really unsure..

Your P0031 code is for the heater on your front O2 sensor and the P0037 code is for the heater for the rear 02 sensor.
It seems weird that both heaters went out at the same time but a broken or shorted wire going to the O2 sensor will throw those codes as well.
That leads back to a wiring problem again.

that is my fear as well, especially after having both headlamp bulbs blow within a few days of install, at the same time as near as I can tell.
the radio came with the car so I have no idea of how it was installed. I did, however, add in some crossover's for the speakers (both F and R) as well as added some tweeters to the rear. Im not a bass guy, but I do enjoy a full spectrum of audio, so there was a small 400w amp powering a 10 in the back :)
Ill see if I can get the read on the - tomorrow. thank you for the diagram, it will help (I hope)
 
ok, so, I know its been a long time, I apologize for that.
suffice to say, quite a bit has happened since my last post as I lost my mother 4 days after
I have, however, been able to resolve the issue (I hope !)

Im going to try and break it down, but this is an "how I understand it" post, so I may make a mistake.

here is the series of events as I understand it, my amp + line got rubbed through a little and was grounding out against the frame, not enough to kill power, but it was enough to cause surges and ebbs to the point of damaging the Alternator, which in turn put more pressure on the battery. then it became a cascade effect, the battery would require more charging from a failing alt. eventually, the alt went completely bad, so I replaced it. but the damage to the battery was already done, so now with a new alt trying to charge a battery that literally cant be charged to capacity, putting a lot more strain on the alt (which Ive read are pretty weak to begin with) the only good thing is I got a new, not remanned, Bosche :)
so all that seems straight forward, now comes the tricky part, somewhere along the lines of the dual failures, several fuses got popped all at once, both in cabin and engine bay... but... somehow, everything other than headlamps still worked... ? my mechanic still cant figure that one out, according to him, the windows/locks shouldnt have worked as well as blower/ac and alarm. but, they did. only thing that was actually affected was headlamps and it seems (unknown to me) tail lamps also didnt work, but since I couldnt drive at night for fear of my lights going out, it was sort of a moot point since brake lights did work.

so, all this to find out my battery (just over 1 yr old when things started happening) had a bad cell and several fuses (and 1 relay, forgot bout that) got taken out in the crossfire between my alt and my batt.

as of writing this, the car starts and runs excellent and everything, including headlamps, work :)
 
so now Im back to no start.
but we are pretty certain we have it narrowed down to 1 of 2 things, bad ignition or bad wiring for an aftermarket alarm.

the car started and I was able to drive around the neighborhood for 15-20 mins (bad tires so didnt want to drive too far from home or too fast). when I got home, I started putting some things back together, which included the panel around the cabin fuse box. which I also had to move the wires for the alarm to get them tucked under said panel, after which, the car refused to even attempt to start. turn the key, plenty of juice, but as soon as I hit start click and no juice.

so my mechanic is coming by Sunday and we are going to completely go over as much electrical as we can without tearing into the dash.
will update then.
 
weeellll....
long time, I know, but this has been ongoing issue...
every time we get it narrowed down and replace something, another thing goes wrong. it got to the point of just parking the car until I could spend a little more time and money on it, thinking I might need a new wiring harness/ECU or both.
that said, I honestly think we have finally narrowed it down to the culprit.

several years ago, I had the starter replaced at a local shop. when they did so, they had cut the main power cable from the battery to put a new connector on it attached at starter. unfortunately, the first starter they got was for an auto (I guess they are different... ?) anyways, so when they got the correct starter in, the mechanic found he had cut the battery cable too short to accommodate the other starter. so he put a short strip of line to reach the starter.
sound like a mashup ? it is/was....

here is a picture of what this idiot did.

so I wonder how this guy expected this "repair" to handle 500amps ?
the entire time, this has been backfeeding my electrical. it probably explains how I could blow a cell from a gel battery and 2 standard batteries, all in less than 3 yrs time. including a battery I got just after my last post in this thread. which thankfully they just swapped with no pro-rate.
it also explains the blown fuses (about a dozen now) a few relays and 4 pairs of blown headlight bulbs.
 

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I got a new cable but its been raining all day and this is my first day off from work. if its not raining tomorrow Im hoping to be able to swap it around.
this should clear up a lot of the issues Im having, but I still may need a new starter.
 
So your only problem right now is the "no start" ??

Your car has been behaving otherwise ??
 
I was having a hard time seeing how that little piece of wire could cause all those problems, thinking it would just add a bit of resistance to the circuit and maybe make the starter motor weak.

But if that's coupled with a bad connection with some sparking and arcing going on then I can see the back feeding happening.
It looks like he just crimped the wires together with a butt connector too.

Either way, I hope this is your last problem and your car is up and running again.
 
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...unfortunately, the first starter they got was for an auto (I guess they are different... ?) ...

Yea, I guess they're different...



I didn't know that either but I would have figured it out before buying a new one.

Sounds like that mechanic really didn't know what he was doing.
He probably charged you double too, for doing the job twice.
 
ok, so we replaced the cable, and it cranked right up !!
even after sitting for almost a year she just purred right along !
we also found that his "fix" caused a lot of corrosion in the cable (only way it could happen according to my mechanic) so the weak connection + the corrosion at the starter terminal that extended a good 12 inches up the cord is why I was getting so much back feed.
Im in the process of ordering some pure copper crimp on battery terminals for both +/- sides.
https://www.electricalhub.com/generic--100-copper-battery-terminal-1

and also, just to be on the safe side, Im replacing the ground cable.
but as things are now, I can go out and just crank her up !
I know we should have began maybe at the starter, and he wanted too.
that is mostly my fault as I couldnt believe the starter would be going bad already after only a couple of years, especially since I sprung for the more expensive Bosch. I never even considered the wiring to the starter and what the shop mechanic did.

so I guess the lesson for me in all this, is stand aside, quit 2nd guessing him (or her) and let your mechanic do his job !! lol
 
Awesome,...
I'm glad there's another P5 still on the road.

not for long it seems....
today went out and got in, started her up to run to the next town, but it was pretty hot for once so I turned on the AC, and it sputtered really badly, then ran like crap. immediately turned AC off and it didnt make any difference. here is it running with AC off for almost 5 mins.

in 2nd vid (which wont upload for some reason... Im working on getting it uploaded.)
you can hear it sputters really bad when giving it gas, but will run smooth. I had it at 2k rpm and ran smooth, 2.5k and smooth, even took it up to 3k for a minute and ran smooth as butter, just sputters real bad on acceleration and idle is horrible (as you can see in 1st vid)

https://youtu.be/nsqRS4lDTS4
 
It sounds to me like the magnetic clutch might be kicking in and out ??

Maybe try unplugging it to see if it stops the noise.
Might give you some time to diagnose your problem.


 
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