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tencentlife
Samba Member
Joined: May 02, 2006
Posts: 10147
Location: Abiquiu, NM, USA
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 Posted: Thu Oct 24, 2024 8:44 am Post subject: Re: Possible bad O2 sensor? |
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You obviously understand EFI and the lambda cycle better than most, so you'll understand the nitty-gritty I get into here:
https://intrepidoverland.com/why-good-electrical-grounding-matters/
Pay particular attention to the last few paragraphs about VW's lame-ass battery grounding method with reference to the exact behavior you're seeing yourself.
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AirCooledCurtis
Samba Member
Joined: June 26, 2012
Posts: 103
Location: Portland, OR.
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| Posted: Thu Oct 24, 2024 9:50 am Post subject: Re: Possible bad O2 sensor? |
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| tencentlife wrote: |
You obviously understand EFI and the lambda cycle better than most, so you'll understand the nitty-gritty I get into here:
https://intrepidoverland.com/why-good-electrical-grounding-matters/
Pay particular attention to the last few paragraphs about VW's lame-ass battery grounding method with reference to the exact behavior you're seeing yourself. |
Great article, I'll go through all the grounds. I did touch a few of the main power wires because they had inferior terminals replaced. All of the connections that had been messed with should now have the proper terminals but there's a chance I missed something while putting everything back together.
With the o2 disconnected, I get no continuity from the signal to ground with the ECU unplugged. Good. With the ECU plugged in I seem to be getting 213k ohms. Is this normal? |
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tencentlife
Samba Member
Joined: May 02, 2006
Posts: 10147
Location: Abiquiu, NM, USA
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| Posted: Thu Oct 24, 2024 10:42 am Post subject: Re: Possible bad O2 sensor? |
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| Quote: |
| With the o2 disconnected, I get no continuity from the signal to ground with the ECU unplugged. Good. With the ECU plugged in I seem to be getting 213k ohms. Is this normal? |
Probably, but not something I've ever specifically tested. There has to be some connection between them internally, so some ohm value would be expected. I'm not near my shop this week to check that.
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Please don't PM here, I will not reply.
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DigiMatrix
Samba Member
Joined: April 20, 2010
Posts: 495
Location: Up North Canada
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| Posted: Thu Oct 24, 2024 11:16 am Post subject: Re: Possible bad O2 sensor? |
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| AirCooledCurtis wrote: |
| With the ECU plugged in I seem to be getting 213k ohms. Is this normal? |
When I measure 2 spare ECU's on the bench between pin 2 and pin 19 I get 161.2 K ohms and 161.0 K ohms.
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_________________
'91 Syncro Westfalia
soon to be 2.5 liter stroker WBX 10:1 comp
Digifant ECU with knock sensor and custom
cylinder selective knock control by me |
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AirCooledCurtis
Samba Member
Joined: June 26, 2012
Posts: 103
Location: Portland, OR.
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| Posted: Thu Oct 24, 2024 11:26 am Post subject: Re: Possible bad O2 sensor? |
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| DigiMatrix wrote: |
| AirCooledCurtis wrote: |
| With the ECU plugged in I seem to be getting 213k ohms. Is this normal? |
When I measure 2 spare ECU's on the bench between pin 2 and pin 19 I get 161.2 K ohms and 161.0 K ohms. |
Thanks, that might be pointing towards the issue. |
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DigiMatrix
Samba Member
Joined: April 20, 2010
Posts: 495
Location: Up North Canada
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| Posted: Thu Oct 24, 2024 11:52 am Post subject: Re: Possible bad O2 sensor? |
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| AirCooledCurtis wrote: |
| DigiMatrix wrote: |
| AirCooledCurtis wrote: |
| With the ECU plugged in I seem to be getting 213k ohms. Is this normal? |
When I measure 2 spare ECU's on the bench between pin 2 and pin 19 I get 161.2 K ohms and 161.0 K ohms. |
Thanks, that might be pointing towards the issue. |
You're welcome. If your resistance at the ECU between pin 2 and pin 19 checks out the same as my checks, then I would check the resistance between the ECU plug pin 2 and the O2 sensor end of the wire and between pin 19 and where it terminates. I think you'll find your problem. 52K ohms is quite a difference. Bad crimp on the new O2 wiring harness?
