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Old 19th July 2012, 18:39   #1
Game-R
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Diagnosing 90-91 Error Code

A friend of mine pulled out these error codes from my 2001 black beauty which I had just acquired for 6 months:

Code:
 # ERRORS DETAILS - DTC(hex)/PARAM(hex)
---------------------------------------------------------------------------------------------------------------------------
DME   ->  90/82 - Function, oxygen-sensor control, bank 1
          91/82 - Function, oxygen-sensor control, bank 2
          Shadow-memory:
          8F/00 - Electronics-box fan
          8F/00 - Electronics-box fan
          8F/00 - Electronics-box fan
          8F/00 - Electronics-box fan
          8F/00 - Electronics-box fan
          8F/00 - Electronics-box fan
          8F/00 - Electronics-box fan
          10/00 - Signal, crankshaft sensor
          10/00 - Signal, crankshaft sensor
          10/00 - Signal, crankshaft sensor
          01/00 - Fuel-pump relay
          01/00 - Fuel-pump relay
          01/00 - Fuel-pump relay
          01/00 - Fuel-pump relay
          01/00 - Fuel-pump relay
Reading from all the previous threads in diagnosing this issue, most were pointing fault at either the exhaust cat oxygen sensors, the MAFs or the fuel pump and its circuits.
Seeing that neither the MAFs nor the cat oxygen sensors were flagging errors on the system, that ruled out those possibilities. Added to that, according to my friend, it is weird (or rare) that both fuel controls on both banks would throw errors at the same time.
The fuel-pump relay was flagged in the system, but it was in the shadow memory, and wasn't a present error at the time my friend was scanning my car. So its doubtful that is the cause.

There was one clue to diagnosing this errors though. The few friends who were present then mentioned that the exhaust fumes smelled somewhat "rich". I too have been noticing that in the weeks leading up, but I assumed that it was because at the time it was the cold engine start. By deducing this, the only logical theory as to what is causing the engine to run rich would be the fuel pressure control may have gone and the fuel system is over-pressured. Has anyone experienced this before or have any suggestions as to what might be the cause?
Much appreciated

If it would be of any help, the remainder of the errors that was pulled from my system are as follows:

Code:
EWS   ->  0F/23 - Power on reset
          23/23 - Toleration of changing code increased, key 2

ABS   ->  1F/01 - Wheel speed sensor rear right, open circuit

LEW   ->  09/57 - No CAN message (ASC)

IKE   ->  BF/88 - Internal fault, EEPROM checksum, coding incorrect/incomplete

LCM   ->  Shadow-memory:
          5B/01 - Level washer fluid
          60/01 - Engine oil level, thermal sensor TOG
          99/03 - Licence plate light

ZKE   ->  AD/24 - Short circuit mirror motor vertical, passenger's door
          AC/08 - Open circuit mirror motor vertical, passenger's door
          94/21 - DWA-LED: open circuit or cable DWAL, KL30
          Shadow-memory:
          93/25 - Power up from the GM III
          8B/02 - DWA-Alarm: rear window or interior security
          83/22 - DWA-Alarm: door contact, driver's door

BMBT  ->  0B/1F - Connector monitor UB, open circuit
          01/03 - Watchdog reset

RDC   ->  0A/80 - Speed signal pulse RR
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Old 19th July 2012, 20:32   #2
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Tons of things could cause this,air leaks bad mafs or old haggard O2 sensors. Need a bit more to go on. Do you know how to do what we call a MAF test? With tyhe software you pulled the codes with can you view any live data?
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Old 19th July 2012, 23:07   #3
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As to your fuel pressure theory, the pressure regulator has a schraeder valve (sp?) that is not hard to access, underneath the drivers (Left front) door. remove the panel and you'll see the valve staring you in the face. ~4.5 bar @idle and ~5 bar when giving gas.

You didn't mention driving problems. Does it run rough, idle rough or "hunt"

Have you done any work recently on it that you could have left something like a vacuum line unattached etc?
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Old 20th July 2012, 01:29   #4
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If you mean the OBD data, no. Strangely his software wasn't able to give that readout. But air leaks would create a more lean fuel mix and faulty MAFs and oxyen sensors would show up with separate error codes in the system, right?

No. Before my friend pulled out the error codes, I simply had no idea that something was up. The only thing I did notice was the slight lackluster performance and a less noticeable growl at full throttle, which I assumed was air filters needing some cleaning. Engine and power delivery is smooth and nothing out of the ordinary. And there wasn't any servicing done underneath the car during the period the problem surfaced.

Last edited by Game-R; 20th July 2012 at 01:32.
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Old 20th July 2012, 01:49   #5
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The lean rich question we can only answer by viewing data. Air leaks are lean by nature but how the O2s respond is one variable and some leaks only happen at certain times which can leave the car rich at other times. The way that the crankcase vents, makes leaks there smell rich from oil saturated air.
Have you cleared those codes and seen if they came back? Was your SES light on?
Bad mafs generally don't throw codes, and bad O2s throw a code if they break but often just lie about how much air is present, which just richens the car enough to make the ECU think everything is fine. Remember high performance engine so on this engine you must catch it way before it breaks. Not seen very many codes that say "not quite perfect".
We need to gather more info so I ask again MAF test? If you don't know I will explain.
Clear the codes and see if they return if you have not.
Your symptoms appear to be something else if it turns out you have no codes at all and do well in the MAF test. Do you feel hesitation down low in the rpm band?
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Old 20th July 2012, 04:09   #6
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Quote:
Originally Posted by Game-R View Post
But air leaks would create a more lean fuel mix and faulty MAFs and oxyen sensors would show up with separate error codes in the system, right?

