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Discussion Starter · #1 ·
I’ve been trying to chase problems on this car for the past few weeks and more problems keep happening. It started with my intake manifold runner not opening/closing when it needed to and it was misfiring then a ton of circuitry problems started happening. I’ve replace my DME already so it’s not that, verified it with both of them that it still happened. Every code that’s came up (in order of when they happened) is
  • P1512 Disa (Intake manifold runner) circuit voltage low
  • P0132 O2 sensor high circuit voltage (b1s1)
  • P1343 misfire w fuel cut cyl 1
  • P1345 misfire w fuel cut cyl 2
  • P1347 misfire w fuel cut cyl 3
  • P0155 O2 circuit heater circuit (b2s1)
  • P0174 system too lean (bank 2)
  • P0335 Crankshaft Position Sensor "A" Circuit Malfunction
Lots of circuit problems with problems that look like they come from it. My question is what could cause all these circuit problems? My first guess was ecu so I’ve tried different software and a whole new ecu, neither worked. I’ve replaced the disa and that didnt do it either. Does a lot of wiring problems always happen all at once? Hasn’t been in any water damage. Where do I start looking now?
 

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I would start by checking the wiring to the oxygen sensors.
Carefully.
And check the 5 fuses in the compartment in with the DME.
If you can't find damage, then next would be confirming that the
o2 sensors are getting heater voltage,
and then change the precat sensors if they are.

DISA voltage can mean a short, but if I remember, can also be
an open, so check that wiring carefully, too.

And the ubiquitous air leaks, of course. Misfire with fuel cut
would make me check plugs, coils and the harness, but not
particularly expect to find anything wrong. Are your plugs recent?

Has a mouse family taken up residence in your DME bin?

for starters,

t
 

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'03 330i M-Sport Touring
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As TobyB mentioned, O2 sensors could be a likely cause for most of those fault codes, apart from maybe the DISA and Crankshaft sensor faults.

A faulty 02 sensor caused misfire codes and lean codes on my car which have gone away after replacing my post cat 02 sensors (I had different fault codes though, so yours are probably the precat ones).
 

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Discussion Starter · #4 ·
I would start by checking the wiring to the oxygen sensors.
Carefully.
And check the 5 fuses in the compartment in with the DME.
If you can't find damage, then next would be confirming that the
o2 sensors are getting heater voltage,
and then change the precat sensors if they are.

DISA voltage can mean a short, but if I remember, can also be
an open, so check that wiring carefully, too.

And the ubiquitous air leaks, of course. Misfire with fuel cut
would make me check plugs, coils and the harness, but not
particularly expect to find anything wrong. Are your plugs recent?

Has a mouse family taken up residence in your DME bin?

for starters,

t
Both precat sensors are brand new as of a couple months ago, spark plugs brand new at same time, coil packs were inspected and not the cause, disa is like 2 weeks old because I got it warrantied after this happened, no mice in garage and I already got a new dme that causes the same problems. I have a closed loop in bank 2 but bank 1 is open due to system error and o2 b1s1 just stays at 1.275 volts. I swapped them around and b1s1 is still at constant 1.275 volts. I think I inspected the fuses last week but I’ll go through them more thoroughly. I’ll get back to you on fuses and multimeter tests, thanks for the reply
 

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2000 E46 323i, 3.0L and 2.0L Z3's
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I agree with @TobyB. Your B1S1 O2 sensor is on the fritz and the B2S1 O2 sensor has no heating. Check supply fuses and wiring. Sometimes the wiring gets out of place and melts against the exhaust pipe/Cat's/Header and causes these sorts of problems. The Pre-Cat's have been changed recently. Did the wiring go back correctly?

Also check your fuel trims. Probably best done after you get the pre-cat O2 sensors working again. If any of the 4 fuel trims are >8% then you likely have problems to find. Read: Fuel trims, lean codes, misfires and how to diagnose...
 