_________________
_________________
'91 Syncro Westfalia
soon to be 2.5 liter stroker WBX 10:1 comp
Digifant ECU with knock sensor and custom
cylinder selective knock control by me |
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AirCooledCurtis
Samba Member
Joined: June 26, 2012
Posts: 103
Location: Portland, OR.
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| Posted: Fri Oct 25, 2024 7:40 am Post subject: Re: Possible bad O2 sensor? |
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| pulled the ECU and checked between pin 2 and 19, 216k ohms. I've got a 022D coming in the mail now, so hopefully that fixes it. |
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DigiMatrix
Samba Member
Joined: April 20, 2010
Posts: 495
Location: Up North Canada
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| Posted: Fri Oct 25, 2024 7:49 am Post subject: Re: Possible bad O2 sensor? |
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| AirCooledCurtis wrote: |
| pulled the ECU and checked between pin 2 and 19, 216k ohms. I've got a 022D coming in the mail now, so hopefully that fixes it. |
Was it a "D" version that you had in there? If so, don't throw it out it can probably be fixed. Otherwise I'll buy it for parts.
_________________
_________________
'91 Syncro Westfalia
soon to be 2.5 liter stroker WBX 10:1 comp
Digifant ECU with knock sensor and custom
cylinder selective knock control by me |
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AirCooledCurtis
Samba Member
Joined: June 26, 2012
Posts: 103
Location: Portland, OR.
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| Posted: Fri Oct 25, 2024 8:59 am Post subject: Re: Possible bad O2 sensor? |
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| DigiMatrix wrote: |
| AirCooledCurtis wrote: |
| pulled the ECU and checked between pin 2 and 19, 216k ohms. I've got a 022D coming in the mail now, so hopefully that fixes it. |
Was it a "D" version that you had in there? If so, don't throw it out it can probably be fixed. Otherwise I'll buy it for parts. |
it's a previously reman'd Bosch one, no sticker, but has a removable chip, so I'm pretty sure if it's just the removable chip that matters. |
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AirCooledCurtis
Samba Member
Joined: June 26, 2012
Posts: 103
Location: Portland, OR.
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| Posted: Fri Oct 25, 2024 9:27 am Post subject: Re: Possible bad O2 sensor? |
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| Is there anywhere on the ECU board that is known to cause issues, or any components that are o2 related? I fixed a Volvo LH2.4 ecu recently that had a fried injector transistor so I can kinda find my way around a circuit. |
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zerotofifty
Samba Member
Joined: December 27, 2003
Posts: 3793
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| Posted: Fri Oct 25, 2024 9:57 am Post subject: Re: Possible bad O2 sensor? |
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| AirCooledCurtis wrote: |
| Is there anywhere on the ECU board that is known to cause issues, or any components that are o2 related? I fixed a Volvo LH2.4 ecu recently that had a fried injector transistor so I can kinda find my way around a circuit. |
If the brain box is not properly secured, mounted well, then movement between it and the big connector can lead to cracks in the traces on the brains board near the connector If the cable is yanked or had stuff push on it wrong, that can do it also. I have heard of that happening on our vans, but not experienced it.
Dead power transistors for injectors can be caused by a short of the injector wires, dont short the injectors. I had that happen on a Porsche 914 brain, opps!!! |
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DigiMatrix
Samba Member
Joined: April 20, 2010
Posts: 495
Location: Up North Canada
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| Posted: Fri Oct 25, 2024 12:58 pm Post subject: Re: Possible bad O2 sensor? |
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| AirCooledCurtis wrote: |
it's a previously reman'd Bosch one, no sticker, but has a removable chip, so I'm pretty sure if it's just the removable chip that matters. |
Removable chip is one of 3 possible "D" versions, so yes, it is definitely a "D" version.
_________________
_________________
'91 Syncro Westfalia
soon to be 2.5 liter stroker WBX 10:1 comp
Digifant ECU with knock sensor and custom
cylinder selective knock control by me |
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AirCooledCurtis
Samba Member
Joined: June 26, 2012
Posts: 103
Location: Portland, OR.