.
ABSOLUTELY NOT!

You are falling into the 'trap' of most backyard mechanics- thinking the code tells you what to replace!

Like "misfire must be sparkplugs, coil or wires"

'O2 sensor code must be O2 sensor'

or "fuel control must be fuel control"

Whatever you do, and you have some good advice so far, dont assume lack of a code means those items MUST be good.

A
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Old 20th July 2012, 05:19   #7
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Quote:
Originally Posted by Sailor24 View Post
The lean rich question we can only answer by viewing data. Air leaks are lean by nature but how the O2s respond is one variable and some leaks only happen at certain times which can leave the car rich at other times. The way that the crankcase vents, makes leaks there smell rich from oil saturated air.
Have you cleared those codes and seen if they came back? Was your SES light on?
Bad mafs generally don't throw codes, and bad O2s throw a code if they break but often just lie about how much air is present, which just richens the car enough to make the ECU think everything is fine. Remember high performance engine so on this engine you must catch it way before it breaks.
We need to gather more info so I ask again MAF test? If you don't know I will explain.
Clear the codes and see if they return if you have not.
Your symptoms appear to be something else if it turns out you have no codes at all and do well in the MAF test. Do you feel hesitation down low in the rpm band?
Like I said, there was absolutely no clue that I was having a problem with the car. No warning lights. No hesitation or any other weird engine behavior, except the subjective feeling of lackluster power. I drive the car most of the time in the lower half RPMs so I can't tell if high end power has been affected.

The code readout I posted above is what we got out from the system immediately after clearing the codes. Just 90 & 91 were constant errors. The remainder are in the memory.

The MAFs have been replaced by the previous owner not too long before he sold the car, thus they are pretty low in my list of suspects. I believe The MAF test is to unplug them while the engine is running? If so, I won't be able to do that until I can get hold of a scanner or see when my friend would be available since there is no physical way of telling if the errors have stopped.
Oxygen sensors though are way lower on my list, because of the odds for both banks to fail at the same period. Should one oxygen sensor generate incorrect readings it would likely only trigger one bank to flag the error, right?

I'm currently trying to arrange with a specialist garage to help diagnose the problem, but trying to book an appointment in their busy schedule has been difficult so far. Hence, my spare time in trying to diagnose this.

Quote:
Originally Posted by ard View Post
ABSOLUTELY NOT!

You are falling into the 'trap' of most backyard mechanics- thinking the code tells you what to replace!

Whatever you do, and you have some good advice so far, dont assume lack of a code means those items MUST be good.

A
Hence, why I'm asking in the boards here I am only running only on assumptions and not a bulletproof case in identifying the problem. I needed advice from experienced members if I could trust the lack of errors in the system in making my diagnosis, which you have just provided.

Last edited by Game-R; 20th July 2012 at 05:27.
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Old 20th July 2012, 06:42   #8
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If you cleared that code and it came back that fast it would be trigger the light. My guess would be you did not clear the codes, because if it came back on in the first drive cycle it would likely do it again within the next two cycles which would trigger the light.
Maf test is not unplugging them. read this
How to test the MAFs yourself and How MAFs work
Then you will also need to know how to access the OBC it is the second half of this post
Gadget Freaks II: Fun you never knew you could have [secret menu]

Edit:Considering your shadow codes and a recent thread check in the trunk at the fuses on the right side. Do you have a big black relay closest to the front?

Last edited by Sailor24; 20th July 2012 at 06:57.
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Old 20th July 2012, 06:54   #9
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Quote:
Originally Posted by Game-R View Post
I believe The MAF test is to unplug them while the engine is running? If so, I won't be able to do that until I can get hold of a scanner or see when my friend would be available since there is no physical way of telling if the errors have stopped.
I believe the method Sailor is referring to is the ever famous "secret menu" on the cluster.

Quote:
1) Key to ignition pos 2 (no need to start engine).
2) Fasten the seat belt to get rid of the "Fasten Seat Belt" message.
3) Press the right button on the instrument panel, and hold it until "TEST-NR. 01" comes up (5 to 10 seconds).
4) Press the left button on the instrument panel, and the vehicle id comes up (last 7 digits of VIN).
5) Add up the last 5 digits to get the "unlock code", e.g. the unlock code for "AB12345" would be 15 (1+2+3+4+5).
6) Repeatedly press the right button until "TEST-NR. 19" appears.
7) Press left button -> "LOCK : ON"
8) Repeatedly press left button until "LOCK : xx" appears, where "xx" is your unlock code.
9. Press the right button. All modes are unlocked now.
Now, press the right key until you get to test nr4, the press the left key twice until you see VBR L/H

Full throttle til redline in third gear (SAFETY FIRST) and then report back with your max reading.

With new mafs, may not mean as much, but there you are.

Last edited by bibledriver; 21st July 2012 at 06:26.
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Old 21st July 2012, 03:34   #10
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sailor, what is your take on the the common 90/91 code? The normal description is "fuel control - bank x" but the software used by the OP above adds a new wrinkle by describing it as "function - O2 sensor control bank x".
So does it indicate a fuel supply problem or an O2 sensor problem or a fuel supply problem detected by the O2 sensors?
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