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Discussion Starter · #6 ·
I agree with @TobyB. Your B1S1 O2 sensor is on the fritz and the B2S1 O2 sensor has no heating. Check supply fuses and wiring. Sometimes the wiring gets out of place and melts against the exhaust pipe/Cat's/Header and causes these sorts of problems. The Pre-Cat's have been changed recently. Did the wiring go back correctly?

Also check your fuel trims. Probably best done after you get the pre-cat O2 sensors working again. If any of the 4 fuel trims are >8% then you likely have problems to find. Read: Fuel trims, lean codes, misfires and how to diagnose...
I replaced the valve cover and it didn’t have a spot to clip in the sensors so i left them hanging. Probably melted the wires....
 

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Discussion Starter · #7 ·
I would start by checking the wiring to the oxygen sensors.
Carefully.
And check the 5 fuses in the compartment in with the DME.
If you can't find damage, then next would be confirming that the
o2 sensors are getting heater voltage,
and then change the precat sensors if they are.

DISA voltage can mean a short, but if I remember, can also be
an open, so check that wiring carefully, too.

And the ubiquitous air leaks, of course. Misfire with fuel cut
would make me check plugs, coils and the harness, but not
particularly expect to find anything wrong. Are your plugs recent?

Has a mouse family taken up residence in your DME bin?

for starters,

t
ok I checked the fuses in the dme box, but couldn’t figure out how to take the top case off, so I checked resistance for each one and it was consistently 1.7-1.9 ohms for each one. I believe that is good but correct me if I’m wrong. I also check resistance for both o2 sensor heaters and got 3.7-3.9 ohms. I couldn’t find what they should be so does that seem right? Next step is tracing the o2 sensors back further for voltage but I don’t know how to do this. Do I need to have the car on to do this or just the ignition and what should I set my multimeter to as I test where the o2 sensors plug in? Also, does a short in this wiring damage the dme so I need a new one?
 

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2001 325ci
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ok I checked the fuses in the dme box, but couldn’t figure out how to take the top case off,
though we can check fuses status in the small black box, if replacement necessary (all over 20 yrs old), i have no clue either. i asked here before but nobody seems to know(?).
oh, what's your battery voltage?
 

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2000 E46 323i, 3.0L and 2.0L Z3's
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O2 Sensor heater circuits should be less than 5 ohms, so yours are OK.

For your fuse test, put the test leads together and see what reading you are getting. The 1.7 to 1.9 ohms reading may just be a dry joint or bad lead in your test leads. A fuse should read 0 ohms or very near to it.
 

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Discussion Starter · #11 ·
O2 Sensor heater circuits should be less than 5 ohms, so yours are OK.

For your fuse test, put the test leads together and see what reading you are getting. The 1.7 to 1.9 ohms reading may just be a dry joint or bad lead in your test leads. A fuse should read 0 ohms or very near to it.
Ok I did that and they read 1.9 ohms with just test leads. So fuses are definitely fine. How do I go about checking that voltage in o2 sensor is working? Have it unplugged and put the multimeter on AC as the cars running?
 

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You can try to electrically meter the output of the sensors.

If you've got narrowband sensors, you're looking for a number that
fluctuates between below .2v and up to at max a volt.
Wideband, you should see higher.

The problem is impedance- the sensors are tiny electrical generators,
and many meters will draw too much current and short them out.

Most of us look at live data in INPA, or a 3rd party OBD tool.

fwiw,
t
 
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Discussion Starter · #13 · (Edited)
You can try to electrically meter the output of the sensors.

If you've got narrowband sensors, you're looking for a number that
fluctuates between below .2v and up to at max a volt.
Wideband, you should see higher.

The problem is impedance- the sensors are tiny electrical generators,
and many meters will draw too much current and short them out.

