Stupidity alert, what have I done? o2 Sensor related.

[berni29]

Hi

It's a long story, but to cut to the chase I cut the wires to my old (pre cat) o2 sensor (2003 car) while the engine was running. I got a healthy spark as I did so.

What damage have I done?

The longer version of this is that I replaced my RHS CAT section because of a blow that I just could not fix satisfactorily despite extensive welding. So I got a nice secondhand one, with o2 sensors attached and fitted that. I should have freed the o2 sensors off but I did not. Of course the pre cat (bank 1, 1) sensor gave a fault, no activity P0134. So its seized in properly and wont come out despite the advice of several you tube videos and bending of 2 quite strong 22mm crows foots. Thats when I stupidly cut the wires with the engine running. I was trying to keep the exhaust hot. Out comes that section of exhaust, and after a fight the old o2 sensor is out. So I remove the (known good) o2 sensor form my previous CAT and fit that.

Sure enough I have the same code P0134. And yes of course I have reset it. More than once. Can heating it with a butane torch when I removed it have killed it? Any fuses to look at? C2 30A looks good.

So what is my next step forwards? I was under the car with a multimeter this morning, but water dripping in my ear and the whole situation and meaningless of all the numbers and confusion of which pin is which caused me to give up.

You can tell I am just awful at car electrics. The car drives just fine by the way.

Any advice appreciated.

Berni

 

[cdmci]

Did you cut all the wires together? I guess so otherwise you wouldn't get a spark.... The question then becomes what damage may you have caused to the input circuit that supplies the power to the sensor and reads the result. I'm not sure there will be an easy way to find out, but if you replace the sensor and still get an error code then you could be in trouble.

If you have a circuit diagram and can figure out where the sensor wires end up then you could look at the voltage on the pins. You probably don't need the details but the voltages should be the same on each side.

Good luck....
C

 

[berni29]

Hello C

Yes I am (as well as being an idiot) rather efficient and cut all the wires at once.

I do not like the sound of the error at all. No activity sounds rather final.

I do have one more known working o2 sensor. However, that is welded in its bung on the old exhaust. Welded because it forms part of the unsuccessful repair to the old CAT.

I might try to get it out in one piece. It will be horrible to do, but I guess I deserve it.

Wish me luck.

Berni

 

[infrasilver]

For tracing the wires, I don't know the pin outs on the engine loom but you could easily trace them with a continuity tester to find out where they go and then on to the ECU pins to see if they all give signal/voltage still, compare one with the other.

 

[berni29]

Hi

Thank you yes, I will have to do that. I cut the No2 sensor out of the old CAT (ugh) and put that in. Same result. So it must be a blown wire or I have fried that part of the ECU. Well done me!

I think the right thing to do tonight is a couple of hours of Tai Chi.

EDIT: By the way, there is no chance that there is a fuse somewhere that might have blown is there? I have looked ion the net and the answer seems to be no.

Tks again

Berni

 

[deMort]

I have a test plan for that code on a 996 which i'm pretty sure will be the same , as its 5 pages long i need to email it to you , im sure i already have your email address but as forum names and email names are different i can't for the life of me find it .

I also have a wiring diagram for your car .. either way PM me if you need them .

Ok .. logically .. you had the same code before and after the mistake happened .. there's a good chance that nothing altered .. it's the same code which basically is the dme is not seeing a signal from the lambda sensor .

This would be the sensor .. the wiring ie broken signal wire or the dme .

You would need a scope to test the lambda sensor im afraid .. it's in the test plan the patten you will see ..

If no scope you would check continuity of the wires from the sensor to the dme .. it's the signal wire you need to test though .. at the sensor it will be a black wire .. white wires are the heater circuit with grey i believe an earth wire .

Wiring diagram will show you though .

Worst possible .. the heater wires are actually active when the car is hot .. these will have joined the signal wire briefly .. the voltage is similar IF the car is at operating temps ( 1.25 v heater wire voltage when hot ) ...

Unfortunately the amps won't be as the heater circuit will have higher amperage than the signal wire ... still possible for the dme to be ok though .. cars are designed for short circuits to some degree .

If cold then its 12 volts and there will be dme damage .

My hunch is that the mistake has not caused an issue and this is the same fault you first had .

Heating a sensor .. you can do it .. they get pretty hot as it is .. red hot at the base .. oxy/acet is fine .. not on the sensor body though .. again i doubt you got it that hot .

My money is on a broken wire or a dme fault that was already there .


EDIT .. stuff me i found out how to attach a file .. let me know if it works

 

[berni29]

Hello deMort

Email sent, thank you.

The car was up to temp so hopefully the ECU did not get the full voltage. I will do the continuity test to the ECU tomorrow. I'm pretty sure the o2 sensor itself is not at fault because I have tried two that I know worked.

If it is only 1.25v or so then I would be surprised if I have blown a wire. It may be that I have pulled on the connector and broken the sensor wire connection. Edit: Mind you I did see a fair spark.

I wonder why the test plan on that code for the 996 is so long? Sounds scary!

Hopefully I will soon find out. I am guessing repairing the ECU is not going to be cheap.

Thank you so much again!

Berni

 

[berni29]

Hello again

Well, I have done the continuity test and the three wires I tested, earth, signal and one of the heater wires all had continuity. Whoever at Porsche decided to label the different connectors 1-5 on the DME and then have A-E on the wiring diagram probably used to work for Lotus.

I have taken the DME out and had a quick look inside. Nothing looks burnt of otherwise unusual.

I wonder what the next logical step is?

deMort, thank you for your email! I am reading it now

Many thanks again

Berni

 

[berni29]

Hi Guys

Update, went through all the diagnostics, all the numbers checked out, the last step is replace (or fix!) DME.

Ugh. I'm trying to find a wiring diagram for the internals of the DME. I have examined it and cannot see anything obviously burnt inside.

Looks like I will be sending it off at some point. Have been quoted 300 all in.

Edit: Suggestions if anyone can point me in the best direction please!

Thanks again

Berni.