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| Posted: Fri Oct 25, 2024 1:04 pm Post subject: Re: Possible bad O2 sensor? |
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| DigiMatrix wrote: |
| AirCooledCurtis wrote: |
it's a previously reman'd Bosch one, no sticker, but has a removable chip, so I'm pretty sure if it's just the removable chip that matters. |
Removable chip is one of 3 possible "D" versions, so yes, it is definitely a "D" version. |
Actually not so sure. It's a socketed 24 pin chip (not 28), I'm confident it's just a 022, it doesn't have the same square micro processors as the 022D, it has the usual IC rectangular chips.
I just want to confirm with someone with a 022 (not D) that pin 2 to 19 is not anywhere near 213-216k ohms. I'm done poking around with this ECU, I can't find any cracked solder joints, caps, overheated resistors etc. I've yet to see anyone with this particular failure with the ECU. |
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DigiMatrix
Samba Member
Joined: April 20, 2010
Posts: 495
Location: Up North Canada
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| Posted: Fri Oct 25, 2024 1:26 pm Post subject: Re: Possible bad O2 sensor? |
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The 2 spare ECU's I gave the resistance reading on were "D" versions. I don't have any of the others to measure. I'm not familiar with the non 'D" versions other than I know they don't run the Motorola 68HC11A1FN processor that the "D" versions do.
_________________
_________________
'91 Syncro Westfalia
soon to be 2.5 liter stroker WBX 10:1 comp
Digifant ECU with knock sensor and custom
cylinder selective knock control by me |
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DigiMatrix
Samba Member
Joined: April 20, 2010
Posts: 495
Location: Up North Canada
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| Posted: Fri Oct 25, 2024 1:56 pm Post subject: Re: Possible bad O2 sensor? |
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| AirCooledCurtis wrote: |
I just want to confirm with someone with a 022 (not D) that pin 2 to 19 is not anywhere near 213-216k ohms. I'm done poking around with this ECU, I can't find any cracked solder joints, caps, overheated resistors etc. I've yet to see anyone with this particular failure with the ECU. |
Can you follow the PCB trace from pin 2 to the first resistor in the circuit - it should be a 10K resistor (brn/blk/blk/red/brn). The next resistor that the first resistor is connected to is the important one. Can you let me know what it's color code is? I will do a circuit simulation to see what I think the reading should be based on it's value
When I did this with the "D" version I got 160.25 ohms which very close to what I measured on my 2.
_________________
_________________
'91 Syncro Westfalia
soon to be 2.5 liter stroker WBX 10:1 comp
Digifant ECU with knock sensor and custom
cylinder selective knock control by me |
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RawUmber
Samba Member
Joined: June 23, 2019
Posts: 306
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| Posted: Fri Oct 25, 2024 3:26 pm Post subject: Re: Possible bad O2 sensor? |
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| AirCooledCurtis wrote: |
| I just want to confirm with someone with a 022 (not D) that pin 2 to 19 is not anywhere near 213-216k ohms. |
An ohm reading of either 191K or 216K is normal for an 022. |
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AirCooledCurtis
Samba Member
Joined: June 26, 2012
Posts: 103
Location: Portland, OR.
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| Posted: Sat Oct 26, 2024 2:06 pm Post subject: Re: Possible bad O2 sensor? |
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| DigiMatrix wrote: |
| AirCooledCurtis wrote: |
I just want to confirm with someone with a 022 (not D) that pin 2 to 19 is not anywhere near 213-216k ohms. I'm done poking around with this ECU, I can't find any cracked solder joints, caps, overheated resistors etc. I've yet to see anyone with this particular failure with the ECU. |
Can you follow the PCB trace from pin 2 to the first resistor in the circuit - it should be a 10K resistor (brn/blk/blk/red/brn). The next resistor that the first resistor is connected to is the important one. Can you let me know what it's color code is? I will do a circuit simulation to see what I think the reading should be based on it's value
When I did this with the "D" version I got 160.25 ohms which very close to what I measured on my 2. |
So confirmed on the 10k. The next one reads 206k (makes sense, the other end measures 0 ohms to pin 19) but the 5 band code looks like red-grey-violet- orange then brown for the tolerance I believe. This puts it in the 280k range being red-grey. If the grey was black, then it'd be 207k. It's clearly not red-black.
