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Author Topic: What does this pipe do?  (Read 1226 times)

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JamesV6CDX

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Re: What does this pipe do?
« Reply #90 on: 14 March 2023, 13:19:34 »

Resistance down the wire from damage will be higher than a good wire. So comparing the resistance of all four wires between the plug and the ecu will confirm damage in a given wire. I suspect you will find the green wire has a slightly higher resistance to the others.

Continuity or lack off/open circuit will indicate a break but not internal damage... There being a subtle distinction ;)

Yes agreed I think Iíll check the resistance of all sensors and compare them. Get the full picture :y
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Migalot

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Re: What does this pipe do?
« Reply #91 on: 14 March 2023, 15:13:29 »

This info is probably of no use, but I went to the car and, with ignition only, I was able to clear all existing codes. The moment the engine started, however, Sensor Heater Circuit Open and Sensor Heater circuit malfunction both popped up.

I drove a couple of miles to the supermarket and got the above two PLUS O2 Sensor Circuit Malfunction and Sensor Circuit No Activity.

It's definitely running a bit lumpy at idle. Not too bad at speed.
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JamesV6CDX

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Re: What does this pipe do?
« Reply #92 on: 14 March 2023, 15:19:52 »

This info is probably of no use, but I went to the car and, with ignition only, I was able to clear all existing codes. The moment the engine started, however, Sensor Heater Circuit Open and Sensor Heater circuit malfunction both popped up.

I drove a couple of miles to the supermarket and got the above two PLUS O2 Sensor Circuit Malfunction and Sensor Circuit No Activity.

It's definitely running a bit lumpy at idle. Not too bad at speed.

Good to know

Is it today you collect the CTS?

Please can you make sure car is stone cold (Eg, has been sat overnight) when I See it? :y
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Migalot

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Re: What does this pipe do?
« Reply #93 on: 14 March 2023, 15:41:32 »

This info is probably of no use, but I went to the car and, with ignition only, I was able to clear all existing codes. The moment the engine started, however, Sensor Heater Circuit Open and Sensor Heater circuit malfunction both popped up.

I drove a couple of miles to the supermarket and got the above two PLUS O2 Sensor Circuit Malfunction and Sensor Circuit No Activity.

It's definitely running a bit lumpy at idle. Not too bad at speed.

Good to know

Is it today you collect the CTS?

Please can you make sure car is stone cold (Eg, has been sat overnight) when I See it? :y

Yes, I have the CTS!
When are you coming?
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JamesV6CDX

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Re: What does this pipe do?
« Reply #94 on: 14 March 2023, 15:52:58 »

Just need to make sure I can use the car, but I'm thinking tomorrow
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Migalot

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Re: What does this pipe do?
« Reply #95 on: 14 March 2023, 17:08:25 »

Just need to make sure I can use the car, but I'm thinking tomorrow

Sounds good to me. You have my WhatsApp number, so you can message me. :y
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Migalot

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Re: What does this pipe do?
« Reply #96 on: 17 March 2023, 20:08:20 »

Many thanks once again to James V6CDX for coming round to look at my car.

He changed the coolant temperature sensor and went about trying to trace the stubborn lambda sensor fault but, sadly, to no avail. Back to square one.  :'(

I am sure James will be along soon to describe the situation in detail. 
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JamesV6CDX

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Re: What does this pipe do?
« Reply #97 on: 17 March 2023, 22:29:05 »

Many thanks once again to James V6CDX for coming round to look at my car.

He changed the coolant temperature sensor and went about trying to trace the stubborn lambda sensor fault but, sadly, to no avail. Back to square one.  :'(

I am sure James will be along soon to describe the situation in detail.

Iíll just have a shower and chuck me clothes in the wash, and Iíll post progress and findings :y
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JamesV6CDX

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Re: What does this pipe do?
« Reply #98 on: 18 March 2023, 17:14:43 »

Sorry for delayed post, I had a shower and conked out on the sofa!

We had half a day looking at this yesterday. Here are the findings.

So - to start with a clean slate, we cleared the DTC's with the ignition on, but engine off.

Immediately (like, within a second) of starting the engine, the following fault codes appeared:

P0155-04 - O2 Sensor Heater Circuit Open (Bank 2 Sensor 1). Status:Present
P0155-08 - O2 sensor heater circuit malfunction (Bank 2 Sensor 1). Status:Present

For this reason, we can preclude any sort of fueling issue / imbalance, or erroneous input from any other sensors (such as CTS). Because the codes return immediately when the engine fires up,   the fault is, exactly what the codes say - a problem with the heater circuit for Lambda sensor 1, on bank 2 (The pre-cat sensor).

Forgetting what I already know about the car, and applying a logical thought process, I think "what can be causing this", and the main suspects I arrive at

A) Lambda sensor failure itself (failure of the heater) - usually most likely suspect, although not with this car.

