O2 Sensor Changed, Eml Still On

CHARL13

Hi all

This one has the VX guys scratching their heads so I thought I'd try here. I had my EML come on a couple of weeks ago, fault code P0141. I replaced the post cat O2 sensor with a direct fit one and the problem reoccures. I have had the multimeter on the wire harness connector and it isn't reading any volts on either of the 2 heater circuit pins when the ignition is on but the engine off. Has anyone come across anything similar?

The full story can be found here http://www.vx220.org.uk/forums/index.php?/topic/95034-o2-sensor-changed-eml-still-on/

MikeS

step 1

Ignition OFF
Disconnect wiring harness connector from:
B118 Sensor - Oxygen, Exhaust, Heated 2
Remove electrical component from socket:
K18 Relay - Engine Control Unit
Connect fused jumper wire to:
K18 Relay - Engine Control Unit

Socket connector colour BNPK
&
Battery voltage
Measure voltage between the following terminals:
B118 Sensor - Oxygen, Exhaust, Heated 2
Wiring harness connector (wiring harness side) terminal 4
&
Ground
Note:

Wiring colours: BK=Black, BN=Brown, BU=Blue, GD=Gold, GN=Green, GY=Grey, OG=Orange, PK=Pink, RD=Red, SR=Silver, TQ=Turquoise, VT=Violet, WH=White, YE=Yellow,
L=Light, D=Dark

greater than 11 V

step 2

Work Order Description Nominal Value

Disconnect wiring harness connector from:
A4 Control Unit - Multec
(Wiring Harness Connector X22 )
Ignition ON
Measure voltage between the following terminals:
B118 Sensor - Oxygen, Exhaust, Heated 2
Wiring harness connector (wiring harness side) terminal 3
&
Ground

less than 0.3 V

step 3

Ignition OFF
Measure resistance between the following terminals:
B118 Sensor - Oxygen, Exhaust, Heated 2
Wiring harness connector (component side) terminal 4
&
B118 Sensor - Oxygen, Exhaust, Heated 2
Wiring harness connector (component side) terminal 3

5 ... 20 Ohm

step 4

Measure resistance between the following terminals:
B118 Sensor - Oxygen, Exhaust, Heated 2
Wiring harness connector (component side) terminal 4
&
Ground

greater than 500 kOhm

do these things and tell me where you fail !

CHARL13

Many thanks for the reply. Because of the distance between the battery and the relay, For T01 I measured the resistance between the relay connector and the wiring harness pin which didn't give a reading. So it's looking like a broken wire between relay and O2 connector?

MikeS

simple solution is a jumper wire

just splice into the wire and run a piggyback wire

see if you get any joy !

CHARL13

Ok I have done T01 as described and it failed. I have done a bit more digging, I can pass a voltage between relay K18 pin 1 and connector X2 pin 1 ok. I can also pass voltage between X2 pin 7 and O2 sensor pin 4 (B118 in the diagram).

Here's where it gets weird, the corresponding half of X2 has a red and blue wire coming from pin 1 (can't see this on the diagram) but nothing coming from pin 7? Is pin 1 and 7 bridged inside the connector? How is the voltage supposed to get to the O2 sensor? :wtf:

Much appreciated

MikeS

also remember the post cat sensor should not affect fuelling

the difference is hardly noticeable in performance and no effect on mpg

are you suffering from any other problems ?

CHARL13

Other than the EML being on there isn't anything major. It is slightly hesitant under acceleration, but I'll be putting it up for sale soon so it's something I want to get sorted. More annoying than anything as nothing changed before it started happening.

vocky

on some vx220's there are two lambda sized sockets on the nsr subframe, one works fine, the other doesn't

is it possible you have the wrong one connected ?

CHARL13

vocky said:
is it possible you have the wrong one connected ?

Hi Vocky

I have thought about this, I tried the sensor in both with no joy. Looking at the color of the wires I think it's in the right one.

I spent yesterday checking and cleaning all the electrical connections mentioned in the diagram and I am now getting between 2 and 3 volts from terminal 4 of the sensor connector which is a step forward, I just need to find the missing 8v now! The only connector I can't get a definitive answer of is X33. I think it's the coil pack connector but I can't be sure?

drpau

vocky said:
on some vx220's there are two lambda sized sockets on the nsr subframe, one works fine, the other doesn't

is it possible you have the wrong one connected ?

Just changed my rear lambda sensor, didnt notice initially that there were two identical plugs, I didnt pay too much attention to which was which when I removed :crazy: as I had only seen 1! Now Im in a quandry as to which is which, seems due to the way the plug is designed you could also plug them upside down! Question is, will I cause any damage by starting the car like this or will it be OK?
One plug wire goes off towards the engine (towards the part of the loom that is nicely clipped around the engine in a plastic casing), is this the one I should be plugging into?? Feel like a nob right now for not paying more attention :oops:

drpau

Seems I plugged it into the correct one as its running fine with no EML :clap: This was the longer of the two, the one which heads off towards the engine.....

CHARL13

Well having tried another lambda sensor I'm still getting the same fault code. I think it's time to take it to Vauxhall as I'm all out of ideas.

Drpau, did you find out which way up the connector went? I assumed the catch with slope is the one that should lock it in place?

drpau

CHARL13 said:
Well having tried another lambda sensor I'm still getting the same fault code. I think it's time to take it to Vauxhall as I'm all out of ideas.

Drpau, did you find out which way up the connector went? I assumed the catch with slope is the one that should lock it in place?

On mine it could have gone in either way (seemed to have the same 'guide' on both sides of the plug)!! Have you tried flipping it over? Worth a go.... notsure.gif

CHARL13

Here's an update.

I checked as much of the wiring as I could and couldn't find anything wrong. I changed the sensor again, no joy. I found some white crusty stuff on the ecu pins which I scraped off and cleaned with contact cleaner, still no joy.

I've since sent it to Vauxhall to have a look. They have had it a week and can't find what's wrong with it either.

Changing the sensor is just a case of swapping the sensor and clearing the code isn't it? The TIS mentions reprogramming the volatile memories which I'm lead to believe is that same as clearing the codes with an OBD reader?

MikeS

white crusty stuff on ecu pins ?

sounds like a leaking capacitor or sommit

CHARL13

Yeh I thought it was strange, but as the ECU harness connector is missing it's weather shield I figured some water had got in there.

BTW, just got my copy of Black Ops, Woohoo.

MikeS

yeh but it wouldn't go white

it would go green

white is acid

CHARL13

Ah right I see. Just to double check Bank 1 Sensor 2 is the post cat sensor isnt it? I've read another topic on here that said P0141 was a faulty pre cat sensor?

MikeS

that is post cat sensor

replace sensor
if fault code is still appearing then check for resistance between ecu harness connection and sensor connection\
then either auto electrician or replace ecu