o2 sensor that goes in the first spot didn't reach so I had used the one that goes in the second hole since I do t have a cat yet I dot have a second one but that's the way it been for a year so you think the o2 sensor I hat sitting around is bad?

Former User

I can only guess. You probably pinched or damaged the heater power wire to one of the two O2 sensors. It's the Blk/Yel wire of both O2 sensors. If so, it would probably be pretty obvious.

Otherwise, purchase a multimeter or a short locator to find the short.

4dr_Noob

Thanks so much I'll check it out

4dr_Noob

Ok well I got a new o2 sensor Cause the other one was old and it had a burn hole in it with a wire showing could that have shorted it out causeing the fuse to blow causing all those problems?

4dr_Noob

i redid the o2 sensor and drove it over an hour and so far it hasnt messed up so i think its fixed although my pulsing problem started before the d4 thing and is still happening even after fixing the d4 light

Former User

The problems are related. Don't keep opening new threads on related problems.

Voltage test fuse 15. Click the fuses link in my signature.

4dr_Noob

oh i see i will test it in like an hour and post back and sorry about all the thread trouble :/ but thanks for all the great help

4dr_Noob

Ok tested all the fuses fuse 15 was at 12 volts off and 14.5 volts on all fuses were 14.5 volts besides starter signal fuse at around 17 and the wad lights were at 60-70 for all three fuses :/ I think we have a winner?

Former User

Almost all dash fuses should read 0V with the key off.

Please read the Fuses thread. Did you read it?

Post voltages measured on BOTH top test tabs of fuse 15 with the key in ON(II) (engine off).

4dr_Noob

Ok one second

4dr_Noob

Well I turned the key to where all the power is on but engine is off that correct? And the fuse reads 12.3 on both sides actually all fuses do

4dr_Noob

If I turn it just once which I think is what you meant it reads -0.02

Former User

This^ is the correct test.

Test the alternator:
1) Measure voltage across the two battery posts (key off)
2) Start engine. Measure voltage across the two battery posts again.
3) Same as test #2 except high beams and A/C are on, and vent blower is set on max.

Post the voltage readings for tests 1-3. Also watch whether the voltage readings fluctuate.

4dr_Noob

12.81 off... 14.4-15.1 flux on and 14.4-15.1 flux with the load on it

Former User

15V is too high and suggests that the alternator is bad.

4dr_Noob

i had autozone check it and they said it was fine >.< should i take it back?

Former User

AutoZone doesn't always get it right.

15V output by the alternator is a sign of overcharging.

4dr_Noob

well i have a lifetime warrenty from them for my alt do you think they wont replace it?

Former User

I've replaced my AutoZone lifetime warranty alternator three times. Only one time did they question my request, but quickly gave in when I told them that it tested bad in my hands.

If they test it and tell you that it's fine, tell them that the alternator intermittently overcharges and that you are worried that the battery will explode and that you want them to honor their warranty. But in reality, it's unlikely that they'll give you any problems if you stand your ground.

4dr_Noob

alright ill get on this thanks for the help you are seriously a huge help i appreciate it all!