axelg89

Hi,

I'm having this problem where my car is not recognizing the o2 sensors and they are hovering around 450mV. I have now been searching the web and lying under my car for a week and still can't get this thing working.

The thing that confuses me the most is that I don't understand how it works. I get the hole principle of the 4 wire o2 sensor (heater +, heater ground, o2 ground, o2 omitted signal (0-1v)). The thing I dont get is the high and low signal voltage values. If I disconnect the o2 sensor and measure the pins from the ecu I get 4.4V on the low signal (why is that not just ground?) and 1.4V on the High signal (why is that not just powerless waiting for the o2 signal?). Can someone explain this to me?

Regarding my car I've done the following:
1. Measured between low and high signal with o2 sensor when running (constant 0.89V)
2. Connected ground wire on o2 to car ground and measured high signal (fluctuated between 0 and 1V then). Computer still reads 450mV.
3. Checked Connection between pin on pcm and o2 connector. All good
4. Grounded high and low signal, voltage in HPT dropped to 0-4 mV.

I dont understand why this is not working, seems like the PCM is Reading the signal (number 4), the pins have Connection (3), and o2 seems to be working (2). Any clues?

Very grateful for any assistance, this is driving me crazy.
// Axel

Bowtie316

iTrader: (1)

Did this ever work right or is this a conversion that you are trying to get up and going? If it is a conversion, I would start by checking to make sure they are pinned correctly at the PCM and ohming out the wires between the pcm and o2 sensor connection.

axelg89

This is a swap so never worked in this car.

Already checked the connection between the pins on the pcm and the o2 sensor connector (number 3 above) and they look right...

Bowtie316

iTrader: (1)

What I mean is, check the length of wire for continuity and double check that it is on the correct pin at the pcm. Which PCM are you using?

axelg89

I'm using a 2002 Camaro PCM, harness (modified by me) and ls1 from the same vehicule.

I checked the entire length (full connection between the ends) and the pins pretty much have to be right as I never removed them when modifing the harness. The pins are also checked and they go to the correct numbers.

Now I Went through all the Connections to the pcm and I found a pretty bad mistake. I previosly fed the PCM with 12V+ into RED 46, MIL light that provides ground when there is a DTC (which I've had the entire time). Can this have damaged my PCM? (the source was fused with a 15A fuse that didn't blow). When I removed the wire the p0300 and some EVAP and fuel DTCs went away...

But o2s still not working right

Russ K

iTrader: (1)

And if the O2 heater power & ground is good at the O2 connector, you need to replace the O2 sensors.

Russ Kemp

axelg89

So the low and high signal should have a voltage then? Why is this, does anyone know the explaination to this, thought the o2 sensor was gonna give 0-1V, how can this be done when you have a voltage exceeding 1V in both high and low signal?

I have some delphi 4w o2s that will be here in 2 days time.

Thanks for your replys

boostit5.3

iTrader: (3)

you will have a 12 volt + and a - for the heater circuit. the signal postive is the wire that goes to the ecu and the signal - doesnt have ground at the plug it gets its ground through the o2 sensor body when its screwed into the exhaust.

jimmyblue

iTrader: (11)

A working O2 sensor will bounce between 0 and 1V
(when things are working well, never quite to either
end; but things don't always work so well).

450mV is where the PCM jams the inputs to, when
a sensor fault is declared.

Make sure PCM grounds have zero difference from
block ground. There are a few braid straps on the
F-bodies that, if they're loose / open, will really
mess up stuff that depends on this difference being
nil.

axelg89

this is not correct for the ls1 o2 sensor. It has a seperate sensor ground wire. Your talking about the 3 wire type sensor.

As I said above a few times I get the basic function of the o2 and why my pcm flatline at 450mV. The thing that I dont get is why you have a voltage on the high and low signal when o2 is disconnected!.

When I now connect my new o2s (universal type 4w delphi) should I use the low signal feed as sensor ground and the high signal as signal?