B) Wiring problem between the ECU and the lambda sensor (second most likely suspect)

C) Problem within the ECU itself (as we know, highly unlikely and improbably, but mentioned for completeness).

Now applying what we know about this specific car...

1) We can preclude an issue with the sensor. Apart from the fact it's been changed a couple of times, just to be sure, we swapped the plugs - so, we plugged the actual B2S1 into the loom plug for B1S1, and the actual B1S1 into the loom for B2S1. More simply, we swapped the plugs for the two front lambda sensors. Despite doing this, and clearing the codes, immediately upon re-start, the same codes appeared - for bank 2 sensor 1 heater circuit.

So, based on this, we can 100% preclude this issue being with the sensor itself on B2S1.

So now we've ruled out the lambda sensor - let's look at the next most likely cause - a fault in the wiring, between the ECU plug, and the B2S1 connector pins.

Using the information very helpfully given by Dr G, we did the following tests, using a multimeter:

Bank 2 Sensor 1 (The one it's moaning about)

Pin 1 Grey (The live feed to the heater circuit) - a healthy looking 13.9 volts (engine running) - indicating there's no issue with voltage getting to the sensor?

The following were then tested using a multi meter on it's lowest ohm setting:

Pin 2 (Green wire) to pin 2 on X85 - 0.8
Pin 3 (Brown and Black) to pin 7 on X85 - 0.7
Pin 4 (Blue) to pin 9 on X85 - 0.7

On the face of things this looked okay, so we also tested it against one of the others (Bank 2 Sensor 2 - post cat) - and got exactly the same values.

I couldn't compare the bank 1 plugs, because the ECU Pins posted on here for B1 connectors didn't seem to match up (For example, X85/50 doesn't have any wire connected to it at the ECU end).

But as it stands, the values look fairly consistent, and don't indicate a wiring problem - although I still maintain it's the most likely cause.

We can rule out the ECU, as well as being indestructable - this one has also been swapped out, and the fault follows it.

The only thing I am unsure of, is the grey common wire feeding each sensor. At a first thought, it's clearly giving the sensor voltage which suggests that the circuit is okay. But, as DG says, it's fed from a common source - so, maybe is there a problem upstream of that source, between the common source and the ECU plug? I'm not sure what locations I would use to go about testing this, if so? (I'll ponder the wiring diagrams later, to see what I can see).

Because of (limited) access, I am in the mindset that the loom needs to be out of the car for a thorough inspection. And as we know, removal of that loom is not the most difficult job in the world.

I would like to identify and fix the fault, rather than "fit and hope" - but, we have found a loom from our famously known and trusted Heathrow based Omega breaker for good money, so given how strongly we can preclude the sensor itself, and the ECU - there is a serious temptation to just fit a known good loom - especially as the existing loom would have to come out to be thoroughly tested in any event?

I and I have no doubt Migalot would appreciate your comments and opinions, I feel we are SO close to resolving this problem, and it would be an unforgivable sin to scrap such a lovely and now fairly rare car (it really is in good shape!) for the sake of of what is a stupid electrical gremlin!

I don't mind going to Migalot and getting my hands dirty on / under the car, but I am the first to admit that whilst I get all the concepts, electrics are not my strongest point, and many heads are better than one. I really hope we can collectively get to the bottom of this and implement a permanent fix :y
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Doctor Gollum

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Re: What does this pipe do?
« Reply #99 on: Yesterday at 05:23:11 »

My money is on it having been pinched during the gearbox swap.

Fresh loom is the easiest starting point as the common connections are buried within the loom, and as you rightly suggest, it requires removal to inspect it so you may as well start there.

Having said that I would confirm that X3 is correctly connected. This is one of the round connectors next to the battery.
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JamesV6CDX

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Re: What does this pipe do?
« Reply #100 on: Yesterday at 06:30:08 »


My money is on it having been pinched during the gearbox swap.


Taking the "I couldn't possibly have done that" emotion out of the equation, this is actually a logical thought process which I too would seriosuly consider were I looking at this fault from the outside, knowing a box swap had taken place.

If the gearbox had been changed in bodge-it and scarper's backstreet garage, it would in fact be at the very top of my list. But having changed it personally (and carefully) I would be rather surprised if it were the case - I say this because I am very aware of the fact these cars are ageing, and take particular care around wiring and electrical connectors when I work on them.

You're right to raise it though, and it shouldn't be discounted.

In this case, I am not convinced. This fault wasn't present in the weeks that followed the gearbox work, and the car then ran for months without the fault code being constantly present, so if it were a trapped wire, it would have to have been slight enough to have only caused an intermittent fault, before then worsening. Had I pinched a wire (for example, in the bellhousing) I would expect the clamping forces to completely destroy it, rather than cause an intermittent fault.

I also ask myself, (given the fault code is constant for open circuit) how come the heater wire gets a healthy voltage, and the resistance between the X85 ECU plug and all of the pins on the sensor plug is consistent - to me this suggests the fault is upstream of the sensor wires, somewhere else in the loom - especially given that (as you say) the common connections are buried within it.


Fresh loom is the easiest starting point as the common connections are buried within the loom, and as you rightly suggest, it requires removal to inspect it so you may as well start there.


This I do definitely agree with :y I remember thinking the loom looked a bit man-handled when I very first went under the car to look at solenoid issue, before taking off the box. There were small tell-tale signs of poor workmanship, such as some cable shrouds missing, and routing of wires sloppy. This also furthers my case that a straight loom swap is the best course of action.



Having said that I would confirm that X3 is correctly connected. This is one of the round connectors next to the battery.


All three round connectors by the battery were disassembled, checked, and put firmly back together over the last couple of days. I've known them to be responsible for electrical gremlins before, so made a point of double checking :y

Migalot - I wanted to hear someone else say it, on the basis that auto-electrics are not my strongest point - but as there is agreement that the loom would have to come out for a proper inspection in any case, I say we go ahead and order / fit that loom we identified. It's from a breaker who has a 100% reputation on here and is very knowledgable with Omegas, so I'd say it will be a good purchase. It's really not that big a job.

And, most of all, it would be £85 well spent if it cures this fault, restores your trust in the car, and keeps (one of the better) Omegas on the road! :y

It would, of course, also be prime-time to replace that leaky cam-cover gasket, at the same time  ;) :y
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Migalot

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Re: What does this pipe do?
« Reply #101 on: Yesterday at 09:12:44 »

James: Loom just purchased from that chap in Harmondsworth.  :y
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JamesV6CDX

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Re: What does this pipe do?
« Reply #102 on: Yesterday at 09:32:25 »

James: Loom just purchased from that chap in Harmondsworth.  :y

Result, we just need to identify a good day to fit it, then :y
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LC0112G

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Re: What does this pipe do?
« Reply #103 on: Yesterday at 10:37:14 »

This is the circuit you need :

https://github.com/MalcolmRobb/OmegaBCircuits/blob/master/1800-1849.pdf

The 4 lambda sensors are P32, P36, P79 and P91. Since you're only getting issues with one of them, it's unlikely to be the 12V feed (the grey wire) to the heater elephant (from X3)

It could be the car loom side connector pin 1 or pin 2 to the lambda sensor. I know you've contitnuity checked it to X85pin1&2, but it could be that the connector pin itself is 'splayed' apart. When you con-check it by poking the AVO probe up it, it connects. But when you plug it into the lambda sensor connector it fails to mate. That would also give you the fault if you swapped the banks, since the loom side pin still wouldn't connect to the other sensor.

To check this, plug all the sensors back in and continuity check from X85  pin 2 to X85 pin 34 (or pin 18 or pin 50). That buzzes through two lambda sensors heaters (P79 and P91). If it's open circuit then it confirms a wiring loom fault. If that checks out, then the connector and loom are OK, and it's looking like a duff ECU.   

You also have an error or typo in you initial con checking. The sensor (not heater) terminals on X85 are pins 7(Brown and Black) and 39(Blue), not 7 and 9. However, since it's moaning about the heater not the sensor, chances are this is not the fault anyway.
« Last Edit: Yesterday at 10:42:00 by LC0112G »
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Migalot

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Re: What does this pipe do?
« Reply #104 on: Yesterday at 12:31:13 »

This is the circuit you need :

https://github.com/MalcolmRobb/OmegaBCircuits/blob/master/1800-1849.pdf

The 4 lambda sensors are P32, P36, P79 and P91. Since you're only getting issues with one of them, it's unlikely to be the 12V feed (the grey wire) to the heater elephant (from X3)

It could be the car loom side connector pin 1 or pin 2 to the lambda sensor. I know you've contitnuity checked it to X85pin1&2, but it could be that the connector pin itself is 'splayed' apart. When you con-check it by poking the AVO probe up it, it connects. But when you plug it into the lambda sensor connector it fails to mate. That would also give you the fault if you swapped the banks, since the loom side pin still wouldn't connect to the other sensor.

To check this, plug all the sensors back in and continuity check from X85  pin 2 to X85 pin 34 (or pin 18 or pin 50). That buzzes through two lambda sensors heaters (P79 and P91). If it's open circuit then it confirms a wiring loom fault. If that checks out, then the connector and loom are OK, and it's looking like a duff ECU.   

You also have an error or typo in you initial con checking. The sensor (not heater) terminals on X85 are pins 7(Brown and Black) and 39(Blue), not 7 and 9. However, since it's moaning about the heater not the sensor, chances are this is not the fault anyway.

Thanks. I changed the ECU and still get the problem, so that can be discounted.
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