Most of us look at live data in INPA, or a 3rd party OBD tool.

fwiw,
t
Yes I have an OBD tool that reads the voltage. Problem is that my b1s1 just reads 1.275 volts and doesn’t ever change. I’ve switched my bank 1 and bank 2 sensors and it still reads the same voltage. Where do I look next for this problem? Fuses checked, 2 dmes have been tried I’ve looked at the wires all the way to where it enters the closed casing where it enters the dme and it’s doesn’t seem to have any problems. Could it be a ground issue somewhere? Where do I check that?
Edit: can I plug in the other o2 sensor plug and swap them to see if it’s a wiring issue?
 

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2000 E46 323i, 3.0L and 2.0L Z3's
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I’ve switched my bank 1 and bank 2 sensors and it still reads the same voltage.
A bit of clarity here please:
  • You switched the Pre-Cat B1 and B2 plugs and left the sensors where they are?
  • You switched the Pre-Cat B1 and B2 sensors in the exhaust and left the plugs where they where?
  • You switched both the Pre-Cat B1 and B2 sensors positions and plugs?
For Results:
  • The voltages at the B1 and B2 readings in the DME did not change? That is the fault did not follow the swap.
  • The voltages followed the swap that you did?
 

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Discussion Starter · #15 ·
A bit of clarity here please:
  • You switched the Pre-Cat B1 and B2 plugs and left the sensors where they are?
  • You switched the Pre-Cat B1 and B2 sensors in the exhaust and left the plugs where they where?
  • You switched both the Pre-Cat B1 and B2 sensors positions and plugs?
For Results:
  • The voltages at the B1 and B2 readings in the DME did not change? That is the fault did not follow the swap.
  • The voltages followed the swap that you did?
I switched the actual sensors from the exhaust and the voltage stayed at 1.275 volts throughout the swap. I’m wondering if I can switch the plugs to see if it follows or is that bad for the car. Also wondering if I can send the plug (no sensor) a voltage to see if my OBD reads the voltage I sent it
 

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Ok, you swapped the Sensor location but not the plugs. So, the faulty sensor was still talking to the same O2 position in the DME.

Swap the plugs and see if the fault follows the swap. If it does, then replace the O2 sensor. Best practice is to replace both O2's at the same time with Bosch sensors.
 

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Discussion Starter · #17 · (Edited)
Ok, you swapped the Sensor location but not the plugs. So, the faulty sensor was still talking to the same O2 position in the DME.

Swap the plugs and see if the fault follows the swap. If it does, then replace the O2 sensor. Best practice is to replace both O2's at the same time with Bosch sensors.
Wow, all this talk is confusing you’re right. I’m gonna explain further of what I did just to make sure you got it right. Both sensors swapped plugs and holes so the bank 2 sensor went in bank 1 and was plugged into the bank 1 sensor. I didn’t just swap holes and keep them plugged in the whole time. Also, I’m very confident it’s not the sensor because i just replaced them like 3 months ago. I also checked resistance between heater cables on both o2 sensors and it was 4 ohms so the sensors should be fine. I just checked resistance between plugs and the dme plug in (so right before the dme) and both sensors showed same resistance in ground, voltage, and heater so wiring to dme seems to work??? There’s a 4th pin on both but I’m pretty sure it’s just the other heater wire that doesn’t need to go to the dme because I couldn’t find it on the ms43 pinout. So confused how it’s even possible it’s reading 1.275 volts!!!
 

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Discussion Starter · #18 ·
Does anyone have a diagram for what all the pins on the ms43 ecu mean? I want to check resistance from the board to the connectors next but can’t find a diagram. I can only find what the plugs go to, not the actual board of the ecu.
 

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Thank you for explaining the O2 sensor swap. Yes, I'm a pedantic of bugger, but I've been caught more than once with a person writing one thing and meaning another when diagnosing car problems. That just confuses things and takes so long to sort out. So, I tend to seek clarification if the writing is not clear.

Here is one the the reference sites I use for DME connections. It's generally correct. That is, there are a few minor discrepancies depending on your engine build date. StandAlone engine swap guide

O2 sensor heater circuits should be below 5 ohms.

All 4 O2 sensor wires go to the DME.
 
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