Another edit, there's a 0.1 micro farad cap in parallel with the resistor so the reading will be off. It's a 287k resistor.
I also cleaned all grounds and major power connections this afternoon. No difference. It'll still go stupid lean on throttle and die when it enters closed loop. Disconnect the o2 and it'll not run amazing but it'll not die on throttle. While sustaining throttle after startup, I can see the AFM sweeper arm sustain a fixed position as it'll cut out as the mixture goes way lean, so the AFM surely isn't the issue, the voltage output has to be consistent as it leans out. |
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DigiMatrix
Samba Member
Joined: April 20, 2010
Posts: 495
Location: Up North Canada
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| Posted: Sun Oct 27, 2024 5:38 pm Post subject: Re: Possible bad O2 sensor? |
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| AirCooledCurtis wrote: |
| DigiMatrix wrote: |
| AirCooledCurtis wrote: |
I just want to confirm with someone with a 022 (not D) that pin 2 to 19 is not anywhere near 213-216k ohms. I'm done poking around with this ECU, I can't find any cracked solder joints, caps, overheated resistors etc. I've yet to see anyone with this particular failure with the ECU. |
Can you follow the PCB trace from pin 2 to the first resistor in the circuit - it should be a 10K resistor (brn/blk/blk/red/brn). The next resistor that the first resistor is connected to is the important one. Can you let me know what it's color code is? I will do a circuit simulation to see what I think the reading should be based on it's value
When I did this with the "D" version I got 160.25 ohms which very close to what I measured on my 2. |
So confirmed on the 10k. The next one reads 206k (makes sense, the other end measures 0 ohms to pin 19) but the 5 band code looks like red-grey-violet- orange then brown for the tolerance I believe. This puts it in the 280k range being red-grey. If the grey was black, then it'd be 207k. It's clearly not red-black.
Another edit, there's a 0.1 micro farad cap in parallel with the resistor so the reading will be off. It's a 287k resistor.
I also cleaned all grounds and major power connections this afternoon. No difference. It'll still go stupid lean on throttle and die when it enters closed loop. Disconnect the o2 and it'll not run amazing but it'll not die on throttle. While sustaining throttle after startup, I can see the AFM sweeper arm sustain a fixed position as it'll cut out as the mixture goes way lean, so the AFM surely isn't the issue, the voltage output has to be consistent as it leans out. |
Sorry I was away for the weekend and just got home. Using a value of 287K for the resistor, I get a reading of 218.3 K ohms in the simulator, so not too far from what you measured. And yes in parallel with the 0.1uf cap
_________________
_________________
'91 Syncro Westfalia
soon to be 2.5 liter stroker WBX 10:1 comp
Digifant ECU with knock sensor and custom
cylinder selective knock control by me |
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AirCooledCurtis
Samba Member
Joined: June 26, 2012
Posts: 103
Location: Portland, OR.
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| Posted: Mon Oct 28, 2024 5:34 am Post subject: Re: Possible bad O2 sensor? |
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| DigiMatrix wrote: |
| Sorry I was away for the weekend and just got home. Using a value of 287K for the resistor, I get a reading of 218.3 K ohms in the simulator, so not too far from what you measured. And yes in parallel with the 0.1uf cap |
Fantastic, thank you. I was just going to head out now and fiddle some more. I'm going to toss in a better battery, and clean the transmission to chassis ground strap. I'm not getting any voltage drop while the van is off from the battery to the alternator. |
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AirCooledCurtis
Samba Member
Joined: June 26, 2012
Posts: 103
Location: Portland, OR.
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| Posted: Mon Oct 28, 2024 7:41 am Post subject: Re: Possible bad O2 sensor? |
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| I think it's fixed. Only swapped in the battery from my Volvo 240, and cleaned the transaxle to chassis ground which was not dirty. I'm getting 14.6-14.7V charging though which is high but also every Vanagon owner's dream, the old battery was not anywhere near that. This battery did pass the load test at AutoZone last